Stress-strain state of a gear from high-strength cast iron with diffusion carbide coating

The article investigates the stress-strain state of a gear pair made of high-strength cast iron VCh 60 with a diffusion coating. We investigated three types of diffusion coating: with vanadium, chromium or manganese. Diffusion coatings were formed by chemical-thermal treatment of the studied elements in a container with a fusible seal from a powder filling. The coating thickness in all cases was 50-60 µm.The coated gears were then hardened in a protective layer. The reheat temperature was 920-930 ℃. Vanadium oxide alloy with a melting point of 675℃ was used as a protective medium (flux).This made it possible to form high hardness in the coatings and the transition zone from the coating. An external mechanical coating was applied over the diffusion coating using metal brushes. The study of the stress-strain state of the gear wheel was carried out by mathematical modeling using the Ansys package.The solution of the contact problem made it possible to obtain the law of distribution of normal and shear stresses over the section of the teeth.As a result, it was found that the maximum contact stresses in the cavity of the teeth are concentrated in the layer of thermal diffusion coating, the strength characteristics of which are several times higher than the characteristics of the base material of the wheel tooth.The level of shear stresses under the diffusion layer turned out to be two times lower than in the layer itself.As a result, the risk of pitting at the base of the teeth and surface cracks, which quickly lead to loss of gearing performance, has been reduced.