Effect of grinding on surface characteristics of HVOF-sprayed WC–10Co–4Cr coatings

Abstract

The aim of this research was to investigate the effect of the grinding depth of cut on surface quality and corrosion behaviour of WC-10Co-4Cr cermet coatings. Accordingly, a WC-10Co-4Cr coating with 400 μm thickness was deposited on the carbon steel substrate using a High-Velocity Oxygen Fuel (HVOF) process. Consequently, the effect of different depths of cut on the coating properties was evaluated. Porosity, surface roughness and microhardness of as-sprayed and ground coatings were measured in order to investigate the effect of grinding on the coating characteristics. The corrosion behaviour of the coatings was evaluated using open circuit potential, electrochemical impedance spectroscopy, and potentiodynamic polarisation tests. The results indicated that after grinding, the porosity and microhardness of the coatings were increased and the surface roughness was decreased. Furthermore, the increase in the depth of cut increased the coating porosity and microcracks. Therefore, the corrosion resistance of the coating was decreased.

Enhanced mechanical properties of molybdenum-coated aluminium via laser cladding

“…In the process of HVOF spraying, the feedstock Mo powders are first heated up to a molten or semi-molten state, then accelerated and impacted onto the Al substrate with a relatively low temperature and high velocity and finally solidified in the form of lamellar ‘splat’ due to the deformation of the droplet [18,19]. Since millions of Mo powder particles are heated up simultaneously as well as the Mo element has a high melting point (2896 K [20]), some Mo powder particles may not be melted adequately, resulting in the trapped unmelted particles in the coating.…”

Effect of Combined Grinding–Burnishing Process on Surface Integrity, Tribological, and Corrosion Performance of Laser‐Clad Stellite 21 Alloys

“…[ 27 ] It is evident that only grinding is not adequate to address the porosity issues, as the grinding often causes further microcracks and dislodgement of hard particles from the binding matrix materials. [ 7 ] Therefore, the combined grinding–burnishing would easily be applied to eliminate/minimize the surface microporosity.…”

“…[6] As a finishing process, grinding has also been attempted to improve surface integrity of various hard coatings. [7,8] While the grinding increases hardness, it can deteriorate surface topography by increasing microcracks due to the co-existence of brittle fracture and ductile flow, which consequently compromises corrosion and fatigue resistance. Grinding often results in microporosity within the subsurface of deposited hard coating due to thermal heating and cooling cycles.…”

Geometric Influence of Hard Phase on Corrosion Performance between WC-Reinforced Coatings Prepared by High-Velocity Oxygen-Fuel Spray and Electric Contact Strengthening

“…The corrosion resistance can even be influenced by artificially changing the surface morphology. Pishva et al [14] reported the porosity and microcracks of HVOF-sprayed WC-10Co-4Cr coating were increased by mechanical grinding. This made it possible for corrosive solution to penetrate into the coating, leading to a decrease in the corrosion resistance of the coating.…”