Polycomponent Functionally Graded Materials for Thermal Barrier Systems
Abstract
Functionally graded materials (FGMs) offer benefits for thermal barrier coating (TBC) systems for aircraft and power generation gas turbines. A preferred FGM, including the insulating ceramic outer surface and a graded inner structure on a superalloy substrate, will act both to minimize stresses due to the temperature difference between the outer surface of the FGM and the underlying substrate, and also to protect the substrate from environmental attack. Most bond coats in use are not functionally graded; they are monolithic, or, are made of discrete layers of different combinations of materials. Currently, deficiencies in bond coat performance directly impact and reduce the performance and life of TBC systems. This research is directed toward improving the durability and performance of thermal barrier systems via improved understanding of the interrelationships between the thermophysical, chemical and mechanical properties. Durability also may be improved by decreasing ceramic thickness. If nanocrystalline ceramics are shown to offer improved insulating performance, this will allow decreased ceramic thickness for performance equivalent to current ceramic layers. The overall objective of the research was to develop fundamental understandings of the physical and mechanical properties of polycomponent (three or more constituent) FGM systems as a function of phase constituents, phase volume, and microstructure. The use of three or more components in an FGM system permits the decoupling of previously dependent physical properties. For example, in a binary metal oxide-metal graded system, thermal conductivity and thermal expansion are not independent of one another, because both are functions of the volume fraction metal oxide.
Document Details
- Document Type
- Technical Report
- Publication Date
- Aug 01, 1998
- Accession Number
- ADA354114
Entities
People
- A. M. Ritter
- J. Dobbs
- Jonathan C. Zhao
- M. F. Gigliotti
- Melvin R. Jackson
Organizations
- General Electric