Structural characteristics and wear, oxidation, hot corrosion behaviors of HVOF sprayed Cr3C2-NiCr hardmetal coatings

Abstract

It is of great importance to determine the wear, oxidation, and hot corrosion behavior of thermally sprayed Cr3C2-NiCr hardmetal coatings under different conditions, which are widely used in the different industrial applications. In this study, the influence of damage mechanisms such as oxidation, hot corrosion, and wear of Cr3C2-NiCr hardmetal coatings on stainless steel substrates at different temperatures and time periods was investigated. The properties of the coated samples were examined using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) and 3D-optical surface profilometry. Increased time at oxidation tests has indicated that different oxide formations was accelerated by the effect of temperature. It is identified that changes have occurred in the microstructure of the Cr3C2–NiCr coatings depending on high temperature and time. At the oxidation tests, the oxidation layer was increased as a function of time. As a result of the hot corrosion effect, the Na2SO4 and V2O5 powder mixtures melted with the effect of temperature, leaked from the micro cracks, pores and moved from the coating surfaces to the inner regions. The Cr2O3 structure formed as a result of the temperature effect on the coating surface showed a protective feature, increasing the resistance of the coating against oxidation and delaying the formation of damage. Findings from the wear test indicated that the relative sliding motion of the surfaces in contact with the movement of the applied load results in shear stress, which causes friction force to be generated. The friction coefficients increase depending on the load, and as the load increases, resulting in volume losses.