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Ganvir, A., Björklund, S., Yao, Y., Vadali, S. V., Klement, U. & Joshi, S. V. (2019). A facile approach to deposit graphenaceous composite coatings by suspension plasma spraying. Coatings, 9(3), Article ID 171.
Open this publication in new window or tab >>A facile approach to deposit graphenaceous composite coatings by suspension plasma spraying
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2019 (English)In: Coatings, ISSN 2079-6412, Vol. 9, no 3, article id 171Article in journal (Refereed) Published
Abstract [en]

This paper demonstrates, for the first time ever, the deposition of graphenaceous composite coatings using an easy, yet robust, suspension plasma spraying (SPS) process. As a case study, a composite coating comprising 8 wt.% of yttria-stabilized-zirconia (8YSZ) and reinforced with graphene oxide (GO) was deposited on a steel substrate. The coatings were sprayed using an 8YSZ-GO mixed suspension with varied plasma spray parameters. Establishing the possibility of retaining the graphene in a ceramic matrix using SPS was of specific interest. Electron microscopy and Raman spectroscopy confirmed the presence of graphenaceous material distributed throughout the coating in the 8YSZ matrix. The experimental results discussed in this work confirm that SPS is an immensely attractive pathway to incorporate a graphenaceous material into virtually any matrix material and can potentially have major implications in enabling the deposition of large-area graphene-containing coatings for diverse functional applications. © 2019 by the authors.

Place, publisher, year, edition, pages
MDPI AG, 2019
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-13737 (URN)10.3390/coatings9030171 (DOI)000465608700002 ()2-s2.0-85062495390 (Scopus ID)
Available from: 2019-03-21 Created: 2019-03-21 Last updated: 2019-05-10
Sadeghi, E. & Joshi, S. V. (2019). Chlorine-induced high-temperature corrosion and erosion-corrosion of HVAF and HVOF-sprayed amorphous Fe-based coatings. Surface & Coatings Technology, 371(S1), 20-35
Open this publication in new window or tab >>Chlorine-induced high-temperature corrosion and erosion-corrosion of HVAF and HVOF-sprayed amorphous Fe-based coatings
2019 (English)In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 371, no S1, p. 20-35Article in journal (Refereed) Published
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.

Keywords
Air, Alloying elements, Alumina, Aluminum oxide, Chlorine, Corrosion resistance, Corrosive effects, Erosion, Fuels, High temperature corrosion, HVOF thermal spraying, Microstructure, Potassium compounds, Scale (deposits), Sprayed coatings, Thermal spraying, Amorphous coating, Chlorine-induced high-temperature corrosion, Erosion - corrosions, HVAF, HVOF, Corrosion resistant coatings
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-13514 (URN)10.1016/j.surfcoat.2019.01.080 (DOI)000472694300004 ()2-s2.0-85060532855 (Scopus ID)
Funder
Knowledge Foundation, RUN 20160201Region Västra Götaland, 2016-01489
Available from: 2019-03-21 Created: 2019-03-21 Last updated: 2019-10-16Bibliographically approved
Aranke, O., Algenaid, W., Awe, S. & Joshi, S. V. (2019). Coatings for automotive gray cast iron brake discs: A review. Coatings, 9(9), Article ID 552.
Open this publication in new window or tab >>Coatings for automotive gray cast iron brake discs: A review
2019 (English)In: Coatings, ISSN 2079-6412, Vol. 9, no 9, article id 552Article in journal (Refereed) Published
Abstract [en]

Gray cast iron (GCI) is a popular automotive brake disc material by virtue of its high melting point as well as excellent heat storage and damping capability. GCI is also attractive because of its good castability and machinability, combined with its cost-effectiveness. Although several lightweight alloys have been explored as alternatives in an attempt to achieve weight reduction, their widespread use has been limited by low melting point and high inherent costs. Therefore, GCI is still the preferred material for brake discs due to its robust performance. However, poor corrosion resistance and excessive wear of brake disc material during service continue to be areas of concern, with the latter leading to brake emissions in the form of dust and particulate matter that have adverse effects on human health. With the exhaust emission norms becoming increasingly stringent, it is important to address the problem of brake disc wear without compromising the braking performance of the material. Surface treatment of GCI brake discs in the form of a suitable coating represents a promising solution to this problem. This paper reviews the different coating technologies and materials that have been traditionally used and examines the prospects of some emergent thermal spray technologies, along with the industrial implications of adopting them for brake disc applications. © 2019 by the authors.

