Abstract
Ni-6mass%B-55.9mass%Mo-Xmass%Mn model cermets with four levels on Mn content from 10 to 25mass% were prepared to investigate the effects of Mn on the structure and properties of Mo_2NiB_2-Ni cermets. The powder mixtures prepared from pure Mo, pure Mn, carbonyl Ni and MoB were boll-milled in acetone. After drying, the milled powder were pressed to green compacts and sintered in vacuum for 1.2ksec at 1573 and 1598K. The cermet additions of 15mass%Mn exhibits a tetragonal Mo_2NiB_2 (M_3B_2) complex boride. Mn as well as Cr and V changed a crystal structure of the Mo_2NiB_2 complex boride from orthorhombic to tetragonal at 15 mass% Mn addition. However, transverse rupture strength (TRS) and hardness decreased with increasing Mn containing. The decrease of TRS and hardness was caused by residual pores and Mn oxides. Therefore there needs to be a tailoring a sintering condition so that the cermets eliminate those defects.
