Contact fatigue crack growth in PVD-coated spur gears

The aim of this work is to investigate the (rolling) contact fatigue behaviour of transmission spur gears coated with PVD (Physical Vapour deposition) thin hard films. Numerical models of coated steel and titanium spur gears were developed. The effect of the residual stress gradient induced by the coating deposition process was considered in the calculations. A theoretical-numerical procedure was arranged to foresee the crack propagation direction. Such a procedure could represent a powerful tool to predict the (rolling) contact fatigue resistance of PVD-coated gears.