Effect of W Content on the Properties and Structure of Cr-containing Mo₂NiB₂ Base Hard Alloys

Abstract

The properties of a complex (Mo, Ni) boride influenced by additions of W were investigated in Mo-Ni-Cr-W-B sintered alloys where the boride has the tetragonal crystal structure due to solid solutioning of Cr. Additions of W lead to partition of W primarily into the complex boride, resulting in a stoichiometric change of the tetragonal boride from Mo₂(Ni, Cr)B₂ to (Mo, W)_5-x(Ni, Cr)_xB₃ around 10mass%W. The alloys having the tetragonal Mo₂(Ni, Cr)B₂ boride with W in the boride maintained high levels of transverse-rupture strength(TRS) and hardness due to small particle size of the boride up to 5mass%W. The stoichiometric change of the boride by additions of W caused increase in hardness and decrease in TRS due to increased volume fractions of the boride at the given boron content.