The effect of high-velocity oxygen fuel, thermally sprayed WC-Co coatings on the high-cycle fatigue of aluminium alloy and steel

Thermally sprayed WC Co coatings are currently used in numerous contact wear applications in the aircraft, automotive and paper industries. High-cycle fatigue tests were performed at room temperature and 370°C on SAE 12L14 low-carbon steel and aluminium alloy 2024-T4 thermally sprayed with WC-17 wt% Co using the high-velocity oxygen fuel process. The fatigue life distributions of specimens in the polished, grit-blasted, peened and coated conditions are presented as a function of the probability of failure. Composite beam theory was applied to the coated beam to evaluate the stresses and elastic modulus. The stress strain curves for the coated and uncoated specimens were used to evaluate the stiffness factor for the aluminium alloy and steel. It is concluded that (i) the coated specimens exhibited significantly high fatigue lives compared with the uncoated specimens, (ii) the mechanisms of deformation for the coated and uncoated aluminium alloy specimens are quite different and (iii) the elastic modulus of the coating plays a significant role in determining the fatigue strength of the coated component