Improvement of microstructural and mechanical properties of plasma sprayed $\mathrm{Mo}$ coatings deposited on $\mathrm{Al}$–$\mathrm{Si}$ substrates by pre-mixing of $\mathrm{Mo}$ with $\mathrm{TiN}$ powder

The present work embodies development of a new class of mechanically improved $\mathrm{Mo}$–$\mathrm{TiN}$ coating material using plasma spray technique. The coatings are developed on $\mathrm{Al}$–$\mathrm{Si}$ alloy at different torch input power levels ranging from $15$ kW to $30$ kW. Pre-mixing of $\mathrm{TiN}$ with Molybdenum enhances adhesion strength and hardness of the coatings. Maximum adhesion strength of $22$ MPa ($\pm0.75$) and hardness of $748$ Hv ($\pm30$) are found for the coating when molybdenum is pre-mixed with $10\%$ $\mathrm{TiN}$. FESEM micrographs of the as-sprayed coatings showed formation of plate-like structures of splats which indicates $\mathrm{TiN}$ sites as reinforcement in Mo matrix. X-ray diffraction study reveals the formation of both $\mathrm{MoO}_2$ and $\mathrm{TiN}$ as minor phases in the coating microstructure. The significant enhancement of mechanical properties like adhesion strength and hardness is attributed towards the presence of these phases.