Surface analysis of a heat-treated, Al-containing, iron-based superalloy

The surface composition of MA 956 superalloy both as-received and after fou r exposure times at 1100 degrees C has been investigated by energy dispersi ve x-ray spectrometry (EDX) and x-ray photoelectron spectroscopy (XPS). The passive layer of the as-received sample is mainly formed by Cr- and Fe-oxi des, Heat treatment leads to the formation of an alumina layer on which sma ll nodules grow. XPS spectra evidence the presence of titanium and yttrium oxides at the surface of the heat-treated samples, suggesting Y and Ti outw ard diffusion through the alumina layer. Iron and chromium oxides at the to pmost surface layers are observed only for short heat-treatment times.