Composite, Effective, and Real Hardnesses of Thin Coatings

摘要

The paper presents the results of an analysis of the mechanics of contact between a rigid sphere and an elastic rigidly plastic two-layer half-space that imitates a surface covered with a hard strengthening coating. Analytical dependences are derived which relate the surface hardness to the base and coating hardnesses within the whole possible range of the coating thickness. Analytical dependences that relate the surface hardness to the coating thickness and the indentation depth of a hard tetragonal pyramid are also obtained. A new physical interpretation of the mechanism of the deformation of a layered solid is proposed for the range of the indentation depth that commonly characterizes the domain of the existence of the composite hardness. The term "real coating hardness" is specified and a new term "effective hardness of the coating material" is proposed. The obtained theoretical solutions are used to determine the ranges of the thicknesses within which the composite and effective hardnesses of a hardened surface exist.