Micro-structural and tribological assessment of HVOF sprayed coating by Co alterations for wear applications

This paper illustrates the slurry erosion behavior by evaluating three operating process parameters, such as slurry concentration, impact velocity and impact angle of High velocity Oxy Fuel (HVOF)-sprayed WC-17Co and WC-12Co coating on substrates of AISI304 turbine steel. The experiments were structured using Taguchi L 9 design matrix on a self fabricated erosion test rig. The output parameter in terms of erosion loss is measured from thermo-gravimetric analysis. The erosion mechanism of uncoated and coated steel was further analyzed through Scanning Electron microscope (SEM) and X-ray Diffraction analysis (XRD). It has been observed that uncoated steel degraded severely due to pitting and ploughing action of the erodent particles. However erosion reduced appreciably by 53% after the application of the HVOF-sprayed WC-12Co coating and was further improved by 4% via HVOF-sprayed WC-17Co coating. Some losses on the surface of both coated steels were attributed by the presence of splat, minor ploughing and micro-chipping. Slurry concentration followed by impact velocity was acknowledged as critical parameters of the study.