On the Problem of Wear Resistant Coatings Separation From Tools and Machine Elements

The article considers separation of wear resistant coatings of tool and engineering materials which arises both during coating fabrication and use of the product. The cause of this phenomenon is assumed to be related to thermal residual stresses generating on the coating-substrate border. These stresses have been analyzed and methods are provided to calculate it after produced composite material is cooled down from the temperature of coating synthesis to the ambient temperature. A no-fracture condition has been stated in relation to coating-substrate thicknesses, temperature differences and physical and mechanical properties of combined materials. The issue of intermediate layer incorporation with pre-set parameters has been discussed. A co-effect of thermal residual and functional stresses on the strength of the boundary layer has been considered when heating, tension and compression of a product with wear resistant coating. Conclusions have been made, as well as recommendations to improve fracture strength of products with thin wear resistant coatings.