Change search
Link to record
Permanent link

Direct link
BETA
Publications (10 of 36) Show all publications
Dahat, S., Hurtig, K., Andersson, J. & Scotti, A. (2020). A Methodology to Parameterize Wire + Arc Additive Manufacturing: A Case Study for Wall Quality Analysis. Journal of Manufacturing and Materials Processing, 4(1), Article ID 14.
Open this publication in new window or tab >>A Methodology to Parameterize Wire + Arc Additive Manufacturing: A Case Study for Wall Quality Analysis
2020 (English)In: Journal of Manufacturing and Materials Processing, Vol. 4, no 1, article id 14Article in journal (Refereed) Published
Abstract [en]

The objective of this work was the development of a methodology to parametrize wire + arc additive manufacturing (WAAM), aiming dimension repeatability, and tolerances. Parametrization of WAAM is a difficult task, because multiple parameters are involved and parameters are inter-dependent on each other, making overall process complex. An approach to study WAAM would be through operational maps. The choice of current (Im) and travel speed (TS) for the desirable layer width (LW) determines a parametrization that leads to either more material or less material to be removed in post-operations, which is case study chosen for this work. The work development had four stages. First stage, named ‘mock design’, had the objective of visualizing the expected map and reduce further number of experiments. At the second stage, ‘pre-requisite for realistic operational map’, the objective was to determine the operating limits of TS and Im with the chosen consumables and equipment. Within the ‘realistic operational map’ stage, a design for the experiments was applied to cover a parametric area (working envelope) already defined in the previous stage and long and tall walls were additively manufactured. Actual values of LW (external and effective layer width) were measured and an actual operating envelope was reached. According to the geometry-oriented case study, a surface waviness index (SWindex) was defined, determined, and overlapped in the envelope. It was observed that the walls with parameters near the travel speed limits presented higher SWindex. This operational map was further validated (fourth stage) by selecting a target LW and finding corresponding three parametric set (covering the whole range of operational map) to produce walls on which geometry characterization was carried out. After geometry characterization, obtained LW was compared with the target LW (the maximum values were very tied, with deviations from +0.3 to 0.5 mm), with a SWindex deviation at the order of 0.05. Both results evidence high reproductivity of the process, validating the proposed methodology to parametrize WAAM.

Keywords
CMT, GMAW, operational map, parameterization, printing quality, WAAM
National Category
Manufacturing, Surface and Joining Technology
Identifiers
urn:nbn:se:hv:diva-15013 (URN)10.3390/jmmp4010014 (DOI)
Funder
Knowledge Foundation
Available from: 2020-02-24 Created: 2020-02-24 Last updated: 2020-02-24
Hosseini, V., Hurtig, K. & Karlsson, L. (2020). Bead by bead study of a multipass shielded metal arc-welded super-duplex stainless steel. Welding in the World
Open this publication in new window or tab >>Bead by bead study of a multipass shielded metal arc-welded super-duplex stainless steel
2020 (English)In: Welding in the World, ISSN 0043-2288, E-ISSN 1878-6669Article in journal (Refereed) Epub ahead of print
Abstract [en]

The present study aims at investigating bead geometry and the evolution of microstructure with thermal cycles in multipass shielded metal arc welding of a V-groove 13-mm type-2507 super-duplex stainless steel (SDSS) plate. The weld consisted of 4 beads produced with arc energies of 0.81-1.06 kJ/mm. The upper beads showed lower base metal (BM) dilution than the first bead. Thermal cycles were recorded with thermocouples, indicating that the cooling rate decreased in the as-deposited weld zone when adding a new bead. Ferrite fraction in the as-welded condition was lower for the upper beads. The austenite grain morphology in reheated passes varied depending on the local peak temperatures and the number of reheating passes. Sigma phase precipitated in a location reheated by the third and fourth passes that was subjected to a critical peak temperature for sigma precipitation. Ferrite content, measured using image analysis and Fisher FERITSCOPE technique, showed that the ferrite fraction moved toward 50/50% in the weld metal with an increasing number of reheating cycles. Finally, a schematic map showing an overview of the microstructure in the multipass SDSS weld was introduced.

