ABSTRACT
Chemical or electrochemical etching is usually necessary to reveal the microstructural features of superalloys. Sample preparation requires a certain degree of skill and experience, due to the high chemical resistance of most superalloys. In the case of electron microscopy, since the differences in composition between the matrix and γ’ phases are relatively small, the contrast in absorbed or backscattered electron images is only slight, and it is often necessary to lightly etch specimens before examination. Two etchants which can be used to reveal the γ’ particles in single crystal superalloys are given in Table 3.1-1. In order to reveal grain boundaries or carbides, it is possible to use similar etchants as for steel.
