Failure Analysis on Bending of 40Cr Steel Switching Support Shaft

By means of chemical compositions analysis, metallographic examination, hardness test and tensile test, the bending failure reasons of a 40Cr steel level 2 switching support shaft were analyzed. The results show that because the hardness range illustrated in the design paper was too wide and the manufacturer could not determine the heat treatment process, the hardness and strength of the support shaft was lower than the wanted values, and bending failure happened during running-in test. By appropriately reducing the tempering temperature and raising the hardness and strength of the support shaft, the bending failure problem could be well resolved.