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Evaluation of Carborundum (CBO) injection-molded sintered alpha-silicon carbide (Sic) AGT 100 gasifier turbine rotors by spin testing established a baseline for material strength characteristics. Spin test results of a subsequent group of rotors demonstrated a reduction in average failure speed. Post-test fracture analysis identified surface and near-surface flaws in the back face region to be the typical failure origins. Corrective actions were initiated to address the elimination of the strength-controlling flaws. Initial evaluation of rotors fabricated to these process modifications indicates improvements in overall surface quality and average burst speed.

Effects of specimen thickness and orientation on creep and stress-rupture properties of two advanced single crystal alloys were investigated. The alloys were CMSX-3, a derivative of Mar-M247, and a new single crystal alloy, designated as Alloy X, which is based on modification of IN-792 composition. Section thickness effects were ascertained utilizing four different specimen geometries, including 0.250 in. diameter bars and 0.020 in. thick specimens. The stress-rupture lives of both materials degraded with section thickness at stress levels less than 40,000 lb/in.2. The life degradation was approximately 3X at 20,000 lb/in.2. Investigations into the effects of orientation on stress-rupture properties indicated that for Alloy X the <110> oriented specimens suffered a loss of approximately 3X in stress-rupture lives compared to <001> oriented specimens.