Method for evaluating yield strength of laser weldments of maraging steels using hardness test

Abstract

This paper describes a new method for predicting fracture location, joint efficiency and yield strength of laser weldments of Fe–Cr–Ni–Mo–Ti–Cu stainless maraging steel and 18 Ni maraging steel using hardness distribution analysis and incorporating Tabor's relationship between hardness and yield strength for metallic materials. Fracture location of weldment can be determined by a parameter L_F, hardness ratio of heat affected zone (HAZ) to fusion zone (FZ) or HAZ to parent material zone (PMZ). Whether or not the yield strength of weldments is improved as compared with as received material via various post-weld heat treatments can be estimated qualitatively by a parameter Y_I, hardness ratio of predicted fracture location to as received parent material. The yield strength of weldments is well predicted in as weld and heat treated conditions using hardness modeling, the maximum errors of predicted yield strength are 3·3 and 2·5 of measured yield strength for weldments of Fe–Cr–Ni–Mo–Ti–Cu and 18Ni maraging steels respectively. These results confirm the usefulness of the proposed method as engineering tool to predict yield strength of maraging steels laser weldments in different heat treated conditions without performing tensile tests, and to optimize post-weld heat treatments.