The Local Yield Map of Hard Coating under Sliding Contact

The stress distribution in the hard coating and substrate under elastic sliding contact is analyzed with the finite element method. The elliptical distribution of normal contact pressure is supposed and the combinations of coating thickness, friction coefficient and elastic modulus of coating and substrate are changed in wide range. The position of yield initiation is found with the calculated result and the local yield map is introduced in relation to the ratio of the coating yield strength to substrate yield strength and the ratio of the coating thickness to the half-contact width. The local yield map shows that the yield at the coating interface is the most general case in wide range of contact condition and the yield at the coating surface becomes the next general case as the friction coefficient becomes large.