Electrochemical corrosion study of Inconel 625 laser coatings by wire and powder feedstock

Abstract

The corrosion performance of Inconel 625 coatings is mainly influenced by the amount of Fe composition and degree of microstructural heterogeneities. Reducing the Fe dilution and microstructural modification during laser cladding process are challenges to overcome. In this work, the dilution analysis and corrosion performance, in de-aerated 3.5% NaCl solution, of Inconel 625 wire and powder laser coatings deposited under similar conditions was carried out. The microstructural investigation of the top surfaces of the coatings before and after the corrosion test was conducted using a scanning electron microscopy combined with energy dispersive spectrometer. It was found that the Fe dilution is significantly lower (1.4%) in the wire coating compared with the corresponding powder coating (12.6%). This is the reason for higher amount of interdendritic precipitates (i.e., microstructural changes) in the powder coatings. Due to these changes, the powder coating exhibited lower resistance to corrosion as compared with the wire coating.