Hydrogen induced cracking and stress corrosion cracking behavior of the weld metals in 17‐4 precipitation hardening stainless steel after double over aging treatment

Abstract This research studied the effect of two‐stage over aging treatment on corrosion behavior of the weld metals in the 17‐4 precipitation hardening stainless steel. Gas tungsten arc welding was performed under solution annealed condition. After the welding, weld metal was subjected to double over aging treatments. Hydrogen induced cracking and stress corrosion cracking standard tests were carried out on weld metals before and after ageing treatment. Charpy impact test and microhardness test were conducted to evaluate the mechanical properties of weld metals. Microstructural examinations of the welding zones were performed by the optical microscope and field emission scanning electron microscope. The results showed that the as‐weld lath and coarse martensite were transferred to severely tempered martensite after over aging treatment with the formation of reversed austenite. In the latter case, the reversed austenite was about 30 % compared to 7 % before over aging treatment. The over aged weld metals were significantly more resistant to hydrogen induced cracking, and exhibited a longer time‐to‐failure in stress corrosion cracking test. The weld metal in the as‐weld condition in hydrogen induced cracking test showed severe cracking and failed rapidly in the stress corrosion cracking test.