Microstructure and Mechanical Properties of Autogeneous GTA Weldments of Reduced-Activation Ferritic/Martensitic Steel and the Effects of Alloying Elements

Abstract

Five reduced-activation ferritic/martensitic (RAFM) steels containing different contents of Cr, Ta, and Ti were prepared and the weldability of these alloys were evaluated by autogeneous gas tungsten arc (GTA) welding. After welding, post weld heat treatment (PWHT) was performed at temperatures of approximately 730-750 ℃. The microstructures of all alloys after PWHT consisted of a tempered martensite matrix and two types of precipitates, namely, M₂₃C₆ and MX. Both the tensile and yield strength of the GTA welds increased with an increase in Cr and Ta contents due to the enhanced solid solution and precipitation strengthening. An increase in Ti content promoted the precipitation of fine MX particles and thereby suppressed the precipitation of M₂₃C₆ carbide. This improved the impact toughness without a considerable loss of strength.