SOME TRIBOLOGICAL STUDIES ON THERMALLY SPRAYED NANOSTRUCTURED WEAR RESISTANT COATINGS

Abstract

Thermal spraying is a popular method of depositing coatings which has been used to enhance the product lifetimes under severe temperature, environmental and wear conditions. WC-Co cermets have been used traditionally as wear resistant materials. In applications where corrosion resistance is also required in addition to wear resistance, WC—lOCo--4Cr is the preferred coating composition. Today new materials with enhanced mechanical properties like toughness, hardness, wear resistance and corrosion resistance are the demands of industries. And all these can be collectively seen in nanostructured materials which are now widely used for thermally sprayed coatings. One of the commonly used materials is nanostructured cermets with all good mechanical properties. Recent work has shown that nanostructured cermets offer improved properties over their conventional counterparts. The objective of this study is to explore the wear behavior WC-lOCo-4Cr coating which has gained industrial acceptance for diverse applications. The performance of both conventional and nanostructured material in the form of coatings deposited by HVOF thermal spraying under identical conditions are investigated. The microstructure and chemical compositions of the phases in the feedstock powder and coatings are characterized by means of the FE-SEM and XRD techi iques. Image analysis is used for the evaluation of the porosity of the coatings. Indentation tests are carried out on the cross-sections of the coatings to evaluate the hardness. Wear studies like cavitation erosion testing, solid particle erosion testing and adhesive wear testing are conducted. Nanostructured coatings exhibit better resistance over the conventional coatings in all the three tests.