GCr15钢接触表面塑性形变强化与裂纹萌生机制

对轴承钢GCr15在油润滑条件下开展滚动接触疲劳试验, 利用扫描电镜和透射电镜对疲劳样品亚表面微观组织进行观察, 并分析塑性变形层微观结构变化引起的形变强化和裂纹萌生机制. 结果表明: 在摩擦力作用下, 接触表面组织发生塑性流动是由于晶界处的位错滑移使晶粒产生滑移变形, 越接近表面组织滑移变形越严重, 硬度也越高; 塑性变形层内有纳米晶产生, 并有部分碳化物溶解, 无相变发生; 由于在塑性变形层的晶界处产生孔洞而出现层状纤维组织, 孔洞在循环应力的作用下形成裂纹; 塑性变形层的厚度随着接触应力和循环次数的增加而增加.

The mechanism of plastic deformation strengthening and crack initiation on GCr15 steel contact surface

The rolling contact fatigue test of GCr15 bearing steel was carried out under oil lubrication condition. The subsurface microstructure of the failed samples after rolling contact fatigue test was investigated by using scanning electron microscopy and transmission electron microscope, the deformation strengthening and crack initiation mechanism caused by the change of microstructure of plastic deformation layer was also analyzed. The results showed that the plastic flow in the plastic deformation layer is caused by the dislocation slip at the grain boundary resulting in the slip deformation of the grain under the action of friction. The closer to the contact surface, the more serious the slip deformation is and the higher the hardness value is. There are nanocrystals formed and some carbides dissolved in the plastic deformation layer, with no phase transformation appeared. The appearance of layered fibrous structures is resulted from the formation of holes at the grain boundaries in plastic deformation layer, while the holes form cracks under the effect of cyclic stress. The thickness of plastic deformation layer increased with the increase of contact stress and cycle times