High temperature tribological properties of D-gun Al2O3 coatings in fluoride molten salts

Abstract

Anti-corrosion and wear-resistance coating is important to the reliability of the mechanical systems served in molten salt media. In this work, the Al2O3 coating was prepared on the stainless steel surface by a detonation gun (D-gun) spraying technique and its high temperature tribological properties in FLiNaK molten salt were studied systematically by sliding it against SiC, Al2O3 and steel materials. The results indicated that the Al2O3 coating has a high bonding strength of above 50 MPa with a porosity of 0.8 %. The tribological properties of the Al2O3 coating is significantly influenced by the counterface materials. The friction coefficients are between 0.14 and 0.45, and the wear rate increases from 2.2 × 10−5 mm3/N·m to 19.1 × 10−5 mm3/N·m by sliding it against SiC, Al2O3 and steel materials. The worn surface morphologies and compositions were specifically studied and correlated to these distinct behaviors.