An XPS Study with Depth Profiling for the Surface Oxide Layer Formed on Aluminides Produced on Superalloy 690 Substrates

摘要

Superalloy 690 substrates containing mainly Cr and Ni aluminides on the uppermost surface, formed by atmospheric plasma spraying and heat treatment, were oxidized at 1273 K in air for 2 h. Quantitative X-ray photoelectron spectroscopy (XPS) analyses indicated that the outermost surface layer formed on aluminides is composed of similar to 21.0 at.% Al+3 (as Al2O3), 17.0 at.% Al-0 (elemental aluminium), 1.4 at.% Cr+3 (as Cr2O3) and 60.5 at.% O (in Al2O3 and Cr2O3 and also includes oxygen contaminant). Surface sputtering for 5 min exhibited splitting of Cr2p(3/2) peak into a doublet comprising Cr+3 (0.9 at.%) and Cr-0 (0.4 at.%) with the presence of 1.15 at.% Ni-0 in the surface layer that mainly contained similar to 37.3 at.% Al+3, 7.3 at.% Al-0 and 52.9 at.% O. Surface sputtering for 15 min indicated surface composition similar to surface sputtered for 5 min but with a marked reduction in ratio of Al+3/Al-0 (32.2 at.% Al+3/11.90 at.% Al-0) in the surface layer.