Causes Analysis on Grinding Cracks of 20CrNi2Mo Steel Gear

The causes of grinding cracks of 20CrNi2Mo steel gear were analyzed by means of macroscopic examination, chemical compositions analysis, metallographic examination and hardness test. The results show that the main reasons for the grinding cracks were the existence of serious internal oxidation and Widmanstatten cementite in the carburized region, which reduced the surface residual compressive stress of the gear grinding region and greatly increased the grinding cracking sensitivity of the gear. When the grinding stress was higher than the tensile strength of the gear material, grinding cracks would produce.