National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear) Vehicle Engineering
Identifiers
urn:nbn:se:hv:diva-14488 (URN)10.3390/coatings9090552 (DOI)000487973600064 ()2-s2.0-85072179966 (Scopus ID)
Funder
Swedish Energy Agency, 46393-1
Available from: 2019-10-01 Created: 2019-10-01 Last updated: 2019-10-15
Mahade, S., Curry, N., Björklund, S., Markocsan, N. & Joshi, S. V. (2019). Durability of Gadolinium Zirconate/YSZ Double-Layered Thermal Barrier Coatings under Different Thermal Cyclic Test Conditions. Materials, 12(14), Article ID E2238.
Open this publication in new window or tab >>Durability of Gadolinium Zirconate/YSZ Double-Layered Thermal Barrier Coatings under Different Thermal Cyclic Test Conditions
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2019 (English)In: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 12, no 14, article id E2238Article in journal (Refereed) Published
Abstract [en]

Higher durability in thermal barrier coatings (TBCs) is constantly sought to enhance the service life of gas turbine engine components such as blades and vanes. In this study, three double layered gadolinium zirconate (GZ)-on-yttria stabilized zirconia (YSZ) TBC variants with varying individual layer thickness but identical total thickness produced by suspension plasma spray (SPS) process were evaluated. The objective was to investigate the role of YSZ layer thickness on the durability of GZ/YSZ double-layered TBCs under different thermal cyclic test conditions i.e., thermal cyclic fatigue (TCF) at 1100 °C and a burner rig test (BRT) at a surface temperature of 1400 °C, respectively. Microstructural characterization was performed using SEM (Scanning Electron Microscopy) and porosity content was measured using image analysis technique. Results reveal that the durability of double-layered TBCs decreased with YSZ thickness under both TCF and BRT test conditions. The TBCs were analyzed by SEM to investigate microstructural evolution as well as failure modes during TCF and BRT test conditions. It was observed that the failure modes varied with test conditions, with all the three double-layered TBC variants showing failure in the TGO (thermally grown oxide) during the TCF test and in the ceramic GZ top coat close to the GZ/YSZ interface during BRT. Furthermore, porosity analysis of the as-sprayed and TCF failed TBCs revealed differences in sintering behavior for GZ and YSZ. The findings from this work provide new insights into the mechanisms responsible for failure of SPS processed double-layered TBCs under different thermal cyclic test conditions.

Keywords
burner rig test, double-layered TBC, gadolinium zirconate, suspension plasma spray, thermal cyclic fatigue, yttria stabilized zirconia
National Category
Manufacturing, Surface and Joining Technology
Identifiers
urn:nbn:se:hv:diva-14438 (URN)10.3390/ma12142238 (DOI)000480454300026 ()31336713 (PubMedID)2-s2.0-85070469165 (Scopus ID)
Funder
Knowledge Foundation, Dnr-20140130
Available from: 2019-10-02 Created: 2019-10-02 Last updated: 2019-10-15
Goel, S., Ahlfors, M., Bahbou, F. & Joshi, S. V. (2019). Effect of Different Post-treatments on the Microstructure of EBM-Built Alloy 718. Journal of materials engineering and performance (Print), 28(2), 673-680
Open this publication in new window or tab >>Effect of Different Post-treatments on the Microstructure of EBM-Built Alloy 718
2019 (English)In: Journal of materials engineering and performance (Print), ISSN 1059-9495, E-ISSN 1544-1024, Vol. 28, no 2, p. 673-680Article in journal (Refereed) Published
Abstract [en]