Keywords
Multipass welding; Super-duplex stainless steel; Ferrite content; Sigma phase; Nitrides
National Category
Manufacturing, Surface and Joining Technology
Research subject
Production Technology; ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-14753 (URN)10.1007/s40194-019-00829-7 (DOI)000498097900001 ()2-s2.0-85075381068 (Scopus ID)
Funder
Vinnova, 2016-02834EU, Horizon 2020, 823786
Available from: 2019-12-12 Created: 2019-12-12 Last updated: 2020-01-30Bibliographically approved
Sreekanth, S., Hurtig, K., Joshi, S. V., Andersson, J. & Ghassemali, E. (2020). Effect of Direct Energy Deposition Process Parameters on Single-Track Deposits of Alloy 718. Metals, 10(1), 01-16, Article ID 96.
Open this publication in new window or tab >>Effect of Direct Energy Deposition Process Parameters on Single-Track Deposits of Alloy 718
Show others...
2020 (English)In: Metals, E-ISSN 2075-4701, Vol. 10, no 1, p. 01-16, article id 96Article in journal (Refereed) Published
Abstract [en]

The effect of three important process parameters, namely laser power, scanning speed and laser stand-off distance on the deposit geometry, microstructure and segregation characteristics in direct energy deposited alloy 718 specimens has been studied. Laser power and laser stand-off distance were found to notably affect the width and depth of the deposit, while the scanning speed influenced the deposit height. An increase in specific energy conditions (between 0.5 J/mm2 and 1.0 J/mm2) increased the total area of deposit yielding varied grain morphologies and precipitation behaviors which were comprehensively analyzed. A deposit comprising three distinct zones, namely the top, middle and bottom regions, categorized based on the distinct microstructural features formed on account of variation in local solidification conditions. Nb-rich eutectics preferentially segregated in the top region of the deposit (5.4–9.6% area fraction, Af) which predominantly consisted of an equiaxed grain structure, as compared to the middle (1.5–5.7% Af) and the bottom regions (2.6–4.5% Af), where columnar dendritic morphology was observed. High scan speed was more effective in reducing the area fraction of Nb-rich phases in the top and middle regions of the deposit. The <100> crystallographic direction was observed to be the preferred growth direction of columnar grains while equiaxed grains had a random orientation.

Keywords
laser metal deposition (LMD); columnar dendritic morphology; constitutional supercooling; columnar to equiaxed transition (CET); high deposition rate
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering; Production Technology
Identifiers
urn:nbn:se:hv:diva-14922 (URN)10.3390/met10010096 (DOI)000516827800096 ()
Available from: 2020-01-29 Created: 2020-01-29 Last updated: 2020-03-27Bibliographically approved
Devotta, A. M., Sivaprasad, P. V., Beno, T., Eynian, M., Hurtig, K., Magnevall, M. & Lundblad, M. (2019). A modified Johnson-Cook model for ferritic-pearlitic steel in dynamic strain aging regime. Metals, 9(5), Article ID 528.
Open this publication in new window or tab >>A modified Johnson-Cook model for ferritic-pearlitic steel in dynamic strain aging regime
Show others...
2019 (English)In: Metals, ISSN 2075-4701, Vol. 9, no 5, article id 528Article in journal (Refereed) Published
Abstract [en]

In this study, the flow stress behavior of ferritic-pearlitic steel (C45E steel) is investigated through isothermal compression testing at different strain rates (1 s-1, 5 s-1, and 60 s-1) and temperatures ranging from 200 to 700 °C. The stress-strain curves obtained from experimental testing were post-processed to obtain true stress-true plastic strain curves. To fit the experimental data to well-known material models, Johnson-Cook (J-C) model was investigated and found to have a poor fit. Analysis of the flow stress as a function of temperature and strain rate showed that among other deformation mechanisms dynamic strain aging mechanism was active between the temperature range 200 and 400 °C for varying strain rates and J-C model is unable to capture this phenomenon. This lead to the need to modify the J-C model for the material under investigation. Therefore, the original J-C model parameters A, B and n are modified using the polynomial equation to capture its dependence on temperature and strain rate. The results show the ability of the modified J-C model to describe the flow behavior satisfactorily while dynamic strain aging was operative. © 2019 by the authors. Licensee MDPI, Basel, Switzerland.

