The Effect of Microstructure and Welding-Induced Plasticity on the Strength of Ni–Mo–Cr Alloy Welds

Abstract

The mechanical performance of a Ni–Mo–Cr (GH3535) alloy weldment, produced using a matching filler metal, was assessed and compared to the surrounding parent metal. Ambient-temperature mechanical characterisation included hardness testing, small punch testing and uniaxial tensile testing, while a crystal plasticity finite element model was used to assess the impact of crystallographic texture on the mechanical properties. Despite the similar chemical composition, the weld metal exhibited superior strength and ductility to that of the parent metal. The higher strength was primarily attributed to the high dislocation density in the weld metal imbued by the welding-induced thermo-mechanical loading. In contrast, the ductility difference was attributed to M₆C carbide stringers in the parent metal that initiated fracture at lower strains than for the weld metal, with the latter containing much finer, well-dispersed M₆C carbides.

Keywords: mechanical properties, welding, microstructure, NiMoCr alloy, Plasticity