Influence of Heat Treatment on Microstructure and Properties of High-Velocity Arc-Sprayed Fe-Based-Al₂O₃-B₄C Coating

To prolong the longevity of rotary blades, Fe-based-Al₂O₃-B₄C coatings were prepared on 65Mn substrate using high-velocity arc spraying technology. The coatings were subsequently heat-treated at 350, 450, 550, 650, and 750 °C for 2 hours. The effect of heat treatment temperatures on the microstructure, phase composition, microhardness, tensile bonding strength, and wear resistance of Fe-based-Al₂O₃-B₄C coatings was studied by scanning electron microscope, x-ray diffractometer, Vickers microhardness tester, tensile tester, and friction wear tester, respectively. The results showed that with the increase in heat treatment temperature, the porosity of the coating gradually decreased while the compactness of the coating increased. At 650 °C, the tensile bonding strength of the coating was the highest at 35.6 ± 3.5 MPa, which was 1.2 times higher than that of the as-sprayed coating. When the coating crystallized at 550 °C, the average microhardness and Weibull modulus reached the peak values of 1508 ± 171 HV_0.1 and 23.8, respectively. The wear resistance of the heat-treated coating was the best at 550 °C, the wear rate reached a minimum of (8.2 ± 0.7) ×10⁻⁶ mm³N⁻¹m⁻¹, which was 0.6 times lower than that of the as-sprayed coating. The main wear mechanism was adhesive wear and abrasive wear.