Interdependence of slurry erosion wear performance and residual stress in WC-12wt%Co and WC-10wt%VC-12wt%Co HVOF coatings

Abstract

High-velocity-oxygen-fuel deposited WC-12wt%Co and WC-10wt%VC-12wt%Co hardmetal coatings are well anchored to the mild steel substrates, giving good mechanical integrity, as well as low porosity. The mechanical integrity has been investigated in terms of erosion performance and its influence on the residual stress state in the eroded regions. Wear slurry erosion tests reveal similar rates of erosion for both systems, that becomes more severe as the impact angle increases due to higher direct impact deformation normal to the surface. The 10wt%VC-12wt%Co coating renders slightly better erosion performance throughout. Stress evaluations using X-ray and neutron diffraction reveal substantial compressive residual stresses in the WC-phases for both coating compositions in their as-coated conditions. Within their erosion scars, the stresses become more compressive with erosion angle due to the increased impact component normal to the surface. It is concluded that the better wear performance of the WC-10wt%VC-12wt%Co coatings with impact angle, correlates with larger induced in-plane compressive stresses in the WC phase.