Investigation to develop a high strength eutectic for aircraft engine use. Final report, 1 Aug 1970--31 Jul 1971. [Ni/sub 3/Al--Ni/sub 3/Nb]

Technical Report · Sat Jul 31 00:00:00 EDT 1971

OSTI ID:7223302

Thompson, E R; Kraft, E H; George, F D

Properties of the Ni/sub 3//sup 3/Al--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 strength 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. (auth)

• Research Organization: United Aircraft Corp., East Hartford, CT (USA)
• DOE Contract Number: N00019-71-C-0096
• OSTI ID: 7223302
• Report Number(s): AD-887395
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM ALLOYS
FRACTURE PROPERTIES
NICKEL BASE ALLOYS
NIOBIUM ALLOYS
EUTECTICS
FAILURES
GAS TURBINES
INTERMETALLIC COMPOUNDS
LAMELLAE
MATERIALS
MICROSTRUCTURE
PROTECTIVE COATINGS
SOLIDIFICATION
TERNARY ALLOY SYSTEMS
ALLOY SYSTEMS
ALLOYS
COATINGS
CRYSTAL STRUCTURE
MECHANICAL PROPERTIES
NICKEL ALLOYS
PHASE TRANSFORMATIONS
TURBINES
TURBOMACHINERY
360103* - Metals & Alloys- Mechanical Properties