GEAR HAVING EXCELLENT DEDENDUM FATIGUE LIFE AND CONTACT FATIGUE LIFE

摘要

PROBLEM TO BE SOLVED: To provide a gear which is to be subjected to high loaded specific pressure in response to the recent demand for the miniaturization, weight reduction, and applied force increase of automotive parts and has improved pitting fatigue life. SOLUTION: In the gear having excellent dedendum fatigue life and contact fatigue life: compressive residual stress at the surface is >=400 MPa; a slack quenched layer is 5-15μm thick; surface roughness Rmax is <=4.5μm; the value of Sk which means skewness as the asymmetry parameter of surface roughness distribution satisfies -1.2<=Sk<-0.5; and the area ratio of retained austenite at the surface is <=10%.