Variation in the Type IV cracking behaviour of a high Cr steel weld with post weld heat treatment

In this study creep tests were conducted on P122 steel cross weld specimens at 70 MPa after post weld heat treatment (PWHT) for different durations. Results indicated that the duration of PWHT did not influence the rupture time and all the specimens failed in a typical Type IV manner. However, differences were observed with respect to creep damage and microstructural changes that occurred in the fine grained heat affected zone (FGHAZ), the location of the fracture. It appears that factors other than changes in microstructure also affect the rupture life. One such factor could be the heterogeneity introduced in the weld joint due to the existence of different zones like weld metal, coarse grained HAZ (CGHAZ), FGHAZ and base metal, which differ vastly in their properties