Mechanical performance and residual stress of WC-Co coatings manufactured by Kinetic Metallization™

Abstract Electrolytic hard chrome (EHC) plating is a source of environmental pollution due to evolution of hexavalent chromium, which is a known carcinogen. Coating technology known as Kinetic Metallization™ (KM™) is an alternative to EHC for depositing wear resistant WC-Co coatings. Kinetic Metallization™ employs high kinetic energy of impacted feedstock particles and achieves a dense coating with good intersplat bonding. However, the high kinetic energy imparts peening and thermal stresses that are different from other thermal spray processes. This work characterizes the residual stress profile and room temperature wear behaviour of WC-Co coatings deposited under several input parameters. A combination of SEM imaging and etched optical micrographs revealed significant plastic deformation and particle penetration at the interface due to high energy impact of feedstock particles. No signs of substrate grain refinement were detected. The coating was composed primarily of WC and Co with minor compositional variations, as calculated by quantitative Rietveld analysis, with respect to the input parameters. Coating residual stresses were compressive in nature due to domination of thermal contraction stresses over peening stresses. The wear resistance assessed by the pin-on-disk method revealed a wear performance equivalent to conventionally sprayed WC-Co coatings.