Tribological Properties of WC-Co/NiCrBSi and Mo/NiCrBSi Plasma Spray Coatings under Boundary Lubrication Conditions

The tungsten carbide based WC-Co/NiCrBSi (50/50) and molybdenum based Mo/NiCrBSi (75/25) coatings were investigated under boundary lubricated sliding conditions, and their tribological properties were analysed and compared. These two coatings are in service for a long time, but there are very few papers dealing with their tribological properties, especially in lubricated sliding conditions. The NiCrBSi self-fluxing alloy is one of the popularly used materials for thermal sprayed coating, with relatively high hardness, reasonable wear resistance and high temperature corrosion. Tungsten carbide (WC) is one of the most widely used commercial hard coating materials, and is added to the NiCrBSi coating to improve its hardness and wear resistance. Molybdenum (Mo) is added to the NiCrBSi coating to reduce its coefficient of friction, i.e. to improve its dry sliding wear resistance. The results showed that WC-Co/NiCrBSi coating was more wear resistant, but caused higher wear of the counter-body material. Coefficients of friction were similar for both coatings.