EFFECTS OF CHROMIA COATINGS ON THE HIGH-TEMPERATURE BEHAVIOR OF F17TISTAINLESS-STEEL IN AIR - EFFECT OF RARE-EARTH-ELEMENT OXIDES

The MOCVD technique was used to form thin films of chromia and/or of a rare-earth-element oxide on the surface of F17Ti stainless-steel samp les. These oxides were deposited alone oi together, successively or by codeposition. Coated samples were then subjected to high-temperature oxidation tests, either under isothermal conditions at 1273 K for 50 h , or under cyclic conditions at 1223 K for 40 cycles. An improved oxid ation behavior was observed in every case, especially with codeposited Ln(2)O(3)-Cr2O3 Weight gain decreased during oxidation, compared with an uncoated sample, and scale spallation, generally observed under cy clic conditions, disappeared. Longer time experiments were also carrie d out. Large differences were observed depending on the sample-surface treatment.