Determination of low temperature mechanical behaviour of the heat affected zone of a P91 steel weld using the small punch test technique

Abstract

The Small Punch (SP) test technique has been shown to be a promising method in determining the degradation of mechanical properties in operating components as it enables sampling from very localized areas; for instance the critical zones of a weldment and its HAZ (Heat Affected Zone). In this study, SP tests were carried out in order to determine the low temperature mechanical behaviour of the individual regions of P91 steel weld; base metal (BM), HAZ-FG (Heat Affected Zone-Fine Grained) and HAZ-CG (Heat Affected Zone-Coarse Grained). Microhardness measurements, optical and scanning electron microscopy methods were used for a better understanding of microstructure-property relationship and fracture mechanisms. As a result of the study it was possible to observe the increase in strength and ductility in the HAZ-FG compared to the BM and HAZ-CG which was more pronounced at lower temperatures. Consequently HAZ-FG had higher SP fracture energies and a lower transition temperature than the other zones.