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  • 151. Manisekaran, T.
    et al.
    Kamaraj, M.
    Sharrif, S. M.
    Joshi, S. V.
    Slurry erosion studies on surface modified 13Cr-4Ni steels: Effect of angle of impingement and particle size2007In: Journal of materials engineering and performance (Print), ISSN 1059-9495, E-ISSN 1544-1024, Vol. 16, no 5, p. 567-572Article in journal (Refereed)
    Abstract [en]

    Hydroturbine steels, such as 13Cr-4Ni martensitic steels, are generally subjected to heavy-erosive wear and loss of efficiency due to solid particulate entrainment in the water. Surface-modified steels have proven to give better performance in terms of erosive wear resistance. In the present study, an attempt is made to investigate the effect of angle of impingement and particle size on slurry-jet erosion behavior of pulsed plasma nitrided and laser hardened 13Cr-4Ni steels. Laser hardening process has shown good performance at all angles of impingement due to martensitic transformation of retained austenite. Plastic deformation mode of material removal was also an evident feature of all laser-hardened surface damage locations. However, pulsed-plasma nitrided steels have exhibited chip formation and micro-cutting mode of erosive wear. Erosion with 150-300 mu m size was twice compared to 150 mu m size slurry particulates.

  • 152.
    Markocsan, Nicolaie
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Gupta, Mohit Kumar
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Joshi, Shrikant V.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing. University West, Department of Engineering Science, Research Enviroment Production Technology West.
    Nylén, Per
    University West, Department of Engineering Science, Research Enviroment Production Technology West. University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Li, Xin-Hai
    Siemens Industrial Turbomachinery, Finspång, Sweden.
    Wigren, Jan
    GKN Aerospace,Trollhättan,Sweden.
    Liquid Feedstock Plasma Spraying: An Emerging Process for Advanced Thermal Barrier Coatings2017In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 26, no 6, p. 1104-1114Article in journal (Refereed)
    Abstract [en]

    Liquid feedstock plasma spraying (LFPS) involves deposition of ultrafine droplets of suspensions or solution precursors (typically ranging from nano- to submicron size) and permits production of coatings with unique microstructures that are promising for advanced thermal barrier coating (TBC) applications. This paper reviews the recent progress arising from efforts devoted to development of high-performance TBCs using the LFPS approach. Advancements in both suspension plasma spraying and solution precursor plasma spraying, which constitute the two main variants of LFPS, are presented. Results illustrating the different types of the microstructures that can be realized in LFPS through appropriate process parameter control, model-assisted assessment of influence of coating defects on thermo-mechanical properties and the complex interplay between pore coarsening, sintering and crystallite growth in governing thermal conductivity are summarized. The enhancement in functional performances/lifetime possible in LFPS TBCs with multilayered architectures and by incorporating new pyrochlore chemistries such as gadolinium zirconate, besides the conventional single 8 wt.% yttria-stabilized zirconia insulating ceramic layer, is specifically highlighted.

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  • 153.
    Markocsan, Nicolaie
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Gupta, Mohit Kumar
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Nylen, Per
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Joshi, Shrikant V.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Wigren, J.
    Li, X-H
    Liquid feedstock plasma spraying: an emerging processfor the next generation aircraft engines2016Conference paper (Other academic)
  • 154.
    Markocsan, Nicolaie
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Gupta, Mohit Kumar
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Nylen, Per
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Joshi, Shrikant V.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Wigren, J.
    Li, X-H
    Liquid feedstock plasma spraying as an emerging process for advanced thermal barrier coatings2016Conference paper (Other academic)
  • 155.
    Mathiyalagan, Sribalaji
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Rossetti, Matteo
    University West, Department of Engineering Science. Universita di Modena e Reggio Emilia, Via Pietro Vivarelli 10/1, 41125 Modena (ITA).
    Björklund, Stefan
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Sowers, Susanne
    Hyperion Materials & Technologies, 43085 Worthington, Ohio (USA).
    Dumm, Timothy
    Hyperion Materials & Technologies, 43085 Worthington, Ohio (USA).
    Kim, Chung
    Hyperion Materials & Technologies, 43085 Worthington, Ohio (USA).
    Joshi, Shrikant V.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    High velocity air fuel (HVAF) spraying of nickel phosphorus-coated cubic-boron nitride powders for realizing high-performance tribological coatings2022In: Journal of Materials Research and Technology, ISSN 2238-7854, Vol. 18, p. 59-74Article in journal (Refereed)
    Abstract [en]

    High velocity air fuel (HVAF) spraying is an emergent thermal spray process, which is used in this work to realize high-performance large area tribological coatings of nickel-phosphorus cladded cubic-boron nitride (c-BN) particles. To the best of authors’ knowledge, this is the first time that HVAF has been utilized for developing Ni–P coatings reinforced with c-BN (NBN). The importance of appropriate processing was highlighted by utilizing two different nozzle configurations, for which microstructure, phase analysis and hardness results demonstrates considerable differences. Furthermore, the coatings were subjected to sliding wear tests to assess their friction and wear characteristics. Post-wear SEM analysis reveals the associated wear mechanisms. Effect of annealing on tribological performance of NBN coatings was also examined, and it is shown that optimal processing can preclude the need for post-treatment. Results ensuing from this work lay the foundation for new generation of HVAF-sprayed wear resistant metal/c-BN composite coatings for diverse applications. © 2022 The Author(s)

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  • 156.
    Meghwal, Ashok
    et al.
    Surface Engineering for Advanced Materials (SEAM), Swinburne University of Technology, Hawthorn (AUS).
    Anupam, Ameey
    Surface Engineering for Advanced Materials (SEAM), Swinburne University of Technology, Hawthorn (AUS).
    Boschen, Michael
    Surface Engineering for Advanced Materials (SEAM), Swinburne University of Technology, Hawthorn (AUS).
    Singh, Surinder
    Surface Engineering for Advanced Materials (SEAM), Swinburne University of Technology, Hawthorn (AUS).
    Björklund, Stefan
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Joshi, Shrikant V.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Munroe, Paul
    iversity West, Department of Engineering Science, Trollhattan, ¨ Sweden d Materials Science and Engineering, UNSW, Sydney (AUS).
    Berndt, Christopher C.
    Surface Engineering for Advanced Materials (SEAM), Swinburne University of Technology, Hawthorn (AUS).
    Ang, Andrew Siao Ming
    Surface Engineering for Advanced Materials (SEAM), Swinburne University of Technology, Hawthorn (AUS).
    Novel Al2CoCrFeNi high-entropy alloy coating produced using suspension high velocity air fuel (SHVAF) spraying2023In: Intermetallics, ISSN 0966-9795, Vol. 163, p. 1-4, article id 108057Article in journal (Refereed)
    Abstract [en]

    Metallic coatings of Al2CoCrFeNi high entropy alloy (HEA) were deposited using the suspension high velocity air fuel spray (SHVAF) process, towards exploring its viability as a bond coat in thermal barrier coatings. The relatively high Al content promoted a BCC + B2 phase-dominated coating structure, leading to enhanced mechanical properties. The oxidized microstructure exhibited a protective Al2O3 layer with characteristics comparable to conventional bond coat alloys. 

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  • 157.
    Mi, Yongcui
    et al.
    University West, Department of Engineering Science, Division of Production Systems.
    Mahade, Satyapal
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Sikström, Fredrik
    University West, Department of Engineering Science, Division of Production Systems.
    Choquet, Isabelle
    University West, Department of Engineering Science, Division of Welding Technology.
    Joshi, Shrikant V.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Ancona, Antonio
    University West, Department of Engineering Science, Division of Production Systems. Physics Department, University of Bari, Bari (ITA).
    Conduction mode laser welding with beam shaping using a deformable mirror2022In: Optics and Laser Technology, ISSN 0030-3992, E-ISSN 1879-2545, Vol. 148Article in journal (Refereed)
    Abstract [en]

    This study explores the possibility of tailoring the fusion zone in conduction mode laser welding using a deformable mirror for beam shaping of multi-kilowatt continuous wave laser sources. Three power density distributions were shaped and used in bead on plate welding of Ti64 plates in conduction mode at three travel speeds. The effect on melt pool free surface geometry, cross section, microstructure and hardness profiles was measured and studied. It is shown that the geometry of the melt pool can be modified using a deformable mirror. A narrower and longer melt pool or a wider, shorter and shallower one were indeed obtained forming Gaussian-elliptical power density distributions oriented along and transverse to the travel direction, respectively. The latter distribution could be a favourable option for laser beam additive manufacturing as it could improve process efficiency while reducing remelting of the previous layer. This system has also a promising potential for adaptive process control since it could change fundamentally the beam shape at a rate faster than 10 ms. 

