Corrosion resistance of stainless steel coatings elaborated by solar cladding process

The resistance to corrosion of stainless steel coatings deposited onto carbon steel substrate with a solar processing is analyzed. The solar cladding consists in melting the powder of stainless steel AISI 316 under a beam of concentrated solar energy, followed by a rapid solidification. A continuous scanning process is performed by moving the specimen at controlled speed, according to the solar direct normal irradiation. The solar processing is carried out in a small scale solar furnace of CNRS at Odeillo, France. The experiments are carried out in vacuum, under an average flux density of 13400 kW/m2. Various laws of velocity are used: 0.8 mm/s, 1.6 mm/s and 1.8 mm/s. Strips 55 mm in length and 6 mm in width of dense solid layer are obtained. The adhesion at the interface between the coating and the substrate is correct. The research work focuses on the characterization of the layer with respect to the operating parameters. The distribution of composition within the layers is observed with EDX analysis. In all cases Cr and Ni contents are lower than those of the initial powder (17% Cr and 12% Ni). Using high velocity scanning process yields to dendritic austenitic microstructure observed by optic microscopy and by SEM. The corrosion behaviour is analyzed using anodic polarization test in a 0.6 M NaCl solution. A passive layer is formed, thus offering a very good resistance to corrosion.