Molybdenum based amorphous and nanocrystalline coatings prepared by high velocity oxy-fuel spraying

Abstract

The high velocity oxy-fuel (HVOF) based thermal spray process has developed as a potential advantageous approach for fabricating various kinds of functional coatings. In this article, the coatings of Mo-based alloy were synthesized using the HVOF process. The microstructure and the mechanical properties of the HVOF-processed coatings were investigated using SEM, TEM, XRD, and hardness and wear tests. Annealing treatment was applied to the as-sprayed coatings to develop the microstructure and its effect on the microstructure and mechanical properties of the coatings was examined. It is found that the HVOF-processed Mo-based alloy coatings are comprised of an amorphous splat matrix embedded with nano-sized crystalline particles. Annealing at temperatures over 950 °C results into crystallization of the amorphous matrix. The mechanical properties of the as-sprayed coatings are enhanced with annealing temperature up to 750 °C and from 950 to 1050 °C, keeps constant between 750 and 950 °C, and reduce over 1050 °C. The change of the mechanical property with the microstructure was illustrated in the study.