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    Optics and Laser Technology
  • 158.
    Mistri, Mourmita
    et al.
    Advanced Nanoengineering Materials Laboratory, Materials Science Programme, Indian Institute of Technology Kanpur, Uttar Pradesh 208016, India (IND).
    Joshi, Shrikant V.
    University West, Department of Engineering Science, Research Enviroment Production Technology West.
    Kar, Kamal K.
    Advanced Nanoengineering Materials Laboratory, Materials Science Programme, Indian Institute of Technology Kanpur, Uttar Pradesh 208016, India; Advanced Nanoengineering Materials Laboratory, Mechanical Engineering, Indian Institute of Technology Kanpur, Uttar Pradesh 208016, India (IND).
    Balani, Kantesh
    Materials Science and Engineering, Indian Institute of Technology Kanpur, Uttar Pradesh 208016, India (IND).
    Tribomechanical insight into carbide-laden hybrid suspension-powder plasma-sprayed Tribaloy T400 composite coatings2020In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 396, article id 125957Article in journal (Refereed)
    Abstract [en]

    Tribaloy T400 (CoCrMoSi) caters to heavy-duty industrial tribological demands, but exhibits low fracture toughness with compromised resistance to crack propagation owing to the disparity in % Laves phases. In response to this limitation, hybrid suspension-powder plasma-sprayed novel Cr3C2 (d50 of 3.8 ÎŒm)/TiC (d50 of 2.2 ÎŒm) reinforced T400 (average powder size of 10–45 ÎŒm) coatings are deposited on grit-blasted SSAB Domex®350 LA steel. Continuous, adherent and co-existing lamellar T400-carbide coatings of 100 ÎŒm thickness were revealed in microstructure analysis. Intermetallic CoMoSi/Co3Mo2Si Laves and eutectic Co7Mo6/Co2Mo7 phases in T400 in addition to Cr3C2/TiC characteristic phases are confirmed via X-ray diffraction study. T400-Cr3C2 and T400-TiC have exhibited enhancement in elastic modulus (E) by 39%, and 36%, Vickers hardness (Hv) by 68%, and 82.5%; which consequently elucidates the augmentation in plasticity index (re) by 15.7% and 26.7%, and the drop in maximum displacement amplitude (hmax) by 14.9% and 19.8%, respectively, in T400-Cr3C2 and T400-TiC with reference to T400 (E of 135.2 GPa, Hv of 6.3 GPa, re = 0.318, and hmax = 1947 nm). A subsequent surmised fretting Hertzian contact diameter in T400-Cr3C2 ( 95.43 ÎŒm)/T400-TiC ( 96.1 ÎŒm) evaluated against T400 ( 106.9 ÎŒm) from optical profilometry indicates an improved damage tolerance. A contact area-based wear model, proposed herein to assess wear on a rough surface, further justifies the wear characteristics. Furthermore, synergistic L929 cell viability is recorded in T400-Cr3C2 (by 46%) and T400-TiC (by 30%) when compared with the control (+ve) disk. To conclude, suspension-powder plasma-sprayed T400-Cr3C2/T400-TiC composite coatings allude potential application in wear-resistant articulating surfaces by eliciting significantly enhanced micro-hardness through refined microstructure retention, improved fretting wear resistance by forming protective tribofilm, and augmented cellular response. © 2020 Elsevier B.V.

  • 159.
    Mulone, Antonio
    et al.
    Chalmers University of Technology, Department of Industrial and Materials Science, Gothenburg (SWE).
    Mahade, Satyapal
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Björklund, Stefan
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Lundström, Dennis
    GKN Aerospace Engines Sweden, Trollhättan (SWE).
    Kjellman, Björn
    GKN Aerospace Engines Sweden, Trollhättan (SWE).
    Joshi, Shrikant V.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Klement, Uta
    Chalmers University of Technology, Department of Industrial and Materials Science, Gothenburg (SWE).
    Development of yttria-stabilized zirconia and graphene coatings obtained by suspension plasma spraying: Thermal stability and influence on mechanical properties2023In: Ceramics International, ISSN 0272-8842, E-ISSN 1873-3956, Vol. 49, no 6, p. 9000-9009Article in journal (Refereed)
    Abstract [en]

    This study investigated the feasibility of depositing graphene nanoplatelet (GNP)-reinforced yttria-stabilized zirconia (YSZ) composite coatings. The coatings were deposited from an ethanol-based mixed YSZ and GNP suspension using suspension plasma spraying (SPS). Raman spectroscopy confirmed the presence of GNPs in the YSZ matrix, and scanning electron microscopy (SEM) analysis revealed a desired columnar microstructure with GNPs distributed predominantly in the inter-columnar spacing of the YSZ matrix. The as-deposited YSZ-GNP coatings were subjected to different isothermal treatments—400, 500, and 600 °C for 8 h—to study the thermal stability of the GNPs in the composite coatings. Raman analysis showed the retention of GNPs in specimens exposed to temperatures up to 500 °C, although the defect concentration in the graphitic structure increased with increasing temperature. Only a marginal effect on the mechanical properties (i.e., hardness and fracture toughness) was observed for the isothermally treated coatings. 

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  • 160.
    Murray, James W.
    et al.
    University of Nottingham, Faculty of Engineering, UK.
    Leva, Alessandro
    University of Nottingham, Faculty of Engineering, UK.
    Joshi, Shrikant V.
    University West, Department of Engineering Science, Research Enviroment Production Technology West.
    Hussain, Tanvir
    University of Nottingham, Faculty of Engineering, UK.
    Microstructure and wear behaviour of powder and suspension hybrid Al2O3–YSZ coatings2018In: Ceramics International, ISSN 0272-8842, E-ISSN 1873-3956, Vol. 44, no 7, p. 8498-8504Article in journal (Refereed)
    Abstract [en]

    Abstract Suspension based plasma sprayed coatings can yield superior microstructural and tribological properties compared to conventional powder based plasma sprayed coatings. This study investigates a new hybrid method, using simultaneous spraying from powder and suspension, to produce composite coatings using alumina and yttria stabilised zirconia (YSZ), with potentially excellent wear and thermal properties. Dry sliding wear showed the alumina suspension-YSZ suspension coating yielded half the specific wear rate of the alumina powder-YSZ suspension, explained by preferential gamma alumina formation and increased porosity in the latter. Both YSZ-containing samples showed superior toughness and wear rate than simple alumina powder and suspension coatings.

  • 161.
    Ossiansson, Mattias
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Gupta, Mohit Kumar
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Löbel, M.
    Chemnitz University of Technology, Chemnitz (DEU).
    Lindner, T.
    Chemnitz University of Technology, Chemnitz (DEU).
    Lampke, T.
    Chemnitz University of Technology, Chemnitz (DEU).
    Joshi, Shrikant V.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Assessment of CrFeCoNi and AlCrFeCoNi High-Entropy Alloys as Bond Coats for Thermal Barrier Coatings2022In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 31, p. 1404-1422Article in journal (Refereed)
    Abstract [en]

    High-entropy alloys (HEAs) represent a relatively new group of multicomponent alloys that have shown great potential for applications requiring tribological and oxidation resistant properties. Consequently, thermally sprayed coatings of different HEA chemistries have received increasing research attention. In this paper, atomized equimolar CrFeCoNi and AlCrFeCoNi feedstocks were used for high velocity air-fuel spraying (HVAF) to produce overlay coatings using two different nozzle configurations. The microstructure, phase constitution and hardness of the coatings were analyzed along with the primary aim of testing the coatings for their oxidation behavior. The performance of the two HEA chemistries was compared with two commercial MCrAlY coatings that are well-established bond coat materials for thermal barrier coatings (TBCs). An investigation was conducted to test the coatings’ performance as bond coats by applying suspension plasma sprayed yttria-stabilized zirconia top coats and evaluating the thermal cycling behavior of the TBCs. The AlCrFeCoNi-coating was found to demonstrate a lower oxidation rate than the CrFeCoNi-coating. However, the AlCrFeCoNi-coating was found to form more rapid oxide scales compared with the commercial bond coat material that also contained reactive elements. © 2022, The Author(s).

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  • 162.
    Owoseni, Tunji A.
    et al.
    University West, Department of Engineering Science, Division of Production Systems. Kwara State University, Ilorin (NGA).
    Ciudad de Lara, Irene
    University West, Trollhättan (SWE).
    Mathiyalagan, Sribalaji
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Björklund, Stefan
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Joshi, Shrikant V.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Microstructure and Tribological Performance of HVAF-Sprayed Ti-6Al-4V Coatings2023In: Coatings, ISSN 2079-6412, Vol. 13, no 11, p. 1-15Article in journal (Refereed)
    Abstract [en]

    Ti-6Al-4V is a widely used titanium alloy in aviation and bio/chemical applications for its attractive mechanical and corrosion resistance properties. The use of Ti-6Al-4V as a coating for repair purposes through thermal spray techniques provides a unique productivity opportunity. A repair coating must be dense to provide the required in-service functionalities, such as resistance to wear. The High Velocity Air Fuel (HVAF) thermal spray technique deposits dense coatings with reduced concern for oxide inclusions. This work presents an investigation of the microstructure, dry sliding, and solid particle erosive wear performance of four different coatings engineered through the configuration of the nozzle of an HVAF spray gun, based on the length of the nozzle and the size of the nozzle exit. A long nozzle length and wide nozzle exit mean increased inflight dwell time and reduced average inflight temperature for the sprayed particles, respectively—a reversed configuration means the opposite. The tested coatings showed a porosity of less than 2%. The sliding and erosion wear performance of the densest of the coatings compares to that of the bulk material tested under the same conditions. Electron microscopy was used to investigate the driving mechanisms for the performance of the respective coatings. The implications of the results are discussed for the potential adoption of HVAF-sprayed coatings in metal component repair.

