Non-Steady Wear of a Two-Layer Coating Taking into Account Frictional Heating

The application of two-layer coatings is one of the most widely used ways to increase the performance capacity of heavily loaded frictional joints. Design of two-layer coatings for dry sliding friction surfaces and prediction of their efficiency involve the need to develop mathematical models of sliding contact allowing for wear and frictional heating. To achieve this goal, we consider a nonsteady quasi-static contact problem of uncoupled thermoelasticity of a rigid punch in the form of half-plane sliding with a constant velocity over the surface of a two-layer elastic coating bonded on its bottom face to a flat rigid substrate. During the sliding, the punch also penetrates into the two-layer coating in a direction normal to its surface. The punch friction against the coating surface is mathematically described by the Coulomb friction model. The heat flow generated by friction is directed into the coating depth. The frictional sliding contact gives rise to wear of the two-layer coating. The stated problem is solved using the Laplace integral transform. The basic characteristics of each layer, namely, displacements, temperature, and stresses, are presented in the form of the contour integrals of meromorphic functions. The analysis of the properties of the integrand poles in the complex plane of integration and determination of thermoelastic instability domains in the space of problem parameters are followed by evaluation of the contour integrals. The influence of the problem parameters on the sliding contact main characteristics, i.e., temperature, wear, and stresses, is studied. As an example, the wear of a two-layer coating with its upper layer made of titanium nitride and lower layer made of titanium (TiN/Ti) is considered. The numerical results show that by properly selecting the coating layer thicknesses, better wear resistance and lower contact temperature of the coating can be achieved.