Engineering HVOF-Sprayed Cr3C2-NiCr Coatings: The Effect of Particle Morphology and Spraying Parameters on the Microstructure, Properties and High Temperature Wear Performance

Chromium carbide-based thermally sprayed coatings are widely used for high temperature wear applications.  In these extreme environments at those temperatures, several phenomena will degrade, oxidize and change the microstructure of the coatings, thereby affecting their wear behaviour.  Although it can be easily conceived that the Cr₃C₂-NiCr coating microstructure evolved after high temperature exposure will depend on the as-sprayed microstructure and spraying parameters, very little has been done in this regard. This study intends to develop a better understanding of the effect of spraying parameters on the resulting chromium carbide coating microstructure after high temperature operation and high temperature sliding wear properties. The microstructures of different coatings produced from two morphologies of Cr₃C₂-NiCr powders and under a window of in-flight particle temperature and velocity values were characterized through X-ray diffraction (XRD) and scanning electron microscopy (SEM).  Sliding wear at 800°C was performed and the wear behaviour correlated to the spraying parameters and coating microstructure.  Microhardness and elastic modulus values of the coatings before and after sliding wear was also measured.