Mitigation of FOD and Corrosion Fatigue Damage in 17-4 PH Stainless Steel Compressor Blades With Surface Treatment

摘要

Compressor blades of a military aircraft turbine engine made of 17-4 PH stainless steel have been reported to have blade edge foreign object damage (FOD), corrosion pitting, and erosion damage that reduce fatigue life. This paper reports the findings of a comprehensive investigation of the effect of residual compressive stresses, imparted by various surface treatments, to improve leading edge damage tolerance and active corrosion fatigue performance in a salt water environment. Initial fatigue and corrosion fatigue tests were conducted in feature specimens designed to simulate the geometrical conditions of thick section and blade leading edges of compressor blades. The FOD tolerance and corrosion fatigue performance of 17-4PH prepared by low plasticity burnishing (LPB), shot peening (SP), and low stress grinding (LSG) were compared. LPB dramatically improved both high cycle fatigue (HCF) and corrosion fatigue performance, providing tolerance of 0.040 in. deep FOD in thick section and 0.050 in. deep leading edge FOD. Shot peening afforded little benefit in the presence of FOD 0.010 in. deep. Fatigue initiation at relatively low applied stress levels originating from existing corrosion pits outside of the LPB treated zone limited the ability to test the surface treatments on actual fielded T56 blades retired from service. In the absence of prior pitting, LPB provided 0.020 in. deep FOD tolerance on new T56 blades. Both the damage tolerance and active corrosion fatigue performance of 17-4PH in salt water increased with the depth of the compressive zone produced.