Place, publisher, year, edition, pages
MDPI AG, 2019
Keywords
flow stress; modified Johnson-Cook model; dynamic strain aging
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-13989 (URN)10.3390/met9050528 (DOI):000478818700046 ()2-s2.0-85066741813 (Scopus ID)
Funder
Swedish Research Council, 20110263, 20140130
Available from: 2019-06-20 Created: 2019-06-20 Last updated: 2020-02-19Bibliographically approved
Valiente Bermejo, M. A., Hurtig, K., Eyzop, D. & Karlsson, L. (2019). A New Approach to the Study of Multi-Pass Welds–Microstructure and Properties of Welded 20-mm-Thick Superduplex Stainless Steel. Applied Sciences, 9(6), Article ID 1050.
Open this publication in new window or tab >>A New Approach to the Study of Multi-Pass Welds–Microstructure and Properties of Welded 20-mm-Thick Superduplex Stainless Steel
2019 (English)In: Applied Sciences, E-ISSN 2076-3417, Vol. 9, no 6, article id 1050Article in journal (Refereed) Published
Abstract [en]

Type 2507 superduplex stainless steel 20 mm in thickness was multi-pass-welded with Gas Metal Arc Welding (GMAW) and Flux-Cored Arc Welding (FCAW) processes. Recommended and higher arc energies and inter-pass temperatures were used. Thermal cycles were monitored using a recently developed procedure involving the successive instrumentation of the multi-pass welds, pass by pass, by addition of thermocouples in each weld pass. The repeatability of temperature measurements and survival rate of more than 90% of thermocouples confirmed the reliability of the procedure. Reheating by subsequent passes caused a progressive increase in the austenite content of the weld metal. The as-deposited GMAW passes with higher-than-recommended arc energy showed the lowest presence of nitrides. Therefore, the cooling rate&mdash;and not the time exposed at the critical temperature range&mdash;seems to be the key factor for nitride formation. The welding sequence layout also plays an important role in the distribution of secondary phases. A larger amount and concentration of secondary austenite and &sigma;-phase was found for a larger number of subsequent passes in the immediate vicinity of a specific weld pass. The impact toughness exceeded requirements for all welds. Differences in absorbed energies were related to the amount of micro-inclusions found with the FCAW weld showing the lowest absorbed energies and highest amount of micro-inclusions. Pitting corrosion preferentially initiated in locations with secondary austenite and &sigma;-phase. However, in the absence of these secondary phases, the HAZ containing nitrides was the weakest location where pitting initiated. The results of this work have implications on practical welding for superduplex stainless steels: the current recommendations on maximum arc energy should be revised for large thickness weldments, and the importance of the welding sequence layout on the formation of secondary phases should be considered.

Place, publisher, year, edition, pages
MDPI, 2019
Keywords
multi-pass welding, nitrides, secondary austenite, superduplex stainless steel, thermal cycles, welding, sigma-phase
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-13730 (URN)10.3390/app9061050 (DOI)000465017200015 ()2-s2.0-85063719317 (Scopus ID)
Funder
Knowledge Foundation, 20140046
Available from: 2019-03-20 Created: 2019-03-20 Last updated: 2020-02-04
Hosseini, V., Hurtig, K., Eyzop, D., Östberg, A., Janiak, P. & Karlsson, L. (2019). Ferrite content measurement in super duplex stainless steel welds. Welding in the World, 63(2), 551-563
Open this publication in new window or tab >>Ferrite content measurement in super duplex stainless steel welds
Show others...
2019 (English)In: Welding in the World, ISSN 0043-2288, E-ISSN 1878-6669, Vol. 63, no 2, p. 551-563Article in journal (Refereed) Published
Abstract [en]

