Investigation to Develop a High Strength Eutectic for Aircraft Engine Use.
Abstract
Properties of the Ni3Al-Ni3Cb eutectic composite which may be important to its application in a gas turbine environment have been evaluated. Plane-front, directional solidification of this alloy system may be accomplished in high purity alumina investment molds provided the temperature and duration of liquid metal contact are minimized. Rapid solidification rates provide increased stregth but may, depending on the growth rate and liquid temperature gradient, produce a cellular growth front. For example, a strength as high as 88,000 psi has been measured at 2200F for the eutectic grown at 10.5 cph in the fully lamellar form. The closely spaced lamellae provide an important athermal component of hardening in this system. Below 1600F, the strength of the eutectic with a colony microstructure, produced at a fast rate, is greater than the lamellar alloy grown at a slower rate. At higher temperatures the reverse is true. This is due to the effort of the misaligned lamellae in the colony boundaries. These boundaries are weak at these temperatures and their rupture plays an important role in the failure. A hypoeutectic alloy composite containing a higher volume percent of gamma, has been successfully prepared and shown to possess increased longitudinal ductility while retaining the outstanding strengths of the eutectic. This alloy is also shown to be more oxidation resistant than the pseudo-binary eutectic. A coating system which offers protection from the high temperature corrosion of a gas turbine environment has been developed for the eutectic. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Jul 31, 1971
- Accession Number
- AD0887395
Entities
People
- Earl R. Thompson
- Edwin H. Kraft
- Frederick D. George
Organizations
- United Technologies Corporation