Electron beam melting (EBM) of Alloy 718 is of rapidly growing interest as it allows cost-effective production of complex components. However, the inherent flaws in the component in as-built state are of concern in view of the severe working conditions in which Alloy 718 components typically operate. The present work entails an investigation of changes in microstructure that accompany some post-treatments that are being widely considered to address defects in EBM processed Alloy 718. The effect of two different post-treatments, namely hot isostatic pressing (HIP) and a combined HIP + heat treatment (HT) carried out inside the HIP vessel, have been studied and results from as-built and post-treated specimens were compared in terms of porosity/lack-of-fusion, microstructure, phase constitution (NbC content, ÎŽ-phase) and micro-hardness. Post-treatment resulted in reduction in defect content by more than an order of magnitude. HIPing led to complete dissolution of ÎŽ phase. In comparison to as-built material, HIPed specimens exhibited significant drop in hardness. However, a sharp ‘recovery’ of hardness to yield values higher than in as-built condition was observed after HIP + HT and can be attributed to precipitation of γ′′ phase. © 2018, The Author(s).

Keywords
3D printers, Cost effectiveness, Defects, Electron beam melting, Electron beams, Hardness, Heat treatment, Hot isostatic pressing, Microhardness, Microstructure, Alloy 718, Complete dissolution, Complex components, Cost-effective production, Defect contents, Phase constitution, Post treatment, Yield value, Niobium compounds
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-13133 (URN)10.1007/s11665-018-3712-0 (DOI)000458782100012 ()2-s2.0-85055983075 (Scopus ID)
Funder
Knowledge Foundation, 20160281
Note

First Online: 29 October 2018

Available from: 2018-11-19 Created: 2018-11-19 Last updated: 2019-06-12Bibliographically approved
Goel, S., Sittiho, A., Charit, I., Klement, U. & Joshi, S. V. (2019). Effect of post-treatments under hot isostatic pressure on microstructural characteristics of EBM-built Alloy 718. Additive Manufacturing, 28, 727-737
Open this publication in new window or tab >>Effect of post-treatments under hot isostatic pressure on microstructural characteristics of EBM-built Alloy 718
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2019 (English)In: Additive Manufacturing, ISSN 2214-8604, Vol. 28, p. 727-737Article in journal (Refereed) Published
Abstract [en]

Electron beam melting (EBM) has emerged as an important additive manufacturing technique. In this study, Alloy 718 produced by EBM was investigated in as-built and post-treated conditions for microstructural characteristics and hardness. The post-treatments investigated were hot isostatic pressing (HIP) and combined HIP + heat treatment (HIP + HT) carried out as a single cycle inside the HIP vessel. Both the post-treatments resulted in significant decrease in defects inevitably present in the as-built material. The columnar grain structure of the as-built material was found to be maintained after post-treatment, with some sporadic localized grain coarsening noted. Although HIP led to complete dissolution of δ and γ′′ phase, stable NbC and TiN (occasionally present) particles were observed in the post-treated specimens. Significant precipitation of γ′′ phase was observed after HIP + HT, which was attributed to the two-step aging heat treatment carried out during HIP + HT. The presence of γ′′ phase or otherwise was correlated to the hardness of the material. While the HIP treatment resulted in drop in hardness, HIP + HT led to 'recovery' of the hardness to values exceeding those exhibited by the as-built material. © 2019 Elsevier B.V.

