Tribological Behaviour of Thermally Sprayed Coatings: A Review

Abstract

Coatings are used for modifying the surface properties of critical components subjected to mechanisms such as corrosion, oxidation, wear, or under an excessive heat load failure. Selection of the coating material and method of depositions are very important for any application. Coatings are effectively and economically used to guard the substrate surface from wear also to reduce friction. The tribological response of a coating system depends on many factors like coating properties, counterpart, substrate, interface, and running conditions. Hence, selection of the appropriate coating for a given tribological application is difficult. Thermally sprayed WC and CrC based cermet coatings are extensively used in the hydro turbine for resistance to wear like abrasive, erosive and cavitation. The NiCrAlY coating showed better resistance to high-temperature oxidation and corrosion due to the formation of protective oxides. At high temperature working environment and chemically aggressive condition NiCrSiBC alloy reveals a good balance between corrosion and wear resistance. The NiCrBSi coating showed a good surface finish as well as the bonding interface. This paper presented the review related to the selection of coating powder and process of protective wear resistance coating by thermal spray techniques. The effect of spraying techniques and spraying parameters on the performance of the coating is different for every coating. The wear types, powders, Plasma spray and HVOF spray methods are discussed to identify the coating for a specific application.