Effect of coating thickness on properties of Mo coatings deposited by plasma spraying

Plasma sprayed molybdenum coatings with different coating thicknesses (100, 200, 300 and 400 mm) were deposited on steel substrate. The variation in microstructural characteristics and properties of coatings with various thicknesses was investigated. The microhardness was measured using a Vickers' indenter. The quantitative investigation of porosity is carried out with the help of computerised image analyser. The influence of coating thickness on wear resistance was estimated using pin on disc wear test rig. The worn surface of coated pin was characterised by scanning electron microscopy. The experimental results indicated that porosity of coating was increased with increased coating thickness. The enhanced coating thickness also resulted in decreasing microhardness and reduced wear resistance. In this study, the plasma sprayed thin coating with thickness of 100 mm possesses the lowest porosity, the highest hardness and better wear resistance.