Fatigue in Low Pressure Carbonitrided Steels
Low pressure carbonitriding and pressurized gas quenching heat treatments were conducted on four steel alloys: 20MnCr5, 20MnCr5 + B, SAE 8620 and SAE 8620 + Nb. Bending fatigue tests were performed with Brugger specimens to simulate fatigue on the tooth root of a gear. The heat treatment parameters were modified to ensure the surface hardness and effective case depths were comparable for the four alloys. The profiles for hardness, retained austenite, residual stress, carbon and nitrogen were comparable for all the alloys. However, the fatigue performance of each alloy was different. The highest ...
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