ABSTRACT
An oxidised CoNiCrAlY overlay coating has been studied in cross-section by means of imaging SIMS. The scale consisted mainly of aluminium oxide, with chromium in the outer part The yttrium was very unevenly distributed in the scale and in the underlying metal; the possible implications of this for the adhesion of the scale are discussed. The results show the power of imaging SIMS for studying the distribution of elements which are present in very low concentrations. A preliminary experiment using oxygen-18 as a tracer showed that the scale grew primarily by means of oxygen difusion inwards.
