Comparison of Dry Sliding Tribological Behavior of Nanostructured Al₂O₃–13 wt% TiO₂ Coatings Prepared by High-Efficiency Supersonic Plasma Spraying and Atmospheric Plasma Spraying

Plasma-sprayed ceramic coatings have been widely used in friction and wear protection of mechanical parts. In this paper, the nanostructured Al₂O₃–13 wt% TiO₂ coatings were prepared by high-efficiency supersonic plasma spraying (HESP) and atmospheric plasma spraying (APS), respectively. The surface and section morphology of the coatings were observed by scanning electron microscopy (SEM). The phase composition of the coatings was analyzed by X-ray diffraction (XRD). The dry sliding friction properties of the coatings were tested on UMT-3 friction and wear testing machine. The results show that after plasma spraying, a large amount of γ-Al₂O₃ phase appears, while the TiO₂ phase almost disappears in the coatings; compared with APS, the coatings sprayed by HESP have fewer defects and better coating quality; under dry friction condition, the steady-state friction coefficient of the coatings sprayed by HESP and APS all decreases with the increase of load, and the wear volume all increases with the increase of load. When the load is more than 40 N, wear volume of the coatings sprayed by APS is basically twice that of HESP; the wear mechanism of the coatings sprayed by HESP is the laminar cracking, peeling off and the adhesive wear.