Microstructures, mechanical properties and tribological behaviors of HVOF-sprayed CoMoCrSi alloy coatings before and after 800 °C-annealed treatment

The microstructures, mechanical properties and tribological behaviors in a wide temperature range of high velocity oxygen fuel sprayed CoMoCrSi coatings before and after 800 °C-annealed treatment were comparatively investigated. Particularly, the annealed CoMoCrSi coatings registered well crystallization, improved microstructures and enhanced properties compared to the as-sprayed coatings. Specially, the surface microhardness increased by 13.3%, and the adhesive strength increased by 12.5% after the annealed treatment. Moreover, a compact oxides layer comprising Cr₂O₃, Co₃O₄, MoO₃ and CoMoO₄ formed on the annealed coating surface, which could be account for the increased microhardness and excellent tribological behaviors of the annealed coatings. The annealed coatings registered lower friction coefficients and wear rates than the as-sprayed coatings in a wide temperature range. Consequently, the 800 °C-annealed treatment could significantly improve the microstructures and properties of the HVOF-sprayed CoMoCrSi coatings. Moreover, the annealed CoMoCrSi coatings could be a well candidate for the abrasion-resistant material in a wide temperature range.