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  • 163. Padmavathi, C.
    et al.
    Sarin Sundar, J. K.
    Joshi, S. V.
    Rao, K. P.
    Effect of pulsed Nd: YAG laser melting treatment on microstructural and corrosion behaviour of AZ91C Mg alloy2006In: Materials Science and Technology, ISSN 0267-0836, E-ISSN 1743-2847, Vol. 22, no 5, p. 583-589Article in journal (Refereed)
    Abstract [en]

    In the present study, an attempt was made to improve the corrosion resistance and microhardness of a cast magnesium-aluminium-zinc alloy by laser surface melting. A 400 W pulsed Nd:YAG laser was used to melt and rapidly quench the surface of the cast AZ91C alloy to improve the corrosion resistance. This was evaluated using potentiodynamic polarisation and EIS studies. The microstructure of the melt pool was examined using optical microscopy and scanning electron microscopy (SEM) along with energy dispersive spectroscopy (EDS), X-ray diffraction studies (XRD) and X-ray fluorescence (XRF). The work revealed that laser melting improves the corrosion resistance of as cast AZ91C alloy because of its fine microstructure and extensive solubility of aluminium in eutectic (β phase). The microhardness of the laser surface melted layer was also increased from 74 HV to 99-124 HV. © 2006 Institute of Materials, Minerals and Mining.

  • 164. Padmavathi, C.
    et al.
    Sarin Sundar, J. K.
    Joshi, S. V.
    Rao, K. P.
    Improving wear resistance of cast AZ91C magnesium alloy by surface melting techniques2006In: Transactions of the Indian Institute of Metals, ISSN 0019-493X, Vol. 59, no 1, p. 99-106Article in journal (Refereed)
    Abstract [en]

    AZ91C cast magnesium alloy is an excellent candidate for automotive industries due to its low density. However, AZ91C alloy is not considered as suitable alloy for mechanical applications due to its low wear resistance property. In this present study, surface melting techniques were adopted to improve the wear resistance of AZ91C alloy. Gas tungsten arc with pulsing mode and pulsed laser surface melting techniques were carried out. The wear properties were evaluated from the pin-on-disc wear testing. The hardness values of the surface melted layers increased as compared with alloy in cast condition. The wear results showed that the surface melting processes has improved the wear resistance as compared with as cast. The improvement in wear resistance may be attributed due to grain refinement imparted by surface melting techniques. The wear rates of the alloy depend on hardness of alloy. The wear surface and wear debris were analyzed with optical microscopy, SEM along with EDS analysis and XRD studies for determining the mode of wear and wear mechanism. The worn surface analysis of surface melted samples were very smooth and granular peeling was hardly observed as compared to the generation of loose debris in the case of as cast alloy.

  • 165. Pardhasaradhi, S. P.
    et al.
    Venkatachalapathy, V.
    Joshi, S. V.
    Govindan, S.
    Optical diagnostics study of gas particle transport phenomena in cold gas dynamic spraying and comparison with model predictions2008In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 17, no 4, p. 551-563Article in journal (Refereed)
    Abstract [en]

    Cold gas dynamic spraying (CGDS), a relatively new thermal spraying technique has drawn a lot of attention due to its inherent capability to deposit a wide range of materials at relatively low-operating temperatures. A De Laval nozzle, used to accelerate the powder particles, is the key component of the coating equipment. Knowledge concerning the nozzle design and effect of process parameters is essential to understand the coating process and to enable selection of appropriate parameters for enhanced coating properties. The present work employs a one-dimensional isentropic gas flow model in conjunction with a particle acceleration model to calculate particle velocities. A laser illumination-based optical diagnostic system is used for validation studies to determine the particle velocity at the nozzle exit for a wide range of process and feedstock parameters such as stagnation temperature, stagnation pressure, powder feed rate, particle size and density. The relative influence of process and feedstock parameters on particle velocity is presented in this work. © ASM International 2008.

  • 166.
    Pederson, Robert
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Andersson, Joel
    University West, Department of Engineering Science, Division of Welding Technology.
    Joshi, Shrikant V.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Additive Manufacturing of High-Performance Metallic Materials2023 (ed. 1.)Book (Refereed)
  • 167.
    Pederson, Robert
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Andersson, Joel
    University West, Department of Engineering Science, Division of Welding Technology.
    Joshi, Shrikant V.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Neikter, Magnus
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Isoaho, Jerry
    GKN Aerospace Engine Systems,Trollhättan (SWE).
    Metal additive manufacturing: Motivation, process portfolio, and application potential2023In: Additive Manufacturing of High-Performance metallic Materials / [ed] Pederson, Robert, Andersson, Joel & Joshi, Shrikant V., Elsevier, 2023, 1, p. 20-40Chapter in book (Refereed)
    Abstract [en]

    The idea of adding material only where needed to manufacturesolid metallic high-performing components is intriguing andone of the main reasons for the great interest in additivemanufacturing (AM) around the world. Especially whensustainability comes into play, as in recent times more thanever, AM technology is most appropriate since it enables almostfull material utilization with minimal waste. From an economicstandpoint, this becomes particularly advantageous for moreexpensive materials such as superalloys and titanium alloys.However, the route of going from a CAD drawing of a part to anadditively manufactured final component that is qualified and inserial production involves numerous challenges. The intentionof this book is to shed light on and explain some of theassociated challenges beginning with the importance of thestarting material and how it is manufactured, i.e., wire orpowder, continuing into description of the conventional andPederson, R., Andersson, J., & Joshi, S. (2023). Additive manufacturing of high-performance metallic materials. Elsevier.Created from vast-ebooks on 2024-01-08 16:09:20. Copyright © 2023. Elsevier. All rights reserved.most commonly used AM processes, followed by postbuildtreatments and nondestructive evaluations, to eventuallyproduce the final part with mechanical performance consistentwith the application requirements. In the end, selected realindustry examples of AM parts for actual applications will bepresented

  • 168. Pemmasani, S. P.
    et al.
    Rajulapati, K. V.
    Ramakrishna, M.
    Valleti, K.
    Gundakaram, R. C.
    Joshi, S. V.
    Characterization of multilayer nitride coatings by electron microscopy and modulus mapping2013In: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 81, p. 7-18Article in journal (Refereed)
    Abstract [en]

    This paper discusses multi-scale characterization of physical vapour deposited multilayer nitride coatings using a combination of electron microscopy and modulus mapping. Multilayer coatings with a triple layer structure based on TiAlN and nanocomposite nitrides with a nano-multilayered architecture were deposited by Cathodic arc deposition and detailed microstructural studies were carried out employing Energy Dispersive Spectroscopy, Electron Backscattered Diffraction, Focused Ion Beam and Cross sectional Transmission Electron Microscopy in order to identify the different phases and to study microstructural features of the various layers formed as a result of the deposition process. Modulus mapping was also performed to study the effect of varying composition on the moduli of the nano-multilayers within the triple layer coating by using a Scanning Probe Microscopy based technique. To the best of our knowledge, this is the first attempt on modulus mapping of cathodic arc deposited nitride multilayer coatings. This work demonstrates the application of Scanning Probe Microscopy based modulus mapping and electron microscopy for the study of coating properties and their relation to composition and microstructure. © 2013 Elsevier Inc.

  • 169. Pemmasani, S. P.
    et al.
    Valleti, K.
    Gundakaram, R. C.
    Rajulapati, K. V.
    Mantripragada, R.
    Koppoju, S.
    Joshi, S. V.
    Effect of microstructure and phase constitution on mechanical properties of Ti1-xAlxN coatings2014In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 313, p. 936-946Article in journal (Refereed)
    Abstract [en]

    Monolithic TiAlN coatings with varying Al content in the range 0-65 at.% were deposited by cathodic arc evaporation. The variation in mechanical properties was studied by nanoindentation and scratch testing, and correlated with the phase constitution, grain size and residual stress. The hardness was found to be nearly stable up to Al content of 53% followed by a large drop at 65%. Depending on the stoichiometry, phase constitution and microstructure of the Ti1-xAlxN coatings, the mechanical property measurements were observed to reveal distinct trends at particular Al contents-ranging from a large scatter to clustering of data around specific values. Focused Ion Beam milling and Transmission Electron Microscopy studies showed a gradual change in microstructure, from large columnar grains in TiN to finer columns at intermediate Al content and near equiaxed, ultrafine grains with a nanocomposite structure in case of Ti0.35Al0.65N. Scratch studies revealed the deformation modes to vary with Al content, with the ductile failure modes at low Al content giving way to brittle failure at the highest Al content. Toughness studies showed a gradual increase in toughness with Al%, with the maximum seen at 53% and a moderate drop seen at 65%. The toughness shows a close dependence on the mechanical properties, phase constitution and microstructure. The study outlines the role of Al content on the microstructure of PVD TiAlN coatings and highlights the advantage of a cubic, nanocomposite structure for enhancing the toughness of these coatings. © 2014 Elsevier B.V. All rights reserved.

  • 170. Pemmasani, S. P.
    et al.
    Valleti, K.
    Ramakrishna, M.
    Rajulapati, K. V.
    Gundakaram, R. C.
    Joshi, Shrikant V.
    Structure-property correlations in cathodic arc deposited tialn coatings2012In: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 702-703, no 1, p. 967-970Article in journal (Refereed)
    Abstract [en]

    PVD hard coatings, notably transition metal nitrides and carbides, are being increasingly used by industry for improving the life and machining speeds of cutting and forming tools. There has been an increasing trend towards use of complex coatings, based on ternary and even more complex multi-component systems, as well as in novel configurations such as multilayers, superlattices, nanolayers and graded coatings, to achieve superior properties in the tool as well as the finished product. The service properties of the coatings are known to be influenced by their microstructure, phase assembly and composition, apart from the orientation and stress states which can be suitably tailored for diverse applications. In the present study, a ternary coating based on Titanium Aluminum Nitride was deposited on high speed steel substrates by cathodic arc evaporation under varied bias voltage conditions. Asdeposited coatings were characterized by X-ray diffraction, Residual Stress Analysis, Scanning Electron Microscopy (SEM), EBSD and FIB. Mechanical and tribological characteristics of the coatings were evaluated by nanoindentation and nanoscratch testing, respectively. The variations in coating hardness and adhesion with the bias voltage were studied. The changes in coating microstructure as a consequence of variation in bias voltage were also examined. Results from the above investigations are presented to illustrate how a combination of electron microscopy with nanoindentation. © (2012) Trans Tech Publications, Switzerland.

