基于微晶刚玉砂轮的20 CrMnTi齿轮成型磨削表面完整性

为研究微晶刚玉砂轮成型磨削20CrMnTi齿轮的表面完整性,开展了20CrMnTi齿轮成型磨削试验,分析了砂轮线速度、轴向进给速度及径向进给量对齿面粗糙度、表层/次表层显微硬度、微观组织和残余应力的影响规律,探讨了由磨削引起的磨削烧伤、微观裂纹等损伤缺陷的形成机理,结果表明:径向进给量对表面粗糙度的影响最显著,砂轮线速度次之,轴向进给速度最不显著;磨削温度过高会导致磨削烧伤,淬火烧伤使得表面硬度提高5%~20%,回火烧伤则导致表面硬度不同程度地下降;表层组织从外至内分别为白层、暗层和基体组织,白层主要由致密的马氏体+碳化物+残余奥氏体组成;砂轮线速度和径向进给量的增大使得由磨削引起的残余拉应力增大,表面残余压应力下降并逐渐向拉应力转变,当表面最终残余拉应力大于材料的断裂强度时,表面产生微观裂纹.

Surface integrity of form grinding 20 CrMnTi gear based on a new microcrystalline corundum wheel

To study the surface integrity of 20CrMnTi gears for form grinding by a microcrystalline corundum wheel, a grinding experiment on 20CrMnTi gear was performed. Furthermore, the effects of wheel speed, axial feed rate, and radial feed on tooth surface roughness, hardness, microstructure, and residual stresses of the surface/subsurface were studied. The mechanism of the damage caused by grinding and micro-cracks was discussed. The results show that the effect of radial feed on the surface roughness is the most significant. The wheel speed is then the second most significant, and the axial feed rate is the least significant. In addition, an excessive grinding temperature leads to grinding burns, which the quenching burns cause the surface hardness to increase by 5%-20%, and the tempering burns cause the surface hardness to drop by varying degrees. The surface/subsurface structure is composed of a white layer, dark layer, and bulk material, with the white layer on the top and the bulk material being on the bottom. The white layer is composed of a dense martensitic structure, carbide, and retained austenite. The increase in the wheel speed and radial feed then increases the residual tensile stress caused by grinding. Surface residual compressive stress decreases and gradually changes to tensile stress. When the final residual tensile stress is greater than the breaking strength of the material, the surface produces micro cracks, compromising the integrity of the surface.