Single asperity scratch behaviour of cast stellite 6 alloy

Abstract

The aim of this paper is to investigate the nano-scale sliding wear behaviour of cast Stellite 6 (Co-28Cr-4.5W-1C) with a view to comprehend single asperity deformation. A nanoindentation system (NanoTestTM—Micro Materials Limited, UK) equipped with wear testing module was used to simulate single asperity deformation behaviour using a sphero-conical indenter of 10μm tip radius, 60◦ included angle for a sliding distance of 60μmunder 50 and 100mNload, with sliding velocity of 2μm/s. The test load was increased linearly over the sliding distance. Post-test evaluations included X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM) measurements to determine the failure mode and wear volume. An elastic-plastic finite element model (FEM) was used to compare the displaced volume of alloy with the experimental data. There is limited work available to understand the nanotribological properties of Stellite alloys in published literature. In the current investigation results are discussed in terms of microstructural and tribo-mechanical evaluations to provide an understanding of the structureproperty relationships. Results indicate that the wear behaviour at the nano-scale was dominated by the interaction of interdentritic carbides and metal matrix. It can be concluded that nano-scale sliding wear behaviour of cast Stellite 6 alloy is controlled by single asperity deformation. The predictions of nano-scale elastic-plastic FEM to calculate the volume displaced by the scratch are also discussed.