1, cold plastic deformation layer: in the grinding process, every moment of abrasive is equivalent to a cutting edge。However, in many cases, the front Angle of the cutting edge is negative, and the abrasive particle in addition to the cutting effect is to make the workpiece surface withstand the extrusion action (ploughing action), leaving an obvious plastic deformation layer on the workpiece surface。The degree of deformation of this deformation layer will increase with the degree of grinding bluntness and the increase of grinding feed。
      2, thermoplastic deformation layer: The instantaneous temperature formed by grinding heat on the working surface, so that the elastic limit of the workpiece surface layer at a certain depth drops sharply, and even reaches the degree of elasticity disappearance。At this time, the working surface layer is free to stretch under the action of grinding force, especially compression force and friction force, which is limited by the base metal, and the surface is compressed (more), causing plastic deformation in the surface layer。The high temperature plastic deformation increases with the increase of workpiece surface temperature when the grinding process is unchanged。
      3, work hardening layer: sometimes with microhardness method and metallography can be found, due to processing deformation caused by the surface layer hardness increase。
In addition, in addition to grinding processing, the surface decarburization layer caused by casting and heat treatment heating, if it is not completely removed in the future processing, remaining on the surface of the workpiece will also cause surface softening and deterioration, contributing to the premature failure of the bearing。