Special Issue "Welding Metallurgy and Weldability of Superalloys"

A special issue of Metals (ISSN 2075-4701).

Deadline for manuscript submissions: closed (31 July 2019).

Special Issue Editor

Assoc. Prof. Joel Andersson
E-Mail Website
Guest Editor
Division of Welding Technology, Department of Engineering Science, University West, SE-461 86 Trollhättan, Sweden
Interests: additive manufacturing; welding and weldability testing; materials engineering and materials physics
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Special Issue Information

Dear Colleagues,

Fabrication and welding of structural superalloy components for aero-engines, land-based gas turbines, as well as for the energy sector (i.e., steam boilers) continues to be of high importance to the manufacturing industry. The components, which utilize superalloys, are usually referred to as the most demanding and where welding of these most often plays an essential role, not only in manufacturing, but also in repair and re-manufacturing. It is therefore of utmost importance that the welds used in the design are of suitable quality to account for the demanding environment. Numerous challenges exist to welding these alloys and caution needs to be exercised in order to avoid problems such as hot cracking or strain age cracking. In addition, there is a wide range of weldability testing methods available to predict, for example, susceptibility towards hot cracking, where each method has its unique characteristics. Nevertheless, the available weldability testing methods play a vital role in the fundamental study of the root cause for, for example, weld cracking, which can be further enhanced by characterization as well as simulation. This Special Issue intends to offer a dedicated platform for sharing new findings, communicating views about the accomplishments and future directions in superalloy welding and weldability testing research. We welcome reviews and original research articles in the areas of welding metallurgy, weldability, and associated topics of superalloys, achieved through either experimental techniques or theoretical calculations.

Assoc. Prof. Joel Andersson
Guest Editor

Manuscript Submission Information

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Keywords

  • welding metallurgy
  • weldability
  • varestraint
  • gleeble
  • hot cracking
  • strain age cracking
  • HAZ liquation cracking
  • solidification cracking
  • superalloys

Published Papers (3 papers)

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Research

Open AccessArticle
Comparison of Hot Cracking Susceptibility of TIG and Laser Beam Welded Alloy 718 by Varestraint Testing
Metals 2019, 9(9), 985; https://doi.org/10.3390/met9090985 - 05 Sep 2019
Abstract
Reduced hot cracking susceptibility is essential to ensure the flawless manufacturing of nickel superalloys typically employed in welded aircraft engine structures. The hot cracking of precipitation strengthened alloy 718 mainly depends on chemical composition and microstructure resulting from the thermal story. Alloy 718 [...] Read more.
Reduced hot cracking susceptibility is essential to ensure the flawless manufacturing of nickel superalloys typically employed in welded aircraft engine structures. The hot cracking of precipitation strengthened alloy 718 mainly depends on chemical composition and microstructure resulting from the thermal story. Alloy 718 is usually welded in a solution annealed state. However, even with this thermal treatment, cracks can be induced during standard industrial manufacturing conditions, leading to costly and time-consuming reworking. In this work, the cracking susceptibility of wrought and investment casting alloy 718 is studied by the Varestraint test. The test is performed while applying different welding conditions, i.e., continuous tungsten inert gas (TIG), low frequency pulsed TIG, continuous laser beam welding (LBW) and pulsed LBW. Welding parameters are selected for each welding technology in order to meet the welding quality criteria requested for targeted aeronautical applications, that is, full penetration, minimum cross-sectional welding width and reduced overhang and underfill. Results show that the hot cracking susceptibility of LBW samples determined by the Varestraint test is enhanced due to extended center line hot cracking, resulting in a fish-bone like cracking pattern. On the contrary, the minor effect of material source (wrought or casting), grain size and pulsation is observed. In fact, casting samples with a 30 times coarser grain size have shown better performance than wrought material. Full article
(This article belongs to the Special Issue Welding Metallurgy and Weldability of Superalloys)
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Open AccessArticle
Influence of Heat Treatments on Heat Affected Zone Cracking of Gas Tungsten Arc Welded Additive Manufactured Alloy 718
Metals 2019, 9(8), 881; https://doi.org/10.3390/met9080881 - 10 Aug 2019
Cited by 1
Abstract
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. [...] Read more.
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. Full article
(This article belongs to the Special Issue Welding Metallurgy and Weldability of Superalloys)
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Open AccessArticle
The Comparison of Cracking Susceptibility of IN52M and IN52MSS Overlay Welds
Metals 2019, 9(6), 651; https://doi.org/10.3390/met9060651 - 04 Jun 2019
Abstract
Overlay-welding of IN52M and IN52MSS onto CF8A stainless steel (SS) was conducted by a gas tungsten arc welding process in multiple passes. An electron probe micro-analyzer (EPMA) was applied to determine the distributions and chemical compositions of the grain boundary microconstituents, and the [...] Read more.
Overlay-welding of IN52M and IN52MSS onto CF8A stainless steel (SS) was conducted by a gas tungsten arc welding process in multiple passes. An electron probe micro-analyzer (EPMA) was applied to determine the distributions and chemical compositions of the grain boundary microconstituents, and the structures were identified by electron backscatter diffraction (EBSD). The hot cracking of the overlay welds was related to the microconstituents at the interdendritic boundaries. The formation of γ-intermetallic (Ni3(Nb,Mo)) eutectics was responsible predominantly for the hot cracking of the 52M and 52MSS overlays. The greater Nb and Mo contents in the 52MSS overlay enhanced the formation of coarser microconstituents in greater amounts at the interdendritic boundaries. Thus, the hot cracking sensitivity of the 52MSS overlay was higher than that of the 52M overlay. Moreover, migrated grain boundaries were observed in the 52M and 52MSS overlays but did not induce ductility dip cracking (DDC) in this study. Full article
(This article belongs to the Special Issue Welding Metallurgy and Weldability of Superalloys)
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