The safe and reliable operation of pressurized water reactors (PWRs) depends on the integrity of structural material. In particular, the failure of steam generator (SG) tubes on the secondary side is one of the major concerns of operating nuclear power plants. To establish remediation techniques and manage damage, it is necessary to articulate the mechanism through which various impurities affect the SG tubes. This research aims to understand the effect of impurities (e.g., S, Pb, and Cl) on the stress corrosion cracking of Alloy 600 and 690.
Nickel alloys, despite their good strength properties at high temperature, are characterized by limited weldability due to their susceptibility to hot cracking. So far, theories describing the causes of hot cracking have focused on the presence of impurities in the form of sulphur and phosphorus. These elements form low-melting eutectic mixtures that cause discontinuities, most frequently along solid solution grain boundaries, under the influence of welding deformations. Progress in metallurgy has effectively reduced the presence of sulphur and phosphorus compounds in the material, however, the phenomenon of hot cracking continues to be the main problem during the welding of nickel-based alloys. It was determined that nickel-based alloys, including Inconel 617, show a tendency towards hot cracking within the high-temperature brittleness range (HTBR). There is no information on any structural changes occurring in the HTBR. Moreover, the literature indicates no correlations between material-related factors connected with structural changes and the amount of energy delivered into the material during welding.
This article presents identification of correlations between these factors contributes to the exploration of the mechanism of hot cracking in solid-solution strengthened alloys with an addition of cobalt (e.g. Inconel 617). The article was ended with development of hot cracking model for Ni-Cr-Mo-Co alloys.