Three-Dimensional Finite Element Analysis Of Crack Of TiN Coating

Wear-resisting coatings is widely applied to the contacted surfaces of many machines, which can improve the capability of resisting frictional wear on the local contact areas and prolong the work-life. However, during the process of manufacture there must be some flaws inevitably within the interfaces or coatings, where it is easy to form the critical cracks, make coatings failure and peeled off under the rolling and sliding contact. So it is very important to study the stress distributions of coating-substrate, the mechanism of crack initiation and development, and the fracture intensity of cracks.The two and three dimensional elastic-plastic friction contact problems of a TiN coating under the indenting by an elastic sphere and the sliding by a cylinder, respectively, are studied by use of the finite element methods. The stress distribution of the coating-substrate is calculated at first, and then the crack initiation, shape and location are discussed. At last the fracture intensity, J integral, of some cracks on the surface and interface are calculated. The influence of the thickness of coating and friction coefficients are analyzed. Some important results are as follows. (1) Under the indenting the largest stretch stress occurs near the contact edge of the coatings surface;under the sliding, there occure cracks perpendicular to the sliding direction on the surface. (2) When the coating is thiner it is ease to initiate the surface cracks, but the coatings become thicker, the interface cracks will be introduced. (3) The surface and interface cracks are ease to be introduced for higher friction coefficient. (4) The influence of the parameters on j-integral value, which contains the thickness of coating, substrate material, shape of crack and obliquity of crack, are distinct. When the substrate is Hss, j-integral value of crack on the interface is larger. When the substrate isWC-Co, j-integral value of crack on the surface is larger.