Optimising oxidation resistance of MCrAl coating systems using vapour phase alloy design

Abstract

The potential for developing new overlay coatings by codeposition from segmented or multiple sources has been investigated. The main focus of this work was the development of new NiCrAl based alloys with improved resistance to high temperature oxidation. Initially, studies concentrated on the deposition of a wide range of ternary alloy compositions by magnetron sputtering from a segmented target consisting of pure Ni, Cr, and Al segments. Hence, alloy compositions were produced by mixing of these source materials in the vapour phase. These coating compositions were deposited onto high purity Al2O3 to ensure that no interaction between the coating compositions and substrate occurred during subsequent oxidation trials. Oxidation trials at 950°C for periods up to 100 h have been undertaken. Modelling of the oxidation behaviour along quasibinary sections has allowed the construction of a ternary iso-oxidation contour map for the NiCrAl system. This approach has identified new oxidation resistant materials with a twofold improvement in oxidation resistance over typical commercial overlay coatings.MST/1093