Keywords
3D printers; Additives; Coarsening; Electron beam melting; Electron beams; Hardness; Heat treatment; Hot isostatic pressing; Sintering; Titanium nitride, Alloy 718; Columnar grain structure; Complete dissolution; Grain coarsening; Hot isostatic pressure; Manufacturing techniques; Micro-structural characteristics; Post treatment, Niobium compounds
National Category
Manufacturing, Surface and Joining Technology Metallurgy and Metallic Materials
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-14457 (URN)10.1016/j.addma.2019.06.002 (DOI)2-s2.0-85067846675 (Scopus ID)
Funder
Knowledge Foundation, 20160281
Available from: 2019-10-02 Created: 2019-10-02 Last updated: 2019-10-03
Zhang, P., Sadeghi, E., Chen, S., Li, X.-H., Markocsan, N., Joshi, S. V., . . . Peng, R. L. n. (2019). Effects of surface finish on the initial oxidation of HVAF-sprayed NiCoCrAlY coatings. Surface & Coatings Technology, 364, 43-56
Open this publication in new window or tab >>Effects of surface finish on the initial oxidation of HVAF-sprayed NiCoCrAlY coatings
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2019 (English)In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 364, p. 43-56Article in journal (Refereed) Published
Abstract [en]

Oxide scale formed on HVAF-sprayed NiCoCrAlY coatings and the effect of surface treatment were investigated by a multi-approach study combining photo-stimulated luminescence, microstructural observation and mass gain. The initial oxidationbehaviour of as-sprayed, polished and shot-peened coatings at 1000 °C is studied. Both polished and shot-peened coatings exhibited superior performance due to rapid formation of α-Al2O3 fully covering the coating and suppressing the growth of transient alumina, assisted by a high density of α-Al2O3 nuclei on surface treatment induced defects. Moreover, the fast development of a two-layer alumina scale consisting of an inward-grown inner α-Al2O3 layer and an outer layer transformed from outward-grown transient alumina resulted in a higher oxide growth rate of the as-sprayed coating.

Keywords
Oxidation, Transient to alpha transformation, Surface treatment, Polishing, Shot-peening, Photo-stimulated luminescence spectroscopy
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-13736 (URN)10.1016/j.surfcoat.2019.02.068 (DOI)000463302800006 ()2-s2.0-85062231529 (Scopus ID)
Funder
Swedish Energy Agency, KME-703
Available from: 2019-03-21 Created: 2019-03-21 Last updated: 2019-07-01Bibliographically approved
Ganvir, A., Calinas, R. F., Markocsan, N., Curry, N. & Joshi, S. V. (2019). Experimental visualization of microstructure evolution during suspension plasma spraying of thermal barrier coatings. Journal of the European Ceramic Society, 39(2-3), 470-481
Open this publication in new window or tab >>Experimental visualization of microstructure evolution during suspension plasma spraying of thermal barrier coatings
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2019 (English)In: Journal of the European Ceramic Society, ISSN 0955-2219, E-ISSN 1873-619X, Vol. 39, no 2-3, p. 470-481Article in journal (Refereed) Published
Abstract [en]

This paper investigates the evolution of microstructure of thermal barrier coatings (TBCs) produced by suspension plasma spraying (SPS) through a careful experimental study. Understanding the influence of different suspension characteristics such as type of solvent, solid load content and median particle size on the ensuing TBC microstructure, as well as visualizing the early stages of coating build-up leading to formation of a columnar microstructure or otherwise, was of specific interest. Several SPS TBCs with different suspensions were deposited under identical conditions (same substrate, bond coat and plasma spray parameters). The experimental study clearly revealed the important role of suspension characteristics, namely surface tension, density and viscosity, on the final microstructure, with study of its progressive evolution providing invaluable insights. Variations in suspension properties manifest in the form of differences in droplet momentum and trajectory, which are found to be key determinants governing the resulting microstructure (e.g., lamellar/vertically cracked or columnar).

Keywords
Suspension plasma spraying, Thermal barrier coatings, Droplet momentum, Columnar microstructure, Microstructure evolution
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering; Production Technology
Identifiers
urn:nbn:se:hv:diva-12948 (URN)10.1016/j.jeurceramsoc.2018.09.023 (DOI)000450379400042 ()2-s2.0-85053889817 (Scopus ID)
Funder
Region Västra Götaland, RUN 612-0974-13
Available from: 2018-10-26 Created: 2018-10-26 Last updated: 2018-12-20Bibliographically approved
Mahade, S., Narayan, K., Govindarajan, S., Björklund, S., Curry, N. & Joshi, S. V. (2019). Exploiting Suspension Plasma Spraying to Deposit Wear-Resistant Carbide Coatings.. Materials, 12(15), Article ID E2344.
Open this publication in new window or tab >>Exploiting Suspension Plasma Spraying to Deposit Wear-Resistant Carbide Coatings.
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2019 (English)In: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 12, no 15, article id E2344Article in journal (Refereed) Published
Abstract [en]

