Fundamental Research Directed to Advanced High Temperature Coating Systems Beyond the Current State-of-the-Art Systems.
Abstract
The oxidation in air of nickel-silicon alloys with compositions extending from 5 to 20 weight-silicon have been studied over the temperature interval between 900 and 1100 degs C. In the case of alloys with less than 20% silicon, the silicon is not oxidized internally nevertheless the rates of oxidation are greater than those for alloys upon which alumina scales are formed. The alloy with 20% silicon exhibited oxidation rates less than those associated with alumina scales under similar conditions. The scales which developed upon the Ni-20 silicon alloy are in the process of being identified. It appears that silicon rich coatings have the potential of being used in place of present state-of-the-art MCrAlY coatings. The adherence of alumina formed on alloys of Ni-20Cr-10Al and Co-20Cr-10Al with yttrium or hafnium has been studied by using cyclic oxidation tests, acoustic emission measurements and by measuring the load required to pull scales from substrates. These studies have shown that the following parameters affect alumina scale adherence: oxygen active element type and concentration; base alloy composition (e.g. nickel-versus cobalt-base); alloy surface condition; specimen cooling rate, and exposure time of specimen to oxidation conditions. The acoustic emission technique of studying damage in alumina scales on alloys appears to provide a means of nondestructively determining the useful lives of coatings on alloys that remain after use under service conditions. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 07, 1983
- Accession Number
- ADA131618
Entities
People
- F. S. Pettit
- Gerald H. Meier
Organizations
- University of Pittsburgh