Effect of auxiliary gas flow parameters on microstructure and properties of Mo coatings prepared by high-energy plasma spraying

Abstract

Based on the high-power and high-flow mode of the three-cathode high-energy plasma spray system, Mo coatings were prepared on the surface of 15-5PH steel, and the effects of different auxiliary gas (helium) flow parameters on the micro-morphology and properties of the coating were studied. X-ray diffraction (XRD), scanning electron microscope (SEM), micro-hardness tester, universal testing machine, and friction and wear testing machine were used to characterize the phase composition, micro-morphology, micro-hardness, combining strength and tribological properties of the coating. The results showed that the surface of the Mo coating prepared by high-energy plasma spraying had visible pit shapes. The coating porosity gradually decreased along with the thickness of the coating, showing a typical tamping morphology. Due to the breakneck flying speed and deposition speed of powder particles, no apparent oxidation phenomenon was observed in the coating. With the increase of auxiliary gas flow, the tamping effect of the powder particles on the coating increased, and the density, hardness, and bonding strength of the coating increased. With the increase of auxiliary gas flow, the wear rate of the coating decreased, and the wear mechanism of the coating gradually changed from abrasive wear to adhesive wear.