A Study for Influence of PWHT on Sensitization microstructure of AISI 316Ti Stainless Steel Weld Joints

The aim of this study was to investigate the influence of post weld heat treatment on microstructure of AISI 316Ti stainless steel. This study was started from welding 316Ti pipe with ER318Si filler metal, then the welded samples were post-weld heat treated at 800, 850, 900, 950, 1000, and 1050 ºC for various times of 1, 4, and 10 hours. Each specimen was analyzed by using microstructure examination at base metal, heat affected zone, and welded area to study for size and distribution of TiC, and volume fraction of chromium carbide. After that, the inter-granular corrosion testing (IGC test) was performed as per ASTM A262-15 Practice-E standard to find the appropriate heat treatment time and temperature. The results showed that, at the temperature above 950 ºC, no severe inter-granular corrosion was observed at heat affected zone, but severe corrosion was found at weldment area. Scanning electron microscopy (SEM) results showed that, at 1050 ºC heat treatment temperature, the corrosion was significantly decreased comparing to that of 1000 ºC. Also, the inter-granular corrosion tended to increase when post weld heat treatment time increased.