Oxidation resistance of (Ti, Al, Si)N coatings in air

Abstract (Ti, Al)N and (Ti, Al, Si)N coatings were annealed in air at temperatures ranging from 500 to 900 °C. The Ti .35 Al .65 N and Ti .62 Al .38 N form a protective superficial layer of Al 2 O 3 , protecting the underlying nitride from further oxidation. Despite its higher aluminium content, the Ti .19 Al .81 N and the Ti .27 Al .73 N develop a homogeneous oxide layer for all the oxidation temperatures, exhibiting the lowest oxidation resistance, very similar to that of AlN. The Ti .70 Si .30 N forms a homogeneous oxide layer, with an oxidation resistance similar to that of Ti .62 A .38 N. The Ti .62 Al .26 Si .12 N forms a two-phase scale as in the Ti .62 Al .38 N, but the oxidation resistance is slightly lower. The Ti .27 Al .53 Si .20 N shows, for temperatures below 800 °C, the formation of a homogeneous oxide layer, while for temperatures between 800 and 900 °C, an Al enrichment at the top layer is observed, which is responsible for a better oxidation resistance at 850 °C than that at 750 °C.