  • 171. Pulugurtha, S. R.
    et al.
    Bhat, D. G.
    Gordon, M. H.
    Shultz, J.
    Staia, M.
    Joshi, S. V.
    Govindarajan, S.
    Mechanical and tribological properties of compositionally graded CrAlN films deposited by AC reactive magnetron sputtering2007In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 202, no 4-7, p. 1160-1166Article in journal (Refereed)
    Abstract [en]

    In this work, CrAlN films with Al/Cr atomic ratios between 0.02 and 1.4 were deposited on tool inserts by AC magnetron sputtering at 5 kW for three different Ar/N-2 flow rates. The unique configuration of the inverted cylindrical magnetron sputtering (ICM-10) system enables the deposition of compositionally graded Cr-Al-N coatings under a single deposition condition. The effect of aluminum on the structural, mechanical and tribological properties of (CrAl)N coatings are reported and compared with ALCRONA and CrN coatings from Balzers. Mechanical properties have been evaluated by the microhardness indentation technique, and the hardness is 18 and 15 GPa for CrN and CrAlN films, respectively. The tribological tests have been performed using the pin-on-disc method at room temperature and 700 degrees C. The results indicate that the coefficient of friction at room temperature and 700 degrees C for all the deposited coatings, Balzers-ALCRONA and CrN fall between 0.4-0.6. The wear volume at high temperature (700 degrees C) decreases with increase in Al incorporation. Auger Electron Spectroscopy reveals that all films have about 10 at.% of oxygen. Atomic Force Microscopy showed that our films had roughness ranging from 80 to 150 nm. X-ray mapping on (Cr, Al)N coatings for different Ar/N-2 gas compositions showed transitions from cubic to hexagonal with decreasing nitrogen. (0 2007 Elsevier B.V. All rights reserved.

  • 172.
    Puneet, C.
    et al.
    International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI), Hyderabad, India.
    Valleti, Krishna
    International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI), Hyderabad, India.
    Venu Gopal, A.
    National Institute of Technology, Warangal, India.
    Joshi, Shrikant V.
    University West, Department of Engineering Science, Research Enviroment Production Technology West. International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI), Hyderabad, India.
    CrAlSiN nanocomposite thin films for high-speed machining applications2018In: Materials and Manufacturing Processes, ISSN 1042-6914, E-ISSN 1532-2475, Vol. 33, no 4, p. 371-377Article in journal (Refereed)
    Abstract [en]

    CrAlSiN nanocomposite thin films with varying film chemistry were developed on tungsten carbide (WC)specimens using cylindrical cathodic arc physical vapor deposition (c-CAPVD) technique. The physical, mechanical, and tribological properties of all the films were comprehensively investigated for arriving at the film chemistry leading to the best properties with respect to mechanical applications. The best tribo-mechanical properties were obtained in films with Cr/(AlþSi) ratio of 1.2. This coating with best properties was translated on to WC drill bits for machining tests. The Al and Si content has shown major influence on the adhesion strength and phase constitution of the films, with a considerable change in residual stress too. The superior properties achieved could be attributed to the formation of an ear-perfect nanocomposite structure, with the crystalline CrAlN phase surrounded by an amorphous Si3N4 phase. The tool life of the coated CrAlSiN tools was investigated during dry machining of EN 24material. In comparison to the tool life of an uncoated tool and a TiAlSiN-coated tool, the best CrAlSiN coatings synthesized in this study performed exceedingly well. The present study clearly demonstrates the advantages of CrAlSiN over other existing similar coatings for high-speed machining.

  • 173. Rajasekaran, B.
    et al.
    Ganesh Sundara Raman, S.
    Rama Krishna, L.
    Joshi, S. V.
    Sundararajan, G.
    Influence of microarc oxidation and hard anodizing on plain fatigue and fretting fatigue behaviour of Al-Mg-Si alloy2008In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 202, no 8, p. 1462-1469Article in journal (Refereed)
    Abstract [en]

    The present study compares the performance of microarc oxidation (MAO) and hard anodizing (HA) treated Al-Mg-Si alloy (AA6063) test samples under cyclic loading in uniaxial tension with a stress ratio of 0.1 (plain fatigue) and fretting fatigue loading. Fatigue test specimens were treated using MAO and HA techniques. MAO coated specimens were ground to reduce the surface roughness comparable with that in HA coated specimens. In that process the porous outer layer was removed. Characterization of coated and uncoated specimens was done with reference to the coating morphology, microhardness, surface roughness and residual stress. The specimens were tested under plain fatigue and fretting fatigue loading at ambient temperature. While the ground MAO coating exhibited relatively less amount of porosity, HA coating had through thickness cracks. MAO coating had compressive residual stress and it was very hard compared with HA coating. Both types of coated samples exhibited slightly higher friction force than that experienced by the uncoated specimens. Fretted region of the HA coated samples was rougher than that of the MAO coated specimens. Plain fatigue lives of both coated samples were inferior to those of the uncoated specimens. The inferior plain fatigue lives of MAO coated specimens compared with those of the substrate may be attributed to the tensile residual stresses supposedly present in the substrate leading to an early crack initiation in the substrate adjacent to the coating. As friction force of MAO coated samples was higher than that experienced by uncoated specimens, the fretting fatigue lives of MAO coated samples were slightly inferior to those of uncoated samples. As the anodized layer had preexisting through thickness cracks and strong adhesion with the substrate, cracks propagated from HA coating through the interface into the substrate easily. This may be the reason for the HA coated samples exhibiting inferior plain fatigue and fretting fatigue lives compared with MAO coated and uncoated samples. © 2007 Elsevier B.V. All rights reserved.

  • 174. Rajasekaran, B.
    et al.
    Raman, S. G. S.
    Joshi, S. V.
    Sundararajan, G.
    Effect of detonation gun sprayed Cu-Ni-In coating on plain fatigue and fretting fatigue behaviour of Al-Mg-Si alloy2006In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 201, no 3-4, p. 1548-1558Article in journal (Refereed)
    Abstract [en]

    Detonation gun spray technique was employed to coat Al-Mg-Si alloy (AA 6063) specimens with Cu-Ni-In powder. Coated samples were characterized with reference to the microstructure, porosity, residual stresses, microhardness and surface roughness. Plain fatigue (without fretting) and fretting fatigue tests were carried out at room temperature on uncoated and coated specimens. The detonation gun spray process resulted in a dense coating of almost uniform deposition with low porosity (0.3%) and good adhesion between the substrate and the coating. Under plain fatigue loading 40 mu m thick coated samples exhibited superior lives compared with uncoated and 100 mu m thick coated specimens due to the presence of higher surface compressive residual stress in the former. Delamination-induced failure resulted in inferior lives of 100 mu m thick coated specimens. Under fretting fatigue deformation 40 mu m thick coated specimens exhibited superior lives compared with 100 mu m thick coated samples owing to higher compressive residual stress at the surface and better interfacial adhesion. At 120 MPa stress level 40 pm thick coated specimens exhibited superior fretting fatigue life compared with uncoated sample and at stress levels above 120 MPa the converse was true. This was attributed to interface cracking at higher stress levels. (c) 2006 Elsevier B.V. All rights reserved.

  • 175. Rajasekaran, B.
    et al.
    Raman, S. G. S.
    Joshi, S. V.
    Sundararajan, G.
    Effect of grinding on plain fatigue and fretting fatigue behaviour of detonation gun sprayed Cu-Ni-In coating on Al-Mg-Si alloy2009In: International Journal of Fatigue, ISSN 0142-1123, E-ISSN 1879-3452, Vol. 31, no 4, p. 791-796Article in journal (Refereed)
    Abstract [en]

    Uniaxial plain fatigue and fretting fatigue tests were carried out on detonation gun sprayed Cu-Ni-In coating on Al-Mg-Si alloy samples, The samples in three conditions were considered: uncoated, as- coated and ground after coating. Ground coated specimens exhibited superior plain fatigue and fretting fatigue lives compared with uncoated and as-coated specimens. The life enhancement has been discussed in terms of surface finish and residual compressive stresses at the surface. (C) 2008 Elsevier Ltd. All rights reserved.

