Creep behaviour prediction and optimum design of plasma sprayed coatings with intermediate bonding layer

The surface enhancement of conventional constructive materials through plasma sprayed coatings is a well-established practice. This flexible and relatively economically efficient method enhances the properties of machine elements that are designed for demanding purposes. The deposition strategy and the corresponding applied conditions have a strong impact on the occurring technological and mechanical coating properties, which may be variable when they are exposed beyond certain critical loads due to their porosity and to a herewith activated creep phenomenon. In former investigations, single layer plasma spray coatings were examined and their creep behaviour was quantified with the aid of an impact tester. In the present paper, the creep behaviour of two-layer coatings consisting of an intermediate bonding layer and a superficial one with different material specifications, both produced by the plasma spray method, is described with the aid of experimental and analytical investigations. Considering the mechanical and creep properties of the individual coating layers, through a FEM supported simulation of the material deformation during the impact test, the creep behaviour of the entire structure of two-layer coatings is determined. In this way, the thickness of the individual coating layers to avoid creep can be optimized, thereby improving the overall coating performance under load. Materials used: st-70 steel(substrate).