The effects of postweld heat treatment and isothermal aging on T92 steel heat-affected zone mechanical properties of T92/TP316H dissimilar weldments

Cross-weld hardness profile, notch-tensile strength, and impact toughness of T92 steel heat-affected zone (T92 HAZ) of dissimilar T92/TP316H welds were studied in dependence of their postweld heat treatment (PWHT) and subsequent long-term aging. Two weldments series were individually subjected to either single-step tempering PWHT or a modified two-step renormalizing and tempering PWHT. Subsequently, the welds were isothermally aged at 625 degrees C for durations from 500 up to 11,000 h. The single-step PWHT preserved sharp hardness gradient of T92 HAZ, whereas the two-step PWHT led to the hardness values equalization. The T92 HAZ of the weldment after the two-step PWHT exhibited initially lower strength and higher toughness, compared to the weldment after the single-step PWHT. However, after long-term aging a more suitable combination of T92 HAZ mechanical properties i.e., the higher toughness and acceptable strength exhibited the weldments processed by single-step PWHT.