Improving the fretting and corrosion fatigue performance of 300M ultra-high strength steel using the ultrasonic surface rolling process

300M ultra-high strength steels (300M steels) are frequently used in the manufacture of aircraft landing gear due to their high strength and ductility. However, their high sensitivity to surface defects accelerates fatigue failure and hinders their wider application. In this work, ultrasonic surface rolling processing (USRP) was used to process 300M steel. The surface roughness, hardness, microstructure, and residual stresses before and after USRP treatment were compared. The surface roughness for USRP-treated samples (0.062 mu m) was found to be lower than that for untreated samples (0.32 mu m). In addition, a plastically deformed layer was generated on the surface of USRP-treated samples that resulted in higher hardness. Beneficial compressive residual stresses were introduced as a result of USRP treatment. The better surface finish, higher surface hardness and compressive residual stresses lead to significant improvement in the resistance of the 300M steels to fretting fatigue and corrosion fatigue. The fretting fatigue life increased from 11.9 K cycles to 56.3 K cycles, while the corrosion fatigue life increased from 29.9 K cycles to 702.1 K cycles.