Hertzian contact response of single-layer, functionally graded and sandwich coatings

The distributions of surface and subsurface stresses within single-layer, functionally graded and sandwich coatings on monolithic substrates under Hertz contact conditions (i.e., cylinder on flat contact geometry) have been analyzed by finite element method. The effect of the ratio of coating thickness to contact radius (t/a) on the distributions and magnitudes of contact stresses within coating and at coating/substrate interface was obtained by single-layer coating systems. With increasing the coating thickness, the depth of maximum shear stress was moved away from the substrate/coating interface. Compared to the single-layer coating, the maximum shear stress and Von Mises stress within the functionally graded coating or sandwich coating are relatively low. The studies in this paper can provide some insights regarding the design of the hard coatings in most tribological applications.