APPLICATION OF POWDER METALLURGY TECHNIQUE TO PRODUCE IMPROVED BEARING ELEMENTS FOR CRYOGENIC AEROSPACE ENGINE TURBOPUMPS

摘要

Traditionally, vacuum melted 440C stainless steel is used for high performance bearings for aerospace cryogenic systems where corrosion due to condensation is a major concern. For the space shuttle main engine (SSME), however, 440C performance in the high-pressure turbopumps has been marginal* A basic assumption of this study was that powder metallurgy, rather than cast/wrought, processing would provide the finest, most homogeneous, bearing alloy structure, regardless of the alloy(s) being considered. Preliminary testing of P/M alloys (hardness, corrosion resistance, wear resistance, fatigue resistance, and fracture toughness) was used to "de-select" alloys which did perform as well as baseline 440C. Five out of eleven candidate materials (14-4/6V, X-405, MRC-2OO1, T-440V, and D-5) based on preliminary screening were selected for the actual rolling-sliding five-ball testing. The results of this test were compared with high-performance vacuum-melted M-50 bearing steel (this 4% chromium steel lacks corrosion resistance and is used for aerospace applications where corrosion is not a major concern). The results of the testing indicated outstanding performance of two P/M alloys, X-405 and MRC-2001, which eventually will be further evaluated by full scale bearing testing.