  • 176. Rajasekaran, B.
    et al.
    Raman, S. G. S.
    Joshi, S. V.
    Sundararajan, G.
    Effect of microarc oxidised layer thickness on plain fatigue and fretting fatigue behaviour of Al-Mg-Si alloy2008In: International Journal of Fatigue, ISSN 0142-1123, E-ISSN 1879-3452, Vol. 30, no 7, p. 1259-1266Article in journal (Refereed)
    Abstract [en]

    The objective of this work was to investigate the performance of microarc oxide coatings of two different thicknesses (40 and 100 mu m) on Al-Mg-Si alloy samples under plain fatigue and fretting Fatigue loadings. Tensile residual stress present in the substrate of 40 mu m thick coated samples induced early crack initiation in the substrate and so their plain fatigue lives were shorter than those of untreated specimens. Presence of more pores and tensile surface residual stress in 100 mu m thick coated samples caused early crack initiation at the surface leading to their inferior plain fatigue lives compared with 40 mu m thick coated samples. While the differences between the lives of coated and uncoated specimens were significant under plain fatigue loading, this was not the case under fretting fatigue loading. This may be attributed to relatively higher surface hardness of coated specimens. The performance of 40 mu m thick coated samples was better than that of 100 mu m thick coated specimens under both plain fatigue and fretting fatigue loadings. (C) 2007 Elsevier Ltd. All rights reserved.

  • 177. Rajasekaran, B.
    et al.
    Raman, S. G. S.
    Joshi, S. V.
    Sundararajan, G.
    Influence of detonation gun sprayed alumina coating on AA 6063 samples under cyclic loading with and without fretting2008In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 41, no 4, p. 315-322Article in journal (Refereed)
    Abstract [en]

    The influence of detonation gun sprayed alumina coating on Al-Mg-Si alloy (AA 6063) test samples subjected to cyclic loading with and without fretting was studied in the present work. Coated samples were grounded to have coatings of two different thickness values, 40 and 100 mu m. Both 40- and 100-mu m-thick coated specimens experienced almost the same but slightly higher friction force compared with uncoated samples. Under plain fatigue loading, 100 pm coated specimens exhibited inferior lives due to the presence of lower surface compressive residual stress compared with uncoated and 40-mu m-thick coated samples. Under fretting fatigue loading, uncoated specimens exhibited inferior lives compared with coated samples owing to the very low hardness of the uncoated specimens (80 against 1020 HV0.2). The reason for the superior fretting fatigue lives of 40-mu m-thick coated samples compared with 100-mu m-thick coated samples was the presence of relatively higher surface compressive residual stress in 40-pm-thick coated specimens. (c) 2007 Elsevier Ltd. All rights reserved.

  • 178. Rajasekaran, B.
    et al.
    Raman, S. G. S.
    Joshi, S. V.
    Sundararajan, G.
    Performance of plasma sprayed and detonation gun sprayed Cu-Ni-In coatings on Ti-6Al-4V under plain fatigue and fretting fatigue loading2008In: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 479, no 1-2, p. 83-92Article in journal (Refereed)
    Abstract [en]

    Cu-Ni-In powder was coated on Ti-6Al-4V fatigue test samples using plasma spray and detonation gun (D-gun) spray processes. Coatings were characterized in terms of microstructure, porosity, microhardness, residual stresses and surface roughness. Uniaxial plain fatigue and fretting tests were carried out at room temperature on uncoated and coated specimens. D-gun sprayed coating was dense with lower porosity compared with the plasma sprayed coating. D-gun sprayed coating was harder than the plasma sprayed coating and substrate because of its higher density and cohesive strength. Surfaces were very rough in both the coatings. While D-gun sprayed coating surface had higher compressive residual stresses, plasma sprayed coating surface exhibited lower values of compressive residual stresses and even tensile residual stresses. The ill effect of surface roughness was overcome by the beneficial influence of higher compressive residual stresses on the surface and higher surface hardness and so the D-gun sprayed samples exhibited superior plain fatigue lives compared with uncoated specimens. Though the plasma sprayed samples had relatively lower hardness, higher surface roughness and almost similar values of residual stresses on the surface compared with the uncoated specimens, they exhibited longer plain fatigue lives. This may be attributed to the layered structure of the coating. Though D-gun sprayed samples experienced higher friction forces, they exhibited superior fretting fatigue lives due to the presence of higher compressive residual stresses, higher surface hardness and higher surface roughness compared with uncoated specimens. The very rough surface of plasma sprayed samples enhanced their fretting fatigue lives compared with the uncoated samples. Higher surface hardness and higher compressive residual stress of the D-gun sprayed specimens were responsible for their superior fretting fatigue lives compared with the plasma sprayed specimens. (c) 2007 Elsevier B.V. All rights reserved.

  • 179. Raman, S. G. S.
    et al.
    Raiasekaran, B.
    Joshi, S. V.
    Sundararajan, G.
    Influence of substrate material on plain fatigue and fretting fatigue behavior of detonation gun sprayed Cu-Ni-In coating2007In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 16, no 4, p. 571-579Article in journal (Refereed)
    Abstract [en]

    Cu-Ni-In coating was formulated on two substrate materials-Ti-alloy (Ti-6Al-4V) and Al-alloy (AA 6063) fatigue test specimens using detonation gun (D-gun) spray process. Coating on both substrates was dense with low porosity, high hardness, and high surface roughness. Relatively higher surface compressive residual stress was present at the coating on Ti-alloy specimens. In case of the coating on Al-alloy samples, tensile residual stress was also present in some places. Uniaxial plain fatigue and fretting fatigue experiments were conducted on uncoated and coated specimens. The detrimental effect of life reduction due to fretting was relatively larger in the Al-alloy compared to the Ti-alloy. While Cu-Ni-In coating was found to be beneficial on the Ti-alloy, it was deleterious on the Al-alloy substrate under both plain fatigue and fretting fatigue loading. The results were explained in terms of differences in the values of surface hardness, surface roughness, surface residual stress, and friction stress.

  • 180. Rao, D. S.
    et al.
    Valleti, K.
    Joshi, S. V.
    Janardhan, G. R.
    Processing-structure-property relationships in electron beam physical vapor deposited yttria stabilized zirconia coatings2011In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films, ISSN 0734-2101, E-ISSN 1520-8559, Vol. 29, no 3, article id 031501Article in journal (Refereed)
    Abstract [en]

    The physical and mechanical properties of yttria stabilized zirconia (YSZ) coatings deposited by the electron beam physical vapor deposition technique have been investigated by varying the key process variables such as vapor incidence angle and sample rotation speed. The tetragonal zirconia coatings formed under varying process conditions employed were found to have widely different surface and cross-sectional morphologies. The porosity, phase composition, planar orientation, hardness, adhesion, and surface residual stresses in the coated specimens were comprehensively evaluated to develop a correlation with the process variables. Under transverse scratch test conditions, the YSZ coatings exhibited two different crack formation modes, depending on the magnitude of residual stress. The influence of processing conditions on the coating deposition rate, column orientation angle, and adhesion strength has been established. Key relationships between porosity, hardness, and adhesion are also presented. (C) 2011 American Vacuum Society. [DOI: 10.1116/1.3563600]

  • 181. Rathore, P. S.
    et al.
    Gulati, S.
    Li, D.
    Manivasagam, G.
    Aruna, S. T.
    Joshi, S. V.
    Szpunar, J. A.
    Comparative studies on tribocorrosion behaviour of plasma-sprayed and detonation gun coatings of Al2O3-13% TiO2 on biomedical alloy Ti-13Nb-13Zr and Gum metal2013In: ASTM Special Technical Publication, 2013, Vol. STP 1563, no January, p. 88-104Conference paper (Refereed)
    Abstract [en]

    The tribocorrosion behavior of titanium-based alloys is of significant interest as bio-implant materials. Bare alloys may not offer enough resistance to tribocorrosion, so coatings could be used to improve their performance. An important biomedical alloy, Ti-13Nb-13Zr, and a newly developed β titanium alloy called "Gum metal" (Ti-23%Ni-0.7%Ta-2%Zr-1 %O<inf>2</inf>) were used as substrates in the current work. Both were coated with conventional and nano-ceramic materials of Al<inf>2</inf>O<inf>3</inf>-TiO<inf>2</inf>. Bilayered coatings of ZrO<inf>2</inf>+Al<inf>2</inf>O<inf>3</inf>-13%TiO<inf>2</inf> were also applied to the Ti-13Nb-13Zr using plasma spray. The coatings on Ti-13Nb-13Zr were applied using plasma spray, whereas that on the Gum metal was applied by a detonation gun (D-Gun). Surface morphology was characterized using a scanning electron microscope (SEM). Tribocorrosion experiments were performed in salt water using a linear reciprocating ball-on-plate tribometer with an aluminum ball as the slider. The nano particles are embedded in the fully melted splats and offered better crack propagation resistance. The high velocity of the D-Gun process resulted in a higher volume fraction of the embedded nano particles and produced substantial improvement in wear resistance relative to the air-plasma-sprayed coating. The conventional coating, with its higher porosity, exhibited a high corrosion rate compared to nano coating. The D-Gun coating, with its lower porosity, had a higher corrosion resistance than the plasma-sprayed coating, but bilayered plasma-sprayed coating showed even higher corrosion resistance, owing to its dense microstructure. Open-circuit potential measurements before and during tribocorrosion showed that the bilayered plasma-sprayed coating had better tribocorrosion resistance than the other coatings. Electrochemical impedance spectroscopy indicated stable impedance values for the bilayered plasma-sprayed coating before and after tribocorrosion. Copyright © 2013 by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959.

