Improved silicon carbide for advanced heat engines. Final Technical Report

Technical Report · Mon May 01 04:00:00 EDT 1989

OSTI ID:5566397

Whalen, T J

The development of high strength, high reliability silicon carbide parts with complex shapes suitable for use in advanced heat engines is studied. Injection molding was the forming method selected for the program because it is capable of forming complex parts adaptable for mass production on an economically sound basis. The goals were to reach a Weibull characteristic strength of 550 MPa (80 ksi) and a Weibull modulus of 16 for bars tested in four-point loading. Statistically designed experiments were performed throughout the program and a fluid mixing process employing an attritor mixer was developed. Compositional improvements in the amounts and sources of boron and carbon used and a pressureless sintering cycle were developed which provided samples of about 99 percent of theoretical density. Strengths were found to improve significantly by annealing in air. Strengths in excess of 550 MPa (80 ksi) with Weibull modulus of about 9 were obtained. Further improvements in Weibull modulus to about 16 were realized by proof testing. This is an increase of 86 percent in strength and 100 percent in Weibull modulus over the baseline data generated at the beginning of the program. Molding yields were improved and flaw distributions were observed to follow a Poisson process. Magic angle spinning nuclear magnetic resonance spectra were found to be useful in characterizing the SiC powder and the sintered samples. Turbocharger rotors were molded and examined as an indication of the moldability of the mixes which were developed in this program.

• Research Organization: Ford Motor Co., Dearborn, MI (United States)
• OSTI ID: 5566397
• Report Number(s): N-91-24451; NASA-CR--182289; NAS--1.26:182289; CNN: NAS3-24384
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360203* -- Ceramics
Cermets
& Refractories-- Mechanical Properties
42 ENGINEERING
421000 -- Engineering-- Combustion Systems
BORON
CARBIDES
CARBON COMPOUNDS
CERAMICS
CHEMICAL COMPOSITION
ELEMENTS
FABRICATION
MAGNETIC RESONANCE
MECHANICAL PROPERTIES
NUCLEAR MAGNETIC RESONANCE
RESONANCE
SEMIMETALS
SILICON CARBIDES
SILICON COMPOUNDS
SINTERING
YIELD STRENGTH