Production of Mo2MB2-type (M = Ni, Fe, Co) ternary boride containing alloys by self-propagating high temperature synthesis

Abstract

In this study, the production of Mo2MB2 (M: Ni, Fe, and Co) ternary boride containing alloys from their oxides by aluminothermic self-propagating high-temperature synthesis (SHS) method was investigated. The influence of different initial reactant ratios on the concurrent synthesis of reinforcement and matrix phases was studied. The thermochemical modeling studies were conducted to estimate the adiabatic temperature (Tad) change as well as high-temperature products. The phases, microstructure and chemical composition of the products were analyzed by X-ray diffraction, scanning electron microscopy (SEM) and atomic absorption spectroscopy (AAS) methods, respectively. It was found that, in the optimum conditions, the in-situ composite materials with Mo2MB2 as the reinforcement phases (i.e. Mo2NiB2, Mo2CoB2, or Mo2FeB2) and M3Al/M20Al3B6 intermetallic compounds as the matrix phases (i.e. Ni3Al/Ni20Al3B6, Co20Al3B6, or Fe3Al) can be synthesized by SHS method. Increasing both the B2O3/Al ratio (i.e. from 0.28 to 0.72) and MxOy/MoO3 ratio (i.e. from 0.58 to 1.5) significantly decreased the residual Al content and increased ternary boride phases in the products. It was also revealed that the microhardness values of these SHS produced alloys can reach up to 1301 ± 162 HV.