A New Method of Preparing In situ Synthesized Titanium Oxide Coatings by Very Low-pressure Reactive Plasma Spraying

Very low-pressure reactive plasma spraying (VLP-RPS) was applied to in situ synthesized composite titanium oxide coatings at different spraying distances, with titanium powder and oxygen injected into the high-temperature plasma jet. The resulting coatings contained mixed phases of TiO2, Ti2O3, and Ti2O, and possessed dense and layered microstructures. As the spraying distance increased from 400 to 900 mm, the oxidation of the titanium powder was more complete, and the mass fraction of the TiO2 phase in the coating increased from 12.4 to 38.6%. At the same time, the porosity of the coating correspondingly increased from 0.70 to 2.40%. Meanwhile, the average hardness of the titanium oxide coatings varied from 8.7 to 10.2 GPa, which was higher than that of TiO2 coating (8 GPa or so) prepared by other traditional spraying methods.