The effect of thin hard coatings on the Hertzian stress field

In this paper the effect of thin rigid coatings on the stress field generated by a Spherical indentation on a flat halfspace is investigated using a finite-element program. It is shown that thin hard coatings can have a significant effect on the radial and circumferential stresses. Of particular interest is the reduction in the maximum (radial) tensile stresses, since this indicates that hard coatings can be used to protect brittle materials against elastic contact damage. The stress reduction increases with the Young's modulus and thickness of the coating. The reduction in the substrate stresses is, however, accompanied by an increase in the maximum tensile stresses in the coating itself.