Alterations of Boride Particle Coarsening by an Addition of Cr to a Mo-Ni-B Alloy during Liquid Phase Sintering

Liquid phase assisted reaction sintering of Mo-Ni-Cr-B alloys results in cermets consisting of a M₃B₂ (M: Mo, Cr, Ni) boride and metallic Ni alloy. The presence of a liquid phase drastically enhances particle coarsening kinetics as well as densification processes of green compacts during sintering. Cr addition to a Mo-Ni-B alloy influences the size and morphology of M₃B₂ particles in contact with the liquid phase. The crystal structure of M₃B₂ changes from orthorhombic to tetragonal due to the addition of 10 mass% of Cr. The paper discusses the effect of Cr on the microstructural evolution of Mo-Ni-Cr-B alloys in connection with the crystal structure transformation of the boride phase.