What is power plant metallography and what does this job do?

Metallography generally refers to the structural types of metallic materials, such as graupel, austenite and martensite. For details, please refer to metallography, which belongs to the field of materials science. I don't know why the metallographic situation of the power plant is specific. Estimation is used to consider the internal metallographic changes of the corresponding conductive materials under what current, so as to decide whether it is reasonable or not and whether it needs to be replaced.