Improvement of microstructural and mechanical properties of plasma sprayed Mo coatings deposited on Al-Si substrates by pre-mixing of Mo with TiN powder

The present work embodies development of a new class of mechanically improved Mo-TiN coating material using plasma spray technique. The coatings are developed on Al-Si alloy at different torch input power levels ranging from 15 kW to 30 kW. Pre-mixing of TiN with molybdenum enhances adhesion strength and hardness of the coatings. Maximum adhesion strength of 22 MPa (+/- 0.75) and hardness of 748 HV (+/- 30) are found for the coating when molybdenum is pre-mixed with 10% TiN. FESEM micrographs of the as-sprayed coatings showed formation of plate-like structures of splats which indicates TiN sites as reinforcement in Mo matrix. X-ray diffraction study reveals the formation of both MoO2 and 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.