Microstructure, Mechanical Properties, and Corrosion Resistance of NiAl-CoCrFeMo High-Entropy Alloys by Controlling Mo Co-Doping

In this work, two alloys of Ni35Al30(FeCo)25Cr10-xMox (x = 0, 5) were prepared via the vacuum arc melting method, and the effects of Mo on the microstructure, mechanical properties, and friction and wear properties of the alloys were investigated. The addition of Mo improved the mechanical properties, wear resistance, and corrosion resistance of the alloy system. With the addition of trace amounts of Mo, the precipitate phase of the alloys transformed from spherical to acicular and plate-like. The precipitated phases in a co-lattice relationship with the matrix allow for a substantial increase in the strength of the alloy at both room and elevated temperatures without a significant loss of plasticity. Ni35Al30(FeCo)25Cr5Mo5 has excellent mechanical properties, with a hardness of 558.2 HV; a yield strength of 1320 MPa at 600 °C; and a yield strength of 537 MPa at 850 °C. As the temperature increased, the wear mechanism changed from abrasive wear to adhesive wear. At 600 °C, Ni35Al30(FeCo)25Cr5Mo5 had the lowest wear rate of 1.78 × 10−5 (mm3/Nm). The precipitated phases, which have high hardness and maintain a conformal interface with the matrix, play an important role in slowing delamination wear, keeping the wear rate of this alloy low at both room and high temperatures. Electrochemical experiments on the two alloys at room temperature revealed that Ni35Al30(FeCo)25Cr5Mo5 exhibited excellent resistance to pitting, with a pitting potential of 0.016 V.