Abstract
This study investigated the impact of electromagnetic stirring (EMS) on nickel-base alloy welds prepared with the gas tungsten arc welding process. Alloy 52 and its variants, Alloy 52M and Alloy 52MSS, were carefully evaluated with their weld microstructure and mechanical properties. The results showed that the welds exhibited a typical microstructure of dendrites, and that the dendrites could be refined by electromagnetic stirring. Meanwhile, with an application of EMS, the precipitates became smaller and more evenly distributed in the inter-dendritic areas. Ti(N,C)s, Nb/(Nb,Si)Cs, and large-scale Laves phase with (Nb,Mo,Ti)Cs were the precipitates present in the Alloy 52, Alloy 52M, and Alloy 52MSS welds, respectively. With the refined microstructure, both Alloy 52 and Alloy 52M welds were observed to have an increase in their tensile strength, with a decrease in their elongations. Comparatively, for the Alloy 52MSS weld, the tensile strength was enhanced along with a slight increase in elongation. Deep and dense dimples were a dominant feature of low-Nb-additions welds, and dendrite-like features were found prevalent among the Alloy 52MSS welds. With EMS, the dimples of Alloy 52 welds and the dendrite-like features of Alloy 52MSS welds became finer, while the dimples of Alloy 52M welds grew coarser.
Highlights
Alloy 52, a weld alloy with a Cr content up to 30-wt%, has superior resistance to intergranular stress corrosion cracking (IGSCC) and is often used for repairing the degradedAlloy 82/182 welds in nuclear power plants [1,2,3,4]
In spite of the concern of IGSCC, Alloy 182 is less susceptible to ductility dip cracking (DDC)
This is attributed to the moderate addition of Nb, resulting in tortuous grain boundaries, and abundant coarse Nb precipitates on the grain boundary to block the initiation and propagation of DDC [8,9,10]
Summary
Alloy 52, a weld alloy with a Cr content up to 30-wt%, has superior resistance to intergranular stress corrosion cracking (IGSCC) and is often used for repairing the degradedAlloy 82/182 welds in nuclear power plants [1,2,3,4]. In spite of the concern of IGSCC, Alloy 182 is less susceptible to DDC. This is attributed to the moderate addition of Nb, resulting in tortuous grain boundaries, and abundant coarse Nb precipitates on the grain boundary to block the initiation and propagation of DDC [8,9,10]. On this account, Alloy 52M was developed to mitigate DDC by adding.
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