  • 182.
    Ravi, N.
    et al.
    Hyderabad, India.
    Markandeya, R.
    Hyderabad, India.
    Joshi, Shrikant V.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing. Hyderabad, India.
    Effect of substrate roughness on adhesion and tribological properties of nc-TiAlN/a-Si3N4 nanocomposite coatings deposited by cathodic arc PVD process2017In: Surface Engineering, ISSN 0267-0844, E-ISSN 1743-2944, Vol. 33, no 1, p. 7-19Article in journal (Refereed)
    Abstract [en]

    TiN and Ti–Al–Si–N nanocomposite coatings of the type nc-TiAlN/a-Si3N4 have been prepared by cathodic arc physical vapour deposition process using cylindrical cathodes on high speed steel substrates with different surface roughness values, where the roughness is induced by emery paper method and diamond hand polishing. Fracture toughness studies by indentation method have shown that TiN is tougher than Ti–Al–Si–N nanocomposite coatings. Scratch and pin on disc wear tests have been conducted on the specimens to study the adhesion and tribological behaviour of these coatings respectiely. The wear mode between two mating surfaces is complex, and the wear behaviour can be understood better by studying the progression of surface changes and wear debris. The adhesion pattern of harder nanocomposite coating on smooth substrate surfaces is different from that of tougher TiN coating. Wear volume of these coatings decreases with substrate roughness, but it is found more for nanocomposite than for TiN.

  • 183.
    Ravi, N.
    et al.
    International Advanced Research Centre for Powder Metallurgy and New Materials, Balapur P.O., Hyderabad 500 005, India.
    Markandeya, R.
    Jawaharlal Nehru Technological University College of Engineering, Kukatpally, Hyderabad 500 085, India.
    Joshi, Shrikant V.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Fracture behaviour of nc-TiAlN/a-Si3N4 nanocomposite coating during nanoimpact test2017In: Surface Engineering, ISSN 0267-0844, E-ISSN 1743-2944, Vol. 33, no 4, p. 282-291Article in journal (Refereed)
    Abstract [en]

    Cyclic nanoimpact tests were carried on nc-TiAlN/a-Si3N4 nanocomposite, TiN and multilayered TiN/nanocomposite (NC) coatings to evaluate their resistance to fracture under cyclic impact loads. Fracture behaviour of the coatings was ascertained from fracture probability obtained from time-depth curves and focus ion beam milling images of resulting indentation impressions. TiN coating mainly showed intercolumnar cracks while the other coatings showed other modes of cracking, that is, lateral, inclined, bending, edge cracks, during testing. The performance ranking of the coatings, TiN &gt; TiN/NC &gt; nc-TiAlN/a-Si3N4, is linked to their β0 value, representing relative indentation depth of the coating-substrate composite hardness system at which the fractional hardness improvement equal to 50% of the maximum is retained and also their corresponding microstructure. Apart from enabling prediction of fracture resistance of the coatings, these studies provide useful insights into design and selection of coating materials for targeted machining applications. © 2016 Institute of Materials, Minerals and Mining

  • 184.
    Ravi, Nakula
    et al.
    International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI), Balapur PO, Hyderabad-500005, India.
    Markandeya, Ravvala
    Jawaharlal Nehru Technological Unversity College of Engineering, Kukatpally, Hyderabad-500085, India.
    Joshi, Shrikant. V.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing. Jawaharlal Nehru Technological Unversity College of Engineering, Kukatpally, Hyderabad-500085, India.
    Effect of nitrogen pressure on mechanical properties of nc-TiAlN/a-Si3N4 nanocomposite coatings deposited by cathodic arc PVD process2016In: Materials Today: Proceedings, E-ISSN 2214-7853, Vol. 3, no 9, p. 3002-3011Article in journal (Refereed)
    Abstract [en]

    The present work investigates effect of nitrogen pressure on composition and mechanical properties of superhard nc-TiAlN/a-Si3N4 nanocomposite coatings deposited by cathodic arc PVD process. As the nitrogen pressure increases, at.% ratio of (Al+Si)/Ti, initially, increases to a maximum and thereafter, it decreases while the nitrogen content follows the reverse trend. Hardness is influenced by chemical composition and crystallite size of TiAlN phase. Maximum average hardness of 37 GPa is achieved when at.% ratio of Al(+Si)/Ti or N/(Ti+Al+Si) approaches 1.0 and decrease in scratch adhesion strength is attributed to the defects caused by nitrogen deficiency.

  • 185. Ray, A. K.
    et al.
    Krishna, G.
    Swaminathan, J.
    Bose, S. C.
    Roy, N.
    Tiwari, Y. N.
    Roy, P. K.
    Alam, Z.
    Sharma, V. S. R. A.
    Joshi, S. V.
    Venkatraman, B.
    Das, D. K.
    Damage resistance of a thermal barrier coated superalloy used in aero turbine blade under accelerated creep condition2009In: High Temperature Materials and Processes, ISSN 0334-6455, E-ISSN 2191-0324, Vol. 28, no 1-2, p. 35-53Article in journal (Refereed)
    Abstract [en]

    This paper highlights the hot tensile and accelerated creep properties of a thermal barrier coated (TBC) AE 437A alloy used as a candidate blade material in aero engines. Acoustic emission technique has been utilised to characterise the ductile-brittle transition temperature of the bond coat. Results revealed that the DBTT (ductile to brittle transition temperature) of this bond coat is around 923 K, which is in close proximity to the value reported for NiCoCrAlY type of bond coat. Finite element technique used for analysing the equivalent stresses in the bond coat well within the elastic limit, revealed highest order of equivalent stress at 1073 K as the bond coat is ductile above 923 K. The lifetime of the TBC coated superai loy was superior to that of the bare substrate and that oxidation is likely the cause of the reduced life of the bare substrate as compared to the coated substrate while stress rupture or accelerated creep experiments are carried out in an oxidizing environment.. Delamination of the bond coat and that of the TBC at high stresses during accelerated creep was evident. During accelerated creep, the mode of fracture in the substrate at very high stresses was transgranular whereas that at low stresses was intergranular.

  • 186. Ray, A. K.
    et al.
    Roy, N.
    Kar, A.
    Bose, S. C.
    Das, G.
    Sahu, J. K.
    Das, D. K.
    Venkataraman, B.
    Joshi, S. V.
    Mechanical property and characterization of a NiCoCrAlY type metallic bond coat used in turbine blade2009In: Materials Science and Engineering A, Vol. 505, no 1-2, p. 96-104Article in journal (Refereed)
    Abstract [en]

    This paper highlights some of the results obtained while studying Ni20Co18Cr12.5Al0.6Y (NiCoCrAlY) type metallic bond-coat properties of a thermal-barrier coated (TBC), AE-437A Ni base superalloy mostly employed for manufacturing compressor and stationary stator blades in aero turbines. Experiments were mainly focused in the area of evaluation of microstructure, residual stress, shear strength, hardness and with special emphasis in establishing the ductile to brittle transition temperature (DBTT) of the bond coat by using acoustic emission technique during room temperature and high temperature tensile tests. Results reveal that the residual stress was tensile in nature in the TBC layer and compressive in the bond coat as well as in the substrate. The DBTT of this bond coat is around 650 °C, which is in close proximity to the value reported in literature for CoCrAlY type of bond coat. Finite element technique was used to analyze the equivalent stresses in the bond coat, the result of which revealed the highest order of equivalent stress 800 °C, as the bond coat is ductile above 650 °C. Shear strength of the bond coat is in close proximity with that of the bond strength reported in literature for CoCrAlY and Ni22Co17Cr12.5Al0.6Y types of bond coat. © 2009 Elsevier B.V. All rights reserved.

  • 187. Reddy, S. S.
    et al.
    Sundar, J. K. S.
    Venkataraman, B.
    Joshi, S. V.
    Evaluation of microstructural and dry sliding wear characteristics of pulsed Nd:YAG laser surface melted Al-Si alloys2004In: Proceedings of the International Conference on Advances in Surface Treatment: Research and Applications, ASTRA, 2004, p. 568-574Conference paper (Refereed)
    Abstract [en]

    Aluminium-Silicon alloys are being increasingly considered for manufacture of wear prone components in automobile and aircraft industries owing to their light weight, superior corrosion resistance and high thermal conductivity, besides their amenability to processing methods such as casting. However, poor tribological characteristics have hampered industrial adoption of the above class of alloys. In principle, the tribological properties of these alloys can be improved by refining the microstructure by laser remelting techniques. Recently, Nd:YAG lasers have been used for processing of reflective materials such as Aluminium, as these lasers have better absorptivity compared to the CO2 lasers. The present study investigates the microstructural characteristics and improvements in sliding wear resistance that can result from surface melting of Al-Si alloys using a 400 W pursed Nd:YAG laser. Three different Al-Si alloys with varying Si content 5%, 12.5% and 20% have been investigated in the present study. The microstructures of the transverse cross sections of the treated samples were examined in detail and X-ray diffraction (XRD) studies carried out to ascertain changes in phase constitution. The surface melting and subsequent rapid solidification was found to cause considerable refinement of the microstructure, which in turn increased the hardness in the treated layer compared with that of bulk. The effect of laser beam scan speed on microhardness of the treated samples was evaluated. Dry sliding wear tests were conducted on treated and untreated samples of Al-12Si using a pin-on disc tribometer. The volume wear rates determined in case of the treated and untreated samples are discussed in the paper. The results have also been correlated with the morphological and microstructural characteristics noted in the laser treated specimens. Copyright © 2004 by Society for Advancement of Heat Treatment & Surface Engineering (SAHTSE).

