Research Directed Advanced High Temperature Coating System Beyond Current State-of-the Art Systems

摘要

Alloy systems have been investigated to determine the reaction product barriers that can be used to provide optimum resistance to high temperature oxidation. The reaction product barriers which can be used are Al(2)O(3), Cr(2)O(3), and SiO(2) with the use Cr(2)O(3), being restricted to below about 1000 C due to formation of volatile products. The oxidation of nickel-silicon alloys has been studied over the internal 900-1100 C. Compositions of 20-22.5 Si have been found to form protective, adherent scales of SiO(2). The oxidation resistance of these alloys appears to be comparable to the most oxidation resistant alumina-forming alloys. The cracking and spalling of Al(2)O(3) scales from alloys has been described by using acoustic emission analyses to conventional analytical techniques. It has been found that acoustic emission counts can be used to indicate the damage in alumina scales. A mechanism to describe the oxidation of oxygen active elements in alloys has been developed. The effects of yttrium and hafrium on the adherence of Al(2)O(3) to NicrAl and CoCrAl alloys has been compared. It is shown that the concentration of the oxygen active elements and the substrate composition are significant factors affecting oxiude scale adherence.