Titanium- and chromium-based carbides are attractive coating materials to impart wear resistance. Suspension plasma spraying (SPS) is a relatively new thermal spray process which has shown a facile ability to use sub-micron and nano-sized feedstock to deposit high-performance coatings. The specific novelty of this work lies in the processing of fine-sized titanium and chromium carbides (TiC and Cr3C2) in the form of aqueous suspensions to fabricate wear-resistant coatings by SPS. The resulting coatings were characterized by surface morphology, microstructure, phase constitution, and micro-hardness. The abrasive, erosive, and sliding wear performance of the SPS-processed TiC and Cr3C2 coatings was also evaluated. The results amply demonstrate that SPS is a promising route to manufacture superior wear-resistant carbide-based coatings with minimal in situ oxidation during their processing.

Keywords
chromium carbide, suspension plasma spray, titanium carbide, wear
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-14437 (URN)10.3390/ma12152344 (DOI)000482576900005 ()31344804 (PubMedID)2-s2.0-85070407089 (Scopus ID)
Available from: 2019-10-02 Created: 2019-10-02 Last updated: 2019-10-15
Eklund, J., Phother, J., Sadeghi, E., Joshi, S. V. & Liske, J. (2019). High-Temperature Corrosion of HVAF-Sprayed Ni-Based Coatings for Boiler Applications. Oxidation of Metals, 91(5-6), 729-747
Open this publication in new window or tab >>High-Temperature Corrosion of HVAF-Sprayed Ni-Based Coatings for Boiler Applications
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2019 (English)In: Oxidation of Metals, ISSN 0030-770X, E-ISSN 1573-4889, Vol. 91, no 5-6, p. 729-747Article in journal (Refereed) Published
Abstract [en]

The present study investigates the initial corrosion behaviour of HVAF-sprayed NiCr, NiAl and NiCrAlY coatings in two different environments, O 2 + H 2 O and O 2 + H 2 O + KCl at 600 °C for up to 168 h in order to evaluate the possibility of utilizing such coatings in biomass- and waste-fired boilers. SEM/EDX analysis showed that all coatings displayed a protective behaviour in O 2 + H 2 O. Upon addition of KCl (O 2 + H 2 O + KCl), the corrosion behaviour of the NiCr coating drastically changed as it formed a thick oxide layer and displayed major chlorine diffusion down to the substrate. The NiCrAlY coating displayed a significantly better corrosion resistance with only minor oxide formation. The NiAl coating exhibited a protective behaviour similar to when exposed in the absence of KCl indicating that a thin protective oxide has formed on the coating surface. The performance of the NiAl and NiCrAlY coatings is promising for future studies with long-term exposures in more corrosive environments such as in a biomass- and waste-fired boiler. © 2019, The Author(s).

Keywords
Aluminum alloys; Aluminum corrosion; Binary alloys; Biomass; Boiler corrosion; Boilers; Chlorine compounds; Chromium alloys; Corrosion resistance; Corrosion resistant coatings; Corrosive effects; Diffusion coatings; High temperature applications; High temperature corrosion; Sprayed coatings; Wastes, Corrosion behaviour; Corrosive environment; HVAF; Long term exposure; Ni-based coatings; NiCrAlY coating; Protective oxides; Waste-fired boilers, Potassium compounds
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-13758 (URN)10.1007/s11085-019-09906-0 (DOI)000467574600011 ()2-s2.0-85062942037 (Scopus ID)
Funder
Knowledge Foundation, RUN 2016-0201Region Västra Götaland, RUN 2016-01489
Available from: 2019-05-17 Created: 2019-05-17 Last updated: 2019-06-05
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0001-5521-6894

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