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 wea r applications in the aircraft, automotive and paper industries. High-cycle fatigue tests were performed at room temperature and 370 degrees C on SAE 12L14 low-carbon steel and aluminium alloy 2024-T4 thermally sprayed with W C-17 wt% Co using the high-velocity oxygen fuel process. The fatigue life d istributions of specimens in the polished, grit-blasted, peened and coated conditions are presented as a function of the probability of failure. Compo site beam theory was applied to the coated beam to evaluate the stresses an d elastic modulus. The stress-strain curves for the coated and uncoated spe cimens were used to evaluate the stiffness factor for the aluminium alloy a nd steel. It is concluded that (i) the coated specimens exhibited significa ntly high fatigue lives com pa red with the uncoated specimens, (ii) the me chanisms of deformation for the coated and uncoated aluminium alloy specime ns are quite different and (iii) the elastic modulus of the coating plays a significant role in determining the fatigue strength of the coated compone nt. (C) 1998 Kluwer Academic Publishers.