THE PARTITIONED STRAINRANGE FATIGUE BEHAVIOR OF COATED AND UNCOATED MAR-M-302 AT 10000C (18320F) IN ULTRAHIGH VACUUM

摘要

Elevated temperature (1000℃ (1832℉)) vacuum fatigue tests have been conducted on uncoated and aluminide (PWA 45) coated cobalt-base MAR-M-302 alloy with the four different types of thermal-mechanical reversed inelastic strain cycles (wave shapes) defined by the method of strainrange partitioning. Results of these tests indicated two major conclusions. First, there was no significant influence of the aluminide coating on the thermal-mechanical fatigue life of the MAR-M-302 alloy. Second, variations in the type of thermal-mechanical fatigue cycle applied caused significant variations of fatigue life for both coated and uncoated material. The longest lives were achieved with εpp type cycling, while the εcc cycle caused a reduction of fatigue life of about 1/2 order of magnitude with respect to the εpp life. Theεcp type cycle caused a life reduction of between 1-1/2 and 2 orders of magnitude relative to the εpp life, while the εpc type cycle provided a fatigue life which appeared to be comparable to that generated by the εcc cycle.