Hot Cracks as Stress Corrosion Cracking Initiation Sites in Laser Welded Corrosion Resistant Alloys

Abstract

Although hot cracks at weld surfaces of corrosion resistant alloys (CRAs) might provide access to respective aggressive media and thus, might provide the conditions for a local potential and pH drop, the interaction between hot cracking and corrosion phenomena has not been investigated up to the present. This particularly concerns the initiation of stress corrosion cracking inside such crevices.

As a first approach to clarify the influence of hot cracks on corrosion resistance, considering particularly stress corrosion cracking, hot crack afflicted laser welds of three different CRAs have been subjected to a series of different corrosion tests.

Besides the fact that the Drop Evaporation (DE) Test represents a more realistic procedure than standard immersion tests it turned out that hot cracks can obviously represent an initiation site of stress corrosion cracking in the austenitic stainless steel AISI 309 (German No. 1.4828). The susceptibility of such hot crack afflicted laser welds to stress corrosion cracking (SCC) significantly depends on temperature and chloride concentration of the test environment In comparison, the high nitrogen austenitic stainless steel AISI S 34565 (German No. 1.4565) did not exhibit any stress corrosion cracking associated with hot cracking. This material exhibited pitting corrosion and stress corrosion only in the base material. The Alloy 50 (German No. 2.4850), a Nickel based material, was susceptible to pitting corrosion, but showed no tendency towards stress corrosion cracking at all.