Improvement Of Oxide Layer Stability By Use Of Chemical Surface Attack

A new method is proposed to improve the adhesion and temperature cycling stability of oxide layers on nickel-base structural alloys. In contrast with other approaches in which reactive metals, rare earth elements or dispersions of stable oxides were added, an active surface modification technique is applied in this work. An aluminium dipping-removal procedure is used which results in a smoothing of the surface, locally enriches the aluminium and creates nuclei for the development of oxide pegs during subsequent controlled oxidation. Deuterium permeation measurements have been used as a means of quantifying the damage state of the oxide scales which is a result of temperature cycling. The results demonstrate that chemical surface treatment leads to superior stability of the oxide scales. This is attributed mainly to the occurrence of oxide pegs which could be identified after metallographic preparation and examination.