Abstract: Aiming at the cracks on the tooth surface of 20Cr2Ni4 steel spiral bevel gear after carburizing, quenching and grinding,the uncracked tooth surface(concave) and cracked tooth surface(convex) of the cutting tooth block were measured by using optical microscope and microhardness tester. The results show that the effective hardened layer depth and microstructure at the pitch circle of the uncracked tooth surface and cracked tooth surface away from the crack of the tooth block are normal, and there is no grinding burn characteristics. There are different degrees of grinding burn characteristics at the tooth root, especially in the cracks of the cracked tooth surface, the crescent-shaped white and black grinding burn morphology, the deepest part of the burn is about 0.9 mm, and the improved grinding process parameters are put forward to avoid grinding burn.

Key words: 20Cr2Ni4 steel, spiral bevel gear, carburizing and quenching, cracked tooth surface, grinding burn