In order to reveal the relationship between the surface deformation and the microstructure as well as the properties of GCr15 bearing steel balls,the microstructure and the composition of the balls were observed and analyzed by means of optical microscopy ( OM) ,TEM and EDS. Then,the residual stress distribution in the subsurface and the content of the residual austenite were tested via a XRD process,and the hardness of the balls was tested
by using a micro Vickers hardness tester. The results show that ( 1) the matrix microstructure is composed of tempered cryptocrystalline martensites,granular M3C-type carbides and a small amount of retained austenite; ( 2) the retained austenite,whose volume fraction is 9. 75%,exists in the matrix in the film-like and the blocky forms; ( 3) a residual stress layer appears after a surface deformation-hardening treatment,which is about 0. 3 mm away from the surface; and ( 4) both the maximum residual stress and hardness appear in the subsurface being about 0. 1mm away from the surface of GCr15 steel balls.