  • 188.
    Rossetti, Matteo
    et al.
    Dipartimento di Ingegneria “Enzo Ferrari”, Università di Modena e Reggio Emilia, Modena (ITA).
    Mathiyalagan, Sribalaji
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Björklund, Stefan
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Sowers, Sussane
    Hyperion Materials & Technologies, Worthington,Ohio (USA).
    Joshi, Shrikant V.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Advanced diamond-reinforced metal matrix composite (DMMC) coatings via HVAF process: Effect of particle size and nozzle characteristics on tribological properties2023In: Ceramics International, ISSN 0272-8842, E-ISSN 1873-3956, Vol. 49, no 11 Part A, p. 17838-17850Article in journal (Refereed)
    Abstract [en]

    High-velocity air fuel (HVAF) spraying is a versatile and cost-effective platform to fabricate wear resistant coatings. In this work, deposition of Nickel–Phosphorus cladded diamond feedstock is explored as a greener alternative to realize highly wear resistant large-area coatings. To the best of authors knowledge. this is the first study that has utilized HVAF technique for developing wear resistant Ni–P coatings reinforced with diamond (NCD). This work also aims to understand the effect of particle size by using coarse (20–30 μm) and fine NCD (10–15 μm) particles as feedstock. The importance of utilizing appropriate processing conditions was also highlighted by using two different nozzle configurations, for which the two powder particle sizes exhibited considerable differences in terms of microstructure, phase characteristics and mechanical properties. Further, the effect of annealing on the above coating characteristics was also examined, and it is shown that optimal spraying conditions can preclude the need for post-treatment. Furthermore, the as-deposited and annealed coatings were subjected to sliding wear tests to assess their tribological performance. Post-wear analysis performed on worn surfaces revealed the associated wear mechanisms. The results ensuing from this work lay the foundation for realizing new generation of HVAF sprayed wear resistant Ni–P/diamond composite coatings for diverse applications.

  • 189.
    Sadeghi, Esmaeil
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Joshi, Shrikant V.
    University West, Department of Engineering Science, Research Enviroment Production Technology West.
    Chlorine-induced high-temperature corrosion and erosion-corrosion of HVAF and HVOF-sprayed amorphous Fe-based coatings2019In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 371, no S1, p. 20-35Article in journal (Refereed)
    Abstract [en]

    Chlorine-induced high-temperature corrosion and erosion-corrosion behavior of amorphous Fe-based coatings sprayed by high velocity air-fuel (HVAF) and high velocity oxy-fuel (HVOF) techniques were investigated. The coated specimens were first exposed to isothermal high-temperature corrosion at 600 °C in ambient air with and without KCl. The exposed specimens were then subjected to alumina erodent. The as-sprayed HVAF coating showed a more compact and uniform microstructure with a higher hardness leading to higher corrosion and erosion-corrosion resistance. After erosion, all the coatings similarly exhibited a combined brittle/ductile damage to surface oxide scale that previously formed in the corrosive environment. The corrosion and erosion-corrosion behavior of the coatings primarily relied on the uniformity of coatings’ microstructure and distribution of alloying elements to form the protective oxide scale in the corrosive environment, which can resist against erodent in the erosive media. © 2019 Elsevier B.V.

  • 190.
    Sadeghi, Esmaeil
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Joshi, Shrikant V.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Advances in Corrosion-Resistant Thermal Spray Coatings for Renewable Energy Power Plants. Part I: Effect of Composition and Microstructure2019In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 28, no 8, p. 1749-1788Article in journal (Refereed)
    Abstract [en]

    Power generation from renewable resources has attracted increasing attention in recent years owing to the global implementation of clean energy policies. However, such power plants suffer from severe high-temperature corrosion of critical components such as water walls and superheater tubes. The corrosion is mainly triggered by aggressive gases like HCl, H2O, etc., often in combination with alkali and metal chlorides that are produced during fuel combustion. Employment of a dense defect-free adherent coating through thermal spray techniques is a promising approach to improving the performances of components as well as their lifetimes and, thus, significantly increasing the thermal/electrical efficiency of power plants. Notwithstanding the already widespread deployment of thermal spray coatings, a few intrinsic limitations, including the presence of pores and relatively weak intersplat bonding that lead to increased corrosion susceptibility, have restricted the benefits that can be derived from these coatings. Nonetheless, the field of thermal spraying has been continuously evolving, and concomitant advances have led to progressive improvements in coating quality; hence, a periodic critical assessment of our understanding of the efficacy of coatings in mitigating corrosion damage can be highly educative. The present paper seeks to comprehensively document the current state of the art, elaborating on the recent progress in thermal spray coatings for high-temperature corrosion applications, including the alloying effects, and the role of microstructural characteristics for understanding the behavior of corrosion-resistant coatings. In particular, this review comprises a substantive discussion on high-temperature corrosion mechanisms, novel coating compositions, and a succinct comparison of the corrosion-resistant coatings produced by diverse thermal spray techniques.

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  • 191.
    Sadeghi, Esmaeil
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Joshi, Shrikant V.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Advances in Corrosion-Resistant Thermal Spray Coatings for Renewable Energy Power Plants: Part II - Effect of Environment and Outlook2019In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 28, no 8, p. 1789-1850Article in journal (Refereed)
    Abstract [en]

    High-temperature corrosion of critical components such as water walls and superheater tubes in biomass/waste-fired boilers is a major challenge. A dense and defect-free thermal spray coating has been shown to be promising to achieve a high electrical/thermal efficiency in power plants. The field of thermal spraying and quality of coatings have been progressively evolving; therefore, a critical assessment of our understanding of the efficacy of coatings in increasingly aggressive operating environments of the power plants can be highly educative. The effects of composition and microstructure on high-temperature corrosion behavior of the coatings were discussed in the first part of the review. The present paper that is the second part of the review covers the emerging research field of performance assessment of thermal spray coatings in harsh corrosion-prone environments and provides a comprehensive overview of the underlying high-temperature corrosion mechanisms that lead to the damage of exposed coatings. The application of contemporary analytical methods for better understanding of the behavior of corrosion-resistant coatings is also discussed. A discussion based on an exhaustive review of the literature provides an unbiased commentary on the advanced accomplishments and some outstanding issues in the field that warrant further research. An assessment of the current status of the field, the gaps in the scientific understanding, and the research needs for the expansion of thermal spray coatings for high-temperature corrosion applications is also provided. © 2019, The Author(s).

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  • 192.
    Sadeghimeresht, Esmaeil
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Eklund, J.
    Chalmers University of Technology, Department of Environmental Inorganic Chemistry, Gothenburg, 412 96, Sweden.
    Phother Simon, J.
    Chalmers University of Technology, Department of Environmental Inorganic Chemistry, Gothenburg, 412 96, Sweden.
    Lyske, J.
    Chalmers University of Technology, Department of Environmental Inorganic Chemistry, Gothenburg, 412 96, Sweden.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Joshi, Shrikant V.
    University West, Department of Engineering Science, Research Enviroment Production Technology West.
    Oxidation behaviour of HVAF-sprayed NiCr coating in moisture-laden environment2017In: Proceedings of the International Thermal Spray Conference & Exposition (ITSC 2017), New York: Curran Associates, Inc. , 2017, Vol. 2, p. 644-646Conference paper (Refereed)
    Abstract [en]

    Reducing CO2 emissions from power generation plants is intimately related to enhancing their thermal efficiency, which can be achieved by increasing the temperature/pressure of steam. However, any increase in steam temperature is inevitably accompanied by accelerated oxidation of boiler components. The use of renewable fuels such as biomass increases the problem by introducing a number of corrosive compounds into the boiler environment, resulting in more rapid degradation of components. Although thermal sprayed coatings are techno-commercially attractive solutions for augmenting the durability of degradation-prone boiler components and are already used, further improvements in their performance are continuously sought. High-velocity air fuel (HVAF) coatings are promising in this context. In the present work, isothermal oxidation behavior of a candidate HVAF-sprayed Ni21Cr was studied in N2 + 5% O2 + 20% H2O at 600°C for 168h. The oxide scale growth mechanisms were studied by BIB/SEM/EDX to evaluate the effectiveness of the coatings. It was found that the water vapor effect is insignificant due to the Cr reservoir in the Ni21Cr coating, which yielded enhanced oxidation protection by forming nano-scale Cr2O3

  • 193.
    Sadeghimeresht, Esmaeil
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Eklund, Johan
    University of Chalmers, Gothenburg, Sweden.
    Phother Simon, Julien
    University of Chalmers, Gothenburg, Sweden.
    Liske, Jesper
    University of Chalmers, Gothenburg, Sweden.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Joshi, Shrikant V.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    HVAF spraying for biomass boiler applications:: Oxidation behavior of Ni-based coatings in moisture-laden environment2017Conference paper (Other academic)
  • 194.
    Sadeghimeresht, Esmaeil
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Eklund, Johan
    Chalmers University of Technology, Department of Environmental Inorganic Chemistry, 41296 Gothenburg, Sweden.
    Simon, Julien Phother
    Chalmers University of Technology, Department of Environmental Inorganic Chemistry, 41296 Gothenburg, Sweden.
    Liske, Jesper
    Chalmers University of Technology, Department of Environmental Inorganic Chemistry, 41296 Gothenburg, Sweden.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Joshi, Shrikant V.
    University West, Department of Engineering Science, Research Enviroment Production Technology West.
    Effect of water vapor on the oxidation behavior of HVAF-sprayed NiCr and NiCrAlY coatings2018In: Materials and corrosion - Werkstoffe und Korrosion, ISSN 0947-5117, E-ISSN 1521-4176, Vol. 69, no 10, p. 1431-1440Article in journal (Refereed)
    Abstract [en]

    Isothermal oxidation behavior of NiCr and NiCrAlY coatings deposited onto low alloy 16Mo3 steel by high-velocity air fuel (HVAF) process was investigated in 5% O-2+20% H2O+N-2 at 600 degrees C for 168h. Whereas NiCrAlY showed lower mass gain compared to NiCr, both coatings succeeded in maintaining the integrity with the substrate during the exposure without any breakaway oxidation. A thin Cr-rich oxide scale (Cr2O3) formed on NiCr, and a thin mixed oxide scale (Al2O3 with NiCr2O4) formed on NiCrAlY significantly increasing the oxidation protection in the presence of water vapor.

