Microstructures and Mechanical Properties of V-Containing Mo₂NiB₂ Hard Alloys

Abstract

Microstructures and mechanical properties of V(Vanadium)-containing MO₂NiB₂ hard alloys were studied for Ni-6 mass%B-58.6 mass%Mo-(0-12.5) mass%V alloys.
Boride (M₃B₂, M:Mo, Ni, V) particle size decreased with increasing V content larger than 5μm for the 0 mass%V alloy and about lμm for the 12.5 mass%V alloy. The crystal structual change of the boride from orthorhombic to tetragonal was responsible for the particle size reduction. The highest transverse-rupture strength (TRS) of 2.5 GPa was obtained for the 12.5 mass%V alloy which exhibited the smallest particle size. The 12.5 mass%V alloy showed small decrease in hardness at high temperatures at 1073 K.