The heat affected zone of X20Cr13 martensitic stainless steel after multiple repair welding: Microstructure and mechanical properties assessment

Abstract

Multiple repair welding of X20Cr13 martensitic stainless steel was performed using gas metal arc welding. The groove for repair welding was designed such that the heat affected zone (HAZ) of each repair welding sequence remained the HAZ of the previous repair (i.e. cyclic weld removal and repair welding was done). After post weld heat treatment, microstructure and mechanical properties of the HAZ were investigated during 0–9 repairs. Refinement of primary austenite grains in the HAZ was observed (from 2.8 ASTM grain size in the zero-repair sample to 6.3 after the ninth repair), increasing the impact toughness (from 34J to 63J, respectively). Moreover, HAZ micro-hardness decreased as repair welding continued due to sequential disintegration of the chromium carbides network at grain/sub-grain boundaries, promoting ductile fracture behavior. It was finally concluded that multiple repair welding has no detrimental effects on microstructure and mechanical properties of X20Cr13 stainless steel and increases HAZ impact toughness and promotes ductile fracture.