Approaches to determining ferrite fraction (%) and ferrite number (FN) were examined for super duplex stainless steel (SDSS) welds. A reference sample was produced by bead-on-plate gas–tungsten arc welding of a type-2507 SDSS plate. By comparing different etchants and measurement practices, it was realized that etching with modified Beraha followed by computerized image analysis (IA) was the most accurate and quickest technique to measure ferrite fraction, which determined the same ferrite fraction (68.0 ± 2.6%) as that measured by electron diffraction backscattered analysis (67.6 ± 2.3%). A Round Robin test was performed on a reference sample at University West, Swerea KIMAB, Outokumpu Stainless, and Sandvik Materials Technology to investigate the repeatability of the technique. The ferrite fraction measurements performed at different laboratories showed very small variations, which were in the range of those seen when changing microscope in the same laboratory. After verification of the technique, the relationship between ferrite fraction and ferrite number (measured with FERITSCOPE®) was determined using 14 single (root) pass welds, including butt, corner, and T-, V-, and double V-joint geometries. The best-fit equation found in this study was ferrite number (FN) = 1.1 × ferrite fraction (%). To conclude, the ferrite fraction technique suggested in the present paper was accurate and repeatable, which made it possible to determine a ferrite fraction–ferrite number formula for SDSS single-pass welds.

Keywords
Ferrite fraction, Ferrite number, Image analysis, Round Robin, Super duplex stainless stee, l Point counting
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-13198 (URN)10.1007/s40194-018-00681-1 (DOI)000462318600028 ()2-s2.0-85063276679 (Scopus ID)
Funder
Vinnova, 2016-02834Knowledge Foundation, 20140130
Note

First Online: 05 December 2018

Available from: 2018-12-19 Created: 2018-12-19 Last updated: 2020-02-04Bibliographically approved
Raza, T., Hurtig, K., Asala, G., Andersson, J., Svensson, L.-E. & Ojo, O. A. (2019). Influence of Heat Treatments on Heat Affected Zone Cracking of Gas Tungsten Arc Welded Additive Manufactured Alloy 718. Metals, 9(8), Article ID 881.
Open this publication in new window or tab >>Influence of Heat Treatments on Heat Affected Zone Cracking of Gas Tungsten Arc Welded Additive Manufactured Alloy 718
Show others...
2019 (English)In: Metals, E-ISSN 2075-4701, Vol. 9, no 8, article id 881Article in journal (Refereed) Published
Abstract [en]

The weldability of additive manufactured Alloy 718 was investigated in various heat-treated conditions. The microstructure of the base metal was examined in detail in order to understand the effect of different pre-weld heat treatments; i.e., solution, solution and aging, and hot isostatic pressing. After welding, the variation in total crack lengths, maximum crack length and the total number of cracks in the heat affected zone (HAZ) were used as criteria for the cracking susceptibility of each material condition where wrought Alloy 718 was used as the reference material. Selective laser melting (SLM) manufactured Alloy 718 was susceptible to HAZ cracking in all material conditions. Total crack lengths in HAZ were highest in the SLM as-built condition and lowest in the SLM hot isostatic pressed condition. The cracks that were found in the HAZ of the welded materials consisted of liquation cracks, with eutectic product surrounding the cracks, as well as cracks from which liquation products were absent.

