Abstract
Effects of solidification mode and low-temperature aging on stress corrosion cracking (SCC) behavior of two types of 316L stainless steel weld metal with different solidification modes in high-temperature water have been investigated. The hardness of ferrite phase has increased with aging time, while the hardness of austenite phase has stayed the same. The nanometer-scaled mottled aspects have been observed in δ-ferrite of welds with 335 ℃ aging for 8000 hours by transmission electron microscope observation. This characteristic suggests that spinodal decomposition has occurred in δ-ferrite with 335 ℃ aging. The results of SCC test would suggest that threshold stress level for SCC initiation is lower for the austenite-ferrite (AF) mode weld compared to the ferrite-austenite (FA) mode weld. From SCC propagation point of view, cracks in the FA mode weld have propagated along δ/γ interface; on the other hand, those in the AF mode weld have propagated mainly along γ/γ interface, and have been arrested at island-type δ-ferrite in many cases. Above characteristics have been confirmed regardless of aging. No significant decrease in corrosion resistance of δ-ferrite has been observed for welds with 335 ℃ aging up to 13200 hours.