  • 195.
    Sadeghimeresht, Esmaeil
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Hooshyar, H.
    Department of Environmental Inorganic Chemistry, Chalmers University of Technology, Gothenburg, Sweden.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Joshi, Shrikant V.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Nylén, Per
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Oxidation Behavior of HVAF-Sprayed NiCoCrAlY Coating in H2–H2O Environment2016In: Oxidation of Metals, ISSN 0030-770X, E-ISSN 1573-4889, Vol. 86, no 3-4, p. 299-314Article in journal (Refereed)
    Abstract [en]

    Isothermal oxidation behavior of an HVAF-sprayed NiCoCrAlY coating on AISI 304L was studied in an Ar–10 %H2–20 %H2O environment at 600 °C. Techniques such as BIB/SEM, EDS, and XRD were used to comprehensively characterize the coating and the coating/substrate interface to investigate the oxidation mechanisms. Results were also compared with those obtained from an uncoated AISI 304L substrate. The alumina-forming NiCoCrAlY coating was found to exhibit superior oxidation behavior due to the formation of a slow-growing and protective Al2O3 scale, while the chromia-forming bare 304L substrate lost its protective capability due to the formation of a duplex [Fe3O4 on (Fe,Cr)3O4 spinel oxide] corrosion product layer.

  • 196.
    Sadeghimeresht, Esmaeil
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Jafari, Reza
    Dep. of Material Science and Engineering, Tarbiat Modares University, Tehran, Iran .
    Shahrabi Farahani, Taghi
    Dep. of Material Science and Engineering, Tarbiat Modares University, Tehran, Iran .
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Joshi, Shrikant V.
    University West, Department of Engineering Science, Research Enviroment Production Technology West.
    High Temperature Corrosion of HVAF-Sprayed NiCrAlY Coating Exposed to Various Corrosive Environments2017Conference paper (Other academic)
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  • 197.
    Sadeghimeresht, Esmaeil
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Karimi Neghlani, Paria
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Zhang, Pimin
    Linköping University,Department of Management and Engineering, Linköping, Sweden.
    Peng, Ru
    Linköping University,Department of Management and Engineering, Linköping, Sweden.
    Andersson, Joel
    University West, Department of Engineering Science, Division of Welding Technology.
    Pejryd, Lars
    Örebro University, School of Science and Technology, Örebro, Sweden.
    Joshi, Shrikant V.
    University West, Department of Engineering Science, Research Enviroment Production Technology West.
    Isothermal Oxidation Behavior of EBM-Additive Manufactured Alloy 7182018In: Proceedings of the 9th International Symposium on Superalloy 718 & Derivatives: Energy, Aerospace, and Industrial Applications / [ed] Ott, E., Liu, X., Andersson, J., Bi, Z., Bockenstedt, K., Dempster, I., Groh, J., Heck, K., Jablonski, P., Kaplan, M., Nagahama, D. and Sudbrack, C., Springer, 2018, p. 219-240Conference paper (Refereed)
    Abstract [en]

    Oxidation of Alloy 718 manufactured by electron beam melting (EBM) process has been undertaken in ambient air at 650, 700, and 800 °C for up to 168 h. At 800 °C, a continuous external chromia oxide enriched in (Cr, Ti, Mn, Ni) and an internal oxide that was branched structure of alumina formed, whereas at 650 and 700 °C, a continuous, thin and protective chromia layer was detected. The oxidation kinetics of the exposed EBM Alloy 718 followed the parabolic rate law with an effective activation energy of ~248 ± 22 kJ/mol in good agreement with values in the literature for conventionally processed chromia-forming Ni-based superalloys. The oxide scale formed on the surface perpendicular to the build direction was slightly thicker, and more adherent compared to the scale formed on the surface along the build direction, attributed to the varied grain texture in the two directions of the EBM-manufactured specimens. The increased oxygen diffusion and high Cr depletion found on the surface along the build direction were attributed to the fine grains and formation of vacancies/voids along this grain orientation.

  • 198.
    Sadeghimeresht, Esmaeil
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Huhtakangas, M.b
    M. H. Engineering AB, 691 42 Karlskoga, Sweden.
    Joshi, Shrikant V.
    University West, Department of Engineering Science, Research Enviroment Production Technology West.
    Isothermal oxidation of HVAF-sprayed Ni-based chromia, alumina and mixed-oxide scale forming coatings in ambient air2017In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 316, p. 10-21Article in journal (Refereed)
    Abstract [en]

    The power generation industry has been progressively shifting towards higher operating steam temperatures and pressures to increase efficiency and reduce CO2 emissions. However, higher operating temperatures lead to more aggressive oxidation of the boiler components. A promising route to improve the durability of degradation-prone components is through deployment of high-performance coatings. In the present work, four Ni-based coatings - Ni21Cr, Ni5Al, Ni21Cr9Mo, and Ni21Cr7Al1Y - thermally sprayed by the high-velocity air fuel (HVAF) technique on boiler steel (16Mo3) substrates were investigated. The isothermal oxidation behavior of the coatings was studied in ambient air environment at 600 °C for different time intervals i.e. 1, 5, 10, 24, 48, 96, and 168 h. The oxidation behavior of the as-sprayed and polished coatings was compared. The protective α-Al2O3 was not detected on the exposed alumina-forming NiAl coating. On the other hand, Cr2O3 along with a small amount of NiO were the main oxidation products on the surface of the NiCr and NiCrMo coatings, and were found to be relatively less protective. The mixed-oxide scale forming NiCrAlY coatings showed the best oxidation resistance due to the formation of a thin and slow-growing Al2O3 scale along with Ni(Al,Cr)2O4 and Cr2O3. The polished coatings were found to significantly reduce the oxidation rate in each case as the protective scale-forming elements were more uniformly supplied to the surface oxide scale by removing the surface asperities. © 2017 Elsevier B.V.

  • 199.
    Sadeghimeresht, Esmaeil
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Hussain, Tanvir
    Univ Nottingham, Fac Engn, Nottingham NG7 2RD, England.
    Huhtakangas, Matti
    MH Engn AB, S-69142 Karlskoga, Sweden.
    Joshi, Shrikant V.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Effect of SiO2 Dispersion on Chlorine-Induced High-Temperature Corrosion of High-Velocity Air-Fuel Sprayed NiCrMo Coating2018In: Corrosion, ISSN 0010-9312, E-ISSN 1938-159X, Vol. 74, no 9, p. 984-1000Article in journal (Refereed)
    Abstract [en]

    NiCrMo coatings with and without dispersed SiO2 were deposited using high-velocity air-fuel technique. Thermogravimetric experiments were conducted in 5% O-2 + 500 vppm HCl + N-2 with and without a KCl deposit at 600 degrees C for up to 168 h. The SiO2-containing coating showed lower weight change as a result of formation of a protective and adherent Cr-rich oxide scale. SiO2 decelerated short-circuit diffusion of Cr3+ through scale's defects, e.g., vacancies, and promoted the selective oxidation of Cr to form the protective Cr-rich oxide scale. Furthermore, the presence of SiO2 led to less subsurface depletion of Cr in the coating, and accordingly less corrosion of the substrate. The formed corrosion product on the SiO2-free coating was highly porous, non-adherent, and thick.

  • 200.
    Sadeghimeresht, Esmaeil
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Production Engineering. University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Joshi, Shrikant V.
    University West, Department of Engineering Science, Research Enviroment Production Technology West. University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Isothermal oxidation behavior of HVAF-sprayed Ni and NiCr coatings in H2-H2O environment2017In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 317, p. 17-25Article in journal (Refereed)
    Abstract [en]

    The formation of a protective chromia scale on stainless steels is known to be suppressed by the presence of water vapor in reducing conditions. Thermal spray coatings present a promising approach to improve the durability of steels by transferring the first line of oxidation attack from the bulk steel to the coating. In the present work, isothermal oxidation behavior of Ni and NiCr coatings deposited by High-Velocity Air Fuel (HVAF) process on 304L stainless steel was investigated at 600 degrees C for 168 h. Ar-10%H-2-20%H2O was selected as the oxidation environment to study the oxidation behavior of the coatings in a low pO(2) environment containing H2 and H2O. BIB/ SEM, EDS, and XRD techniques were used to characterize the as-sprayed coatings and to investigate the oxidation mechanisms in the coated samples. Results showed that both Ni and NiCr coatings imparted oxidation protection to the 304L substrate. The chromia-forming 304L steel presented a duplex but non-protective oxide scale comprising of an outer Fe3O4 layer on an inner (Fe, Cr)(3)O-4-spinel oxide. In contrast, the NiCr coating presented superior oxidation behavior due to the formation of a continuous, thin, and slow-growing Cr2O3 scale. The Ni coating, too, protected the substrate owing to limited nucleation and growth of the deleterious NiO scale in the low-oxygen -activity environment. (C) 2017 Elsevier B.V. All rights reserved.

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