Microstructure and wear properties of in-situ molybdenum composite coatings by plasma spraying Mo-B4C and MoO3-Al-B4C composite powders

In this work, in-situ molybdenum composite coatings were prepared by plasma spraying Mo-B4C and MoO3-AlB4C composite powders. The microstructure, microhardness and dry sliding wear resistance of the composite coatings were explored. The results show that MoB2 and beta-MoB were formed by in situ reaction between Mo and B4C. The in-situ MoB2 and beta-MoB phases improved the microhardness of the molybdenum composite coating and formed surface adsorption layer with the oxide film during friction to prevent the propagation of fatigue cracks. The coating obtained by Mo-B4C composite powders shown better tribological performance with a friction coefficient of 0.5 and a wear rate of 0.18 x 10(-3) mm(3)/(N(.)m) than that with a friction coefficient of 0.7 and a wear rate of 4.64 x 10(-3) mm(3)/(N(.)m) of the coating obtained by plasma spraying MoO3-Al-B4C composite powders. The wear mechanism of the coating obtained by plasma spraying Mo-B4C composite powders was mainly fatigue wear, accompanied by oxidation wear and abrasive wear. The wear mechanism of the coating obtained by plasma spraying MoO3-Al-B4C composite powders was mainly fatigue wear and abrasive wear.

Automated summary

In this research, in-situ molybdenum composite coatings were prepared using plasma spraying of Mo-B4C and MoO3-AlB4C composite powders. The microstructure, microhardness, and dry sliding wear resistance of the coatings were investigated. The results showed that MoB2 and beta-MoB were formed through an in-situ reaction between Mo and B4C. These phases improved the microhardness of the molybdenum composite coating and formed a surface adsorption layer with the oxide film, preventing fatigue crack propagation. The coating obtained from Mo-B4C composite powders exhibited better tribological performance compared to the coating obtained from MoO3-Al-B4C composite powders.