Gear is the main part of power transmission in all kinds of machinery. During operation, the tooth surface of the gear is affected by periodic bending stress and contact compressive stress; When starting, shifting and vibrating, the tooth root will be subjected to sudden impact force; The tooth surfaces roll and slide with each other, and there is a large friction.
Under the action of various stresses, the damage forms of gears are mainly tooth fracture, tooth surface peeling and fatigue wear. Therefore, the gear is required to have the following main properties:
(1) high bending fatigue strength and high contact fatigue strength;
(2) the tooth surface has high hardness and high wear resistance;
(3) the core shall have sufficient strength and toughness.
However, due to the heat treatment process of the gear and the materials of the parts, various heat treatment defects are caused, which accelerate the local damage or even complete failure of the gear.
Based on the analysis of the stress state of the gear, the necessary mechanical performance requirements are put forward. At the same time, the defects easy to appear in the process of gear heat treatment and their influence on the service performance are discussed and analyzed.