Improvement of Fatigue Strength of Maraging Steel by Shot Peening

摘要

Rotating bending fatigue tests up to 10~8 cycles were carried out to investigate the effects of shot peening on the fatigue strength and the fracture mechanism in wide range of fatigue life of an 18 percent Ni maraging steel by using shot particles of various sizes or hardness. Fatigue strength was increased markedly by shot peening in the wide region of fatigue life. The S-N curves showed duplex S-N properties because of the transition of fracture origin from the specimen surface in the short life region to the subsurface in the long life one. Double shot peening by using superhard fine particles was effective to improve the fatigue strength for surface fracture, though the fatigue strength for an internal fracture was only slightly influenced. Fatigue strength for the internal fracture was increased by formation of reversion austenite, suppressing intergranular cracking.