Development of sintered alpha silicon carbide (SASC) gas turbine rotors commenced in 1979 and is being continued through 1986 under the AGT-100 (Advanced Gas Turbine) program where the Allison Gas Turbine Division (AGTD) of General Motors is the prime contractor. Injection molding of a solid one piece rotor was the chosen fabrication technique.
Compound development in connection with the appropriate binder removal process suitable for a wide variety of wall thicknesses were critical steps early in the program. Various molding conditions and injection procedures were evaluated to obtain acceptable rotors. Non-destructive evaluation (NDE) methods as well as destructive measures were used to evaluate molded, baked, and sintered rotors. These results and related processing studies will be discussed in detail.
Current rotors fabricated with the improved procedures show increased molding yield and a lower variability in strength. Rotors have been proof tested to 95,000 rpm (110% of design speed) which is equivalent to about 600 m/s tip speed.