Effect of directional anisotropy on mechanical properties of 9Cr Ferritic/Martensitic ODS steels processed by mechanical alloying and powder forging

Abstract

The present work investigates the feasibility of the powder forging route as a novel approach for the consolidation of oxide dispersion strengthened (ODS) steel powders. Mechanically alloyed powder of the composition Fe-9Cr-2 W-0.2Ti-0.12 C-0.35Y2O3 was filled in a mild steel can and loose sintered in a reducing atmosphere at 1200 °C after which it was forged in a channel die using a friction screw forging machine. The forged ODS steel was investigated in terms of residual porosity, microstructure, hardness and tensile properties. Density as well as hardness variation was determined along both the forging directions, i.e., longitudinal and transverse. In the transverse direction density, hardness and tensile strength was slightly higher as compared to that in the longitudinal direction. Powder forging led to the elimination of the prior particle boundaries (PPB) network in the final forged slab. Further, near isotropic mechanical properties and homogeneous chemical composition were obtained throughout the forged sample. The proposed powder forging route has significant potential as an alternative consolidation process to hot isostatic pressing (HIP) and hot extrusion to produce ODS steel for nuclear applications.