Welding Metallurgy of
01 Jan 1987-
About: The article was published on 1987-01-01 and is currently open access. It has received 991 citations till now. The article focuses on the topics: Welding.
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01 Jan 2018
TL;DR: In this paper, the effect of two HIP treatments commonly employed in the aerospace industry on the weldability of the cast Alloy 718 was also addressed, including the assessment of five different pseudo-HIP treatments and the weldingability of two cast superalloys is compared.
Abstract: Precipitation hardened Ni- and Ni-Fe- based superalloys, used in hot structural components for aero engines, are subjected to hot cracking phenomena during manufacturing and specifically in welding. This type of cracking involves metallurgical reactions from the liquid phase in concomitance to weld restraints. Hot cracking is more pronounced during the welding of cast superalloys compared to its wrought counterparts owing to the larger inhomogeneity in the cast material. Cast structural components must therefore undergo a hot isostatic pressing (HIP) treatment prior to welding for closing any pores from the casting process and homogenizing the material. The current study is about the effect of two HIP treatments commonly employed in the aerospace industry on the weldability of the cast Alloy 718. Moreover, the weldability of the recently introduced cast version of ATI® 718PlusTM is also addressed, including the assessment of five different pseudo-HIP treatments and the weldability of the two cast superalloys is compared. Testing was conducted using the Varestraint (Variable-Restraint) weldability testing technique, where test plates were welded by a robot and at the same time bended to achieve external restraint. Welding and test parameters were the same for all the conditions. The hot cracking susceptibility of cast Alloy 718 was found to be worse with increasing HIP treatment temperature. It was found that HIP treatment conducted at 1190°C/4h gave higher crack susceptibility than the one at 1120°C/4h. Cast ATI® 718PlusTM was heat treated using short dwell heat treatments for 4h at 1120°C, 1160°C and 1190°C and long dwell heat treatments for 24h at both 1120°C and 1190°C, respectively. The cracking susceptibility was found to be related to the heat treatment dwell time rather than the temperature. The heat treatment at 4h dwell time exhibited lower amount of cracking than the 24h dwell heat treatment. Considering the comparative heat treatments at 1120°C/4h and 1190°C/4h, the new cast superalloy ATI® 718PlusTM was found to have lower cracking susceptibility than the cast Alloy 718.
5 citations
Cites background from "Welding Metallurgy of"
...This is not a concern when welding at low speeds; elliptical shaped welds lead to a smooth transition of the columnar grains at the weld centre [22]....
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...Generally, the lower the solidification temperature, the wider the temperature range at which the liquid will exist and this can aggravate the cracking tendency [15], [22]....
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TL;DR: In this article, a microestrutura and a dureza of a liga de NiCr utilizada in proteses odontologicas soldadas com brasagem and a laser were investigated.
Abstract: Investigou-se a microestrutura e a dureza de uma liga de NiCr utilizada em proteses odontologicas soldadas com brasagem e a laser. Verificou-se que na brasagem o metal base e o cordao de solda apresentaram microestruturas distintas, e que na soldagem a laser identificou-se tres regioes: o cordao de solda, a zona afetada pelo calor - ZAC e o metal base. O metal base da liga NiCr apresentou uma microestrutura dendritica grosseira com uma estrutura eutetica interdendritica, a regiao da solda por brasagem apresentou uma morfologia dendritica grosseira com a presenca de precipitados e porosidades e na soldagem a laser uma estrutura dendritica refinada. Estas microestruturas foram condizentes com as energias de soldagem fornecidas em cada processo. Os resultados dos ensaios de tracao da solda a laser foram superiores aos obtidos para a solda por brasagem. Para ambos os processos de soldagem a dureza no cordao de solda foi maior do que o metal base, na soldagem a laser a dureza na ZAC foi menor do que no metal base, e sua extensao foi menor que 1mm devido a pequena energia transferida ao metal base. O emprego da soldagem a laser em pecas proteticas de pequenas espessuras nao devera causar distorcao significativa, sendo promissor na substituicao da brasagem nesta aplicacao.
5 citations
Journal Article•
TL;DR: In this paper, the hardness of weld and heat affected zone (HAZ) was measured with a polynomial regression technique using 10 rectangular single V-butt manually arc welded mild steel specimens having bevel angle 60˚ and 70˚.
Abstract: Hardness is a very important mechanical property of materials. But during welding high heating and rapid cooling influence the hardness of the weld as well as heat affected zone (HAZ). In the present investigation, 10 rectangular single V-butt manually arc welded mild steel specimens having bevel angle 60˚ and 70˚ (5 specimens each) have been experimented with. The hardness of weld as well as heat affected zone (HAZ) so measured have been correlated with heat input rate using polynomial regression technique. The equations, thus, derived have been used to find out the effect of heat input rate on the hardness of weld as well as heat affected zone (HAZ). By these equations also the optimum hardness of weld and heat affected zone (HAZ) at minimal heat input rate for 60˚ and 70˚ bevel angle weldments have been found out. Also a comparison of optimal hardness for minimal heat input rate of weld and heat affected zone (HAZ) between 60˚ and 70˚ bevel angle weldments have been done.
5 citations
Cites methods from "Welding Metallurgy of"
...…experimental based polynomial regression technique were used to obtain the required information about the effects of heat input rate on the hardness of weld as well as heat affected zone (HAZ) for mild steel weldments (Linnert et al., 1994; Patchett, 1987; Adler et al., 1975 and Fisher, 1975)....
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TL;DR: In this paper, the microstructural characteristics, metallurgy, microhardness, and tensile strength of AZ31 and AZ61 magnesium alloy weldments, fabricated in a CO2 laser welding process with the adjustment of various parameters.
Abstract: This study investigated the microstructural characteristics, metallurgy, microhardness, and tensile strength of AZ31 and AZ61 magnesium alloy weldments, fabricated in a CO2 laser welding process with the adjustment of various parameters. The results show that the AZ31 weldment contains equiaxed grains within the fusion zone (FZ). By contrast, the FZ of the AZ61 weldment contains refined cellular grains and the partially melted zone (PMZ) contains bulk grains. We infer that the difference in aluminum content between the two magne- sium alloys results in different supercooling rates and solid grain structures. For both weldments, the ultimate tensile strength (UTS) de- creases following the CO2 laser welding process. However, no significant difference is noted between the UTS of the two weldments, sug- gesting that tensile strength is insensitive to the Al content of the magnesium alloy. The CO2 laser welding process is shown to increase the microhardness of both magnesium alloys. Furthermore, grain refinement is responsible for the maximum hardness in the FZ of both weld- ments. The AZ61 weldment has a higher content of Al, resulting in a greater grain refinement.
5 citations
Cites background from "Welding Metallurgy of"
...According to the theory of welding metallurgy [15], the mode of solidification changes the grain morphology as the temperature gradient decreases....
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References
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