Micro-chemical investigation of thick W coating on AISI 420 martensitic steel

W is a favorable material for protecting mechanical components such as thermal shields and divertor parts from plasma damage in nuclear fusion reactors. A W thick coating has been developed on AISI 420 martensitic stainless steel substrate by means of plasma spray technique. Plasma spraying has been used for its simplicity, the possibility to cover complex and extended surfaces and the relatively low cost. An appropriate interlayer has been optimized to increase the adhesion of W coating on the steel substrate and to provide a soft interface with intermediate thermal expansion coefficient for better thermo-mechanical compatibility. The present work describes and discusses the results of micro-chemical investigations on coating and interface by X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES).