PROTECTIVE COATINGS OBTAINED BY LASER TRE ATMENT OF THE LOW-ALLOYED FERRITIC STEEL-35 NCD-16

The oxidation resistance and the hardness of a ferritic steel (Fe-0.38 % C-1.8 % Cr-4 % Ni) are largely improved by superficial incorporatio n of predeposited Cr3C2 only or of Cr3C2 followed by SiC. The incorpor ation is achieved by simultaneously melting of the predeposited carbid es and the superficial parts of the substrate. In the first case the p rotection against oxidation results from the growth of a spinel subsca le FeCr2O4 in contact with the coating. In the second case the presenc e of silicon allows the growth of a Cr2O3 scale which, joint with that of silica, leads to a spectacular protection.