Papers by Author: Kun Zhang

Abstract: The evaluation of the interfacial adhesion of coating system has always been a rough task. In this paper, a special testing method of cross-sectional indentation is applied on a model coating system, i.e. electroplated chromium on a steel substrate which is generally regarded as an example of materials pair with strong adhesion. Based on fractography analysis with SEM and interfacial stress simulation with FEM, it is found that interfacial shear stress may induce coating spalling. More interestingly, spalling location is sensitive to substrate pretreatment process. This shows the feasibility of cross-sectional indentation to distinguish interfacial strength at a high level.

Abstract: novel duplex coating is presented on steel substrate by laser discrete quenching prior to chromium coating deposition. Due to the periodical changes in the mesostructures and properties of underlying substrate, the cracking and spalling behaviors of the duplex coating are expected to be different from that of conventional coating. A classic erosion experiment is selected to characterize the positive response of the duplex coating subjected to thermal loads. It is found that the surface cracking is partly restrained and the interface cracking is partly arrested. FEM modeling results show that a unique stress state is induced in the duplex coating with the tempering of the discrete pre-quenched regions due to thermal loading, which is believed to be the mechanism of controlling the damage modes.