Development of Silicon Nitride Radial Turbine Rotors

To examine the possible use of ceramics as key components for automotive gas turbines, studies were conducted on radial turbine rotors made of SN-88, a newly developed, heat resistant silicon nitride. The flexural strength of MOR bars cut from various portions of the rotor was measured, and three rotors were subjected to cold spin burst testing. Time dependent strength of the rotor at high temperatures was estimated by static fatigue rupture data of tensile test pieces at temperatures up to 1400°C for up to 1000hrs. The allowable stress at an arbitrary temperature and time to failure were explained well in terms of the Larson-Miller parameter. High temperature durability was also evaluated by hot-gas spin tests. The results of these tests suggest the possibility of fabricating reliable ceramic components which might enable the realization of ceramic gas turbine engines.