Place, publisher, year, edition, pages
MDPI, 2019
Keywords
selective laser melting; Alloy 718; heat treatments; gas tungsten arc welding; heat affected zone cracking
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-14595 (URN)10.3390/met9080881 (DOI)000484510000071 ()2-s2.0-85073280907 (Scopus ID)
Available from: 2019-10-16 Created: 2019-10-16 Last updated: 2020-03-06
Hosseini, V., Wessman, S., Hurtig, K. & Karlsson, L. (2019). Predicting ferrite fractions in single pass super duplex stainless steel welds: thermal cycle analysis and phase transformation modeling. In: ESSC and DUPLEX 2019: 10th European Stainless Steel Conference - Science and Market, 6th European Duplex Stainless Steel Conference and Exhibition. Paper presented at 10th European Stainless Steel Conference - Science and Market, ESSC 2019 and 6th European Duplex Stainless Steel Conference and Exhibition, DUPLEX 2019; Vienna; Austria; 30 September 2019 through 2 October 2019 (pp. 180-197). Wien: Austrian Society for Metallurgy and Materials (ASMET)
Open this publication in new window or tab >>Predicting ferrite fractions in single pass super duplex stainless steel welds: thermal cycle analysis and phase transformation modeling
2019 (English)In: ESSC and DUPLEX 2019: 10th European Stainless Steel Conference - Science and Market, 6th European Duplex Stainless Steel Conference and Exhibition, Wien: Austrian Society for Metallurgy and Materials (ASMET) , 2019, p. 180-197Conference paper, Published paper (Refereed)
Abstract [en]

The relationship between welding process parameters, welding thermal cycle, and the final microstructure is of great importance for reliable fabrication of welded super duplex stainless steels (SDSS) structures. The present study was primarily aimed at investigating the relationship for root/single pass welding of type 2507 SDSS. Fourteen welds were produced using GMAW, GTAW, SAW, and SMAW with different joints geometries, plate thicknesses, and welding parameters. Thermal cycles were recorded using several thermocouples attached to the plates and thermocouples were also harpooned into the weld pool. Weld pool geometries and base metal dilution in the weld metal were determined for all welds. The general trend was that the ferrite fraction of the weld zone increased with increasing cooling rate and base metal dilution in the weld metal. The ferrite fraction was in the range 49-64% for all welds. Kinetics of austenite formation was modeled using computational thermodynamics (Thermo-Calc & DICTRA) to predict the ferrite fractions in the weld zone and calculated fractions were in good agreement with experimental results. Some conflicting results showed that in addition to dilution and cooling rate, the possible nitrogen loss must be taken into account when evaluating and predicting ferrite fraction. It was concluded that the above approach can be used for prediction of the ferrite fraction of super duplex stainless steel single pass welds. Â 2019 ESSC and DUPLEX 2019 - 10th European Stainless Steel Conference - Science and Market, 6th European Duplex Stainless Steel Conference and Exhibition. All rights reserved.

Place, publisher, year, edition, pages
Wien: Austrian Society for Metallurgy and Materials (ASMET), 2019
Keywords
Commerce; Cooling; Electric arc welding; Electric welding; Ferrite; Forecasting; Metals; Nickel steel; Phase transitions; Plates (structural components); Thermal cycling; Thermocouples; Welds, Computational thermodynamics; Dictra; Ferrite fraction; Kinetics of austenite formation; Simulation; Super duplex stainless steel; Welding process parameters; Welding thermal cycles, Duplex stainless steel
National Category
Manufacturing, Surface and Joining Technology
Research subject
Production Technology; ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-15015 (URN)2-s2.0-85079330776 (Scopus ID)
Conference
10th European Stainless Steel Conference - Science and Market, ESSC 2019 and 6th European Duplex Stainless Steel Conference and Exhibition, DUPLEX 2019; Vienna; Austria; 30 September 2019 through 2 October 2019
Funder
Vinnova, 2016-02834
Available from: 2020-02-24 Created: 2020-02-24 Last updated: 2020-02-24Bibliographically approved
Hosseini, V., Högström, M., Hurtig, K., Valiente Bermejo, M. A., Stridh, L.-E. & Karlsson, L. (2019). Wire-arc additive manufacturing of a duplex stainless steel: thermal cycle analysis and microstructure characterization. Welding in the World, 63(4), 975-987
Open this publication in new window or tab >>Wire-arc additive manufacturing of a duplex stainless steel: thermal cycle analysis and microstructure characterization
Show others...
2019 (English)In: Welding in the World, ISSN 0043-2288, E-ISSN 1878-6669, Vol. 63, no 4, p. 975-987Article in journal (Refereed) Published
Abstract [en]

