Investigation of the Effects of Spark Plasma Sintering Parameters on Equiatomic CoCrFeNiMo High Entropy Alloy

In this study, the effects of sintering temperatures and pressures on densification, crystalline phases, microstructural characterization and mechanical properties of mechanical alloyed equimolar CoCrFeNiMo HEA were investigated. The alloy was composed of major BCC and minor FCC solid solutions coexisting after 40 h of milling. Increasing milling time caused to increase in lattice strain and a decrease in crystallite size. Furthermore, sintering temperature and pressure resulted in the decomposition of the BCC metastable phase and the formation of intermetallic phases and the FCC phase. Herein, increasing sintering temperature and pressure led to decrease lattice strain and increase crystallite size. Moreover, sintering temperature and pressure caused to formation of new intermetallic phases in HEA2 and HEA3. Results revealed that increasing sintering temperatures and pressures of equimolar CoCrFeNiMo end up with a reduction of large pore, enhancement of density value from 7.53 ± 0.02 to 8.78 ± 0.005 g/cm³, hardness from 3.915 to 8.316 GPa, and increment of wear rate from 21.8 × 10⁻⁷ to 57.6 × 10⁻⁷ mm³/Nm.