The Study of High Temperature Oxidation behavior of Different Microstructures of HVOF Thermally Sprayed Coatings

Improvement of thermally sprayed coating properties by microstructure modification has been considered as a significant solution. therefore, in this research the effect of dissolved oxygen content and post heat treatment on the formation and distribution of secondary phase particles, particularly in nano-scale in the coatings during spraying and after that were studied. ni-5 wt% al powders were sprayed by high velocity oxy-fuel (hvof) technique under two different oxygen/fuel ratios to achieve different melting states for feedstock materials. as-sprayed coatings were exposed to complementary heat treatment including heating at 1100 °c under inert atmosphere, then furnace cooling to room temperature. the as-sprayed and heat treated coatings were evaluated for high temperature performance. isothermal oxidation tests were carried out at 950 °c for 100 h. the results showed that depending on the spraying conditions and optimization of the coating microstructure, ni-based sprayed coatings with low al content could be utilized as an efficient bond coat or overlay coating.