Causes Analysis of Broken Teeth of 50Mn Steel Gear Ring

The 50Mn steel gear ring suffered broken teeth after a short service time. In order to find out the fracture causes, the gear ring was analyzed from the aspects of chemical composition, macro examination, hardness testing, fracture analysis and metallographic examination. The results show that the indexes of the 50Mn steel gear ring, such as chemical compositions, external surface hardness and so on, were up to the requirements of the technical agreement. There were many cracks in the hardened layer of the Gear. The depth and surface hardness of the hardened layer were not homogeneous, and not in accordance with the standard. The cause of broken teeth of the gear ring was the fatigue cracking caused by cracks in the hardened layer, which was related to improper heat treatment of the gear ring.