Preparation of cross sections of thermal spray coatings for TEM investigation

A technique for the preparation of cross sections for transmission electron microscopy (TEM) of thermal spray coatings has been developed. The procedure is designed to minimize specimen damage during mechanical thinning and to reduce the effect of differential thinning during ion milling. Specimens were made by two different coating systems— WC- Co coating produced by the FARE Gun process on a mild steel substrate and Tribaloy T- 800 sprayed by the HVOF process on a nickel- base superalloy. These specimens have large areas that are electron transparent on either side of the interface, and the results have shown the atomic scale microstructure of the interface between the thermal spray coating and the substrate.