Corrosion wear response of S phase coated 316L

Abstract

S phase is a metastable nitrogen supersaturated fcc phase which, when applied as a coating using reactive magnetron sputtering, can significantly improve the corrosion wear resistance of austenitic stainless steels. Coatings with nitrogen ranges between 0.3 and 44 at.-%N were analysed and tested for hardness, modulus and fracture resistance. Duplex bcc + fcc coatings decreased in hardness with increasing N content, whereas the hardness of monophase S phase coatings increased, reaching a maximum of ~20 GPa at 28-32 at.-%N. Three types of corrosion wear process affect S phase coated 316L: first, removal of the passive film during sliding contact, second, galvanic attack of the substrate and third, galvanic attack of the counterface material. These three types are discussed and solutions suggested.