The evolution of microstructures with thermal cycles was studied for wire-arc additive manufacturing of duplex stainless steel blocks. To produce samples, arc energy of 0.5kJ/mm and interlayer temperature of 150 degrees C were used as low heat input-low interlayer temperature (LHLT) and arc energy of 0.8kJ/mm and interlayer temperature of 250 degrees C as high heat input-high interlayer temperature (HHHT). Thermal cycles were recorded with different thermocouples attached to the substrate as well as the built layers. The microstructure was analyzed using optical and scanning electron microscopy. The results showed that a similar geometry was produced with 14 layers4 beads in each layerfor LHLT and 15 layers3 beads in each layerfor HHHT. Although the number of reheating cycles was higher for LHLT, each layer was reheated for a shorter time at temperatures above 600 degrees C, compared with HHHT. A higher austenite fraction (+8%) was achieved for as-deposited LHLT beads, which experienced faster cooling between 1200 and 800 degrees C. The austenite fraction of the bulk of additively manufactured samples, reheated several times, was quite similar for LHLT and HHHT samples. A higher fraction of secondary phases was found in the HHHT sample due to longer reheating at a high temperature. In conclusion, an acceptable austenite fraction with a low fraction of secondary phases was obtained in the bulk of wire-arc additively manufactured duplex stainless steel samples (35-60%), where higher austenite fractions formed with a larger number of reheating cycles as well as longer reheating at high peak temperatures (800-1200 degrees C).

Keywords
Duplex stainless steels; Additive manufacturing; GMAW; Thermal cycles; Austenite fraction; Secondary phases
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-13947 (URN)10.1007/s40194-019-00735-y (DOI)000468518900005 ()2-s2.0-85066099481 (Scopus ID)
Available from: 2019-06-11 Created: 2019-06-11 Last updated: 2020-02-03
Li, P., Hurtig, K., Högström, M., Svensson, L.-E. & Scotti, A. (2018). A contribution to the study of negative polarity in GMA welding. The International Journal of Advanced Manufacturing Technology, 95(5-8), 2543-2553
Open this publication in new window or tab >>A contribution to the study of negative polarity in GMA welding
Show others...
2018 (English)In: The International Journal of Advanced Manufacturing Technology, ISSN 0268-3768, E-ISSN 1433-3015, Vol. 95, no 5-8, p. 2543-2553Article in journal (Refereed) Published
Abstract [en]

GMAW using the electrode with negative polarity (DCEN) has been frequently suggested as a potential means of increasing production capacity. The objective of this work was to further study the performance of negative polarity in GMAW of carbon steels. In this project phase, bead-on-plate welds were carried out in flat position to assess the effect of different potential shielding gas compositions on bead geometry, finishing and spattering. The characteristics were compared with DCEP at the same current, but depositing the same volume of material per unit of length (more industrial related comparison). The arc length was kept the same by adjusting voltage to reach shortest arcs, yet with suitable non short-circuiting metal transfer mode. An approach to measure bead convexity was also proposed and assessed. The results showed that DCEN is feasible as a means of increasing GMAW production capacity. However, to become DCEN applicable with GMAW, the results suggest an Ar based blend with around 6.5 % of O2 is the most appropriate shielding gas, as much as that there is a demand for a standard electronic controlled power source able to work in constant current mode. 

Keywords
Welding; Production; GMAW; Negative Polarity; Fusion rate; Weld bead geometry
National Category
Other Mechanical Engineering Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering; Production Technology
Identifiers
urn:nbn:se:hv:diva-11817 (URN)10.1007/s00170-017-1349-z (DOI)2-s2.0-85035104454 (Scopus ID)
Projects
Maplab
Funder
Region Västra Götaland, RUN 612-0254-15
Note

Funders: Swedish Agency for Economic and Regional Growth, 20200328.

Available from: 2017-11-26 Created: 2017-11-26 Last updated: 2020-04-02Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-0234-3168

Search in DiVA

Show all publications