THE EFFECT OF THERMAL ANNEALING ON THE ADHERENCE OF AL2O3 FILMS DEPOSITED BY LP-MOCVD ON SEVERAL HIGH-ALLOY STEELS

Thin alumina films, deposited at 280 degrees C on several high alloy s teels by low-pressure metal-organic chemical vapor deposition (LP-MOCV D), were annealed at 0.17 kPa in a nitrogen atmosphere for 2, 4, and 1 7 h at 600 and 800 degrees C. Film adhesion was studied by scanning sc ratch testing (SST) and Auger electron spectroscopy (AES). The best ad hesion properties were obtained with commercial oxide dispersion-stren gthened (ODS) high-temperature alloys, especially PM 3030. Among the ' normally' high alloy stainless steels, type AISI-321 showed the best a dhesion. The other stainless steel-alumina combinations exhibited a re duced critical load, L-c, after thermal treatment. Alumina on ODS allo ys exhibited an increased adhesion. AES studies revealed that this inc rease could be explained by: (1) the presence of sulfur-trapping eleme nts, preventing segregation of sulfur at the interface; and (2) titani um and carbon enrichment at the interface, resulting in an anchoring e ffect between the oxide and the substrate.