PITTING BEHAVIOR OF TYPE-17-4 PH STAINLESS-STEEL WELDMENTS

Electrochemical methods of measuring pitting potentials (E(pit)) were used to study the pitting resistance of type 17% Cr-4% Ni (17-4, UNS S17400) precipitation hardenable (PH) stainless steel (SS) weldments, The main objectives were to evaluate the pitting resistance of the base metal, the heat affected zone (HAZ), and the weld metal portions of 17-4 PH SS welds welded autogenously using the gas tungsten are welding (GTAW) process. Effects of different preweld and postweld heat treatments (PWHT) and of the weld heat input on pitting resistance were studied. Results showed a solution-treated base metal had a relatively lower pitting resistance. In contrast, aging preceded by solution treatment improved pitting resistance. Direct peak aging after welding improved pining resistance of the weld metals, but it decreased resistance of the HAZ, Welding with relatively lower weld heal input decreased the pitting resistance of the weld metals, but the reverse occurred in the case of the HAZ. Solution treatment followed by peak aging nullified effects of the weld heat input and the preweld heat treatments on pitting resistance of the different portions of the weldment. This heat treatment produced relatively higher pitting resistance in all portions of the weldment.