Fatigue Crack Growth Behavior Evaluation of Grainex Mar-M 247 for NASA’s High Temperature High Speed Turbine Seal Test Rig

Abstract

The fatigue crack growth behavior of Grainex Mar-M 247 is evaluated for NASA’s turbine seal test facility. The facility is used to test air-to-air seals primarily for use in advanced jet engine applications. Because of extreme seal test conditions of temperature, pressure, and surface speeds, surface cracks may develop over time in the disk bolt holes. An inspection interval is developed to preclude catastrophic disk failure by using experimental fatigue crack growth data. By combining current fatigue crack growth results with previous fatigue strain-life experimental work, an inspection interval is determined for the test disk. The fatigue crack growth life of NASA disk bolt holes is found to be 367cycles at a crack depth of 0.501mm using a factor of 2 on life at maximum operating conditions. Combining this result with previous fatigue strain-life experimental work gives a total fatigue life of 1032cycles at a crack depth of 0.501mm. Eddy-current inspections are suggested starting at 665cycles since eddy current detection thresholds are currently at 0.381mm. Inspection intervals are recommended every 50cycles when operated at maximum operating conditions.