Effect of Mo content on the high temperature properties of CoCrFeNi high entropy alloys

This study explored the impact of Mo doping on CoCrFeNi-based high-entropy alloys (HEAs) with varying Mo concentrations (x = 0, 0.1, 0.2, 0.3, 0.4, 0.5 at.%) produced through spark plasma sintering (SPS). The investigation systematically examined the influence of Mo content on the properties of CoCrFeNi HEAs based on atomic ratios. The nanoindentation properties at room temperature, as well as the mechanical properties at elevated temperatures (200 °C, 400 °C, 600 °C) and corresponding microstructural characteristics, were thoroughly analyzed. The results revealed a structural transition from a single FCC phase to a combination of FCC + σ duplex phase upon Mo doping, leading to distinct mechanical behaviors in the alloys. Tensile tests, friction experiments, room temperature nanoindentation tests, and microstructural evaluations at various temperatures were conducted. The analysis concluded that the alloy containing 0.2 at.% Mo exhibited the most favorable overall mechanical properties. The Mo0.2 alloy demonstrated notable thermal stability, maintaining consistent strength and wear resistance at high temperatures. Mo0.2 is a cost-effective alternative with enhanced machinability in contrast to conventional Ni-based HEAs. This characteristic renders it a promising option for high-temperature applications that demand exceptional mechanical strength and wear resistance. These applications encompass advanced turbine components, high-pressure friction systems, pressurized gas disks, aero-engine compressor back-end blade tenons, combustion chambers, support structures, and turbine front receivers. Schematic flow diagram of alloy powder and block preparation process and friction mechanism flow diagram