Microstructure and oxidation resistance of aluminide layer produced on Inconel 100 nickel alloy by CVD method

Abstract

Abstract The study was concerned with heat-protection of the IN 100 nickel superalloy by covering it with a diffusive β-NiAl intermetallic layer produced by the CVD method. Oxidation resistance tests were conducted at 950 °C in air. The alloy samples, with and without the intermetallic layer, were subjected to 24 heating-cooling cycles each lasting for 24 h and then their oxidation resistance was compared. During the oxidation tests, the stress induced in the coatings was analyzed by the finite element method which was also used for monitoring the growth of the α-Al2O3 scale during the successive thermal cycles (birth & death element analysis). The aluminum oxide scale appeared to be continuous and compact. The stress level depended on the surface roughness of the interface between the intermetallic layer and the oxide scale and was the highest in the region of its surface peaks and the lowest in the valleys where it was compressive. The coatings composed of the diffusive β-NiAl intermetallic layer, about 11 μm thick, and the α-Al2O3 scale had a high thermal shock resistance and very good corrosion resistance.