WEAR BEHAVIOUR OF HVOF SPRAYED WC-Co COATED STEEL

Abstract

Advances in power generation technology have resulted in increasing demand for materials that can work at extremely high temperature under severe conditions of erosion and corrosion. Although some steels and superalloys posses adequate strength at high temperatures, they but often lack in wear resistance. Erosion due to solid particle is a major problem in the power plant industry which runs on hydro & steam turbines. Heavy damages of under water parts in hydro electric projects due to hard silt particles are responsible for serious erosion problems. To prevent this damage there are many grades of steels developed. No alloy is immune to erosion corrosion mode of degradation. Even the superalloy degrades due to this mode of attack if they are used continuously for longer period of time therefore the boiler tubes can be protected by applying coatings which provide the requisite resistance to erosion corrosion whereas the alloy provide the necessary mechanical strength. The present work examines boiler steel T-22 substrate (sample size 25X25X5mm), after coating by WC-Co using HVOF technique, for erosion test on "Air jet impact erosion tester". The various impact angles like 300, 600 and 900 have been used to see the relative degree of wear. Alumina oxide was used as erodent material which was fed into the tester after proper treatment. The samples have been examined by SEM/EDAX to ascertain the mechanism of erosion.