Research On The Structure Change And Corrosion Resistance Of The Bearing Ring In The Strengthened Grinding Process

Bearings are not only the basic parts of various intelligent equipment,but also the support points of power and motion,which directly affect the performance of the entire equipment and the reliability of the function.This subject takes GCr15 bearing steel as the research object,and uses the new technology of reinforced grinding to process the working surface of the bearing to change its internal structure,and study the effect of the process on the corrosion resistance of GCr15 bearing material.Firstly,based on the theory of elastic half space,the mechanism of the structure change of the bearing ring during the reinforced grinding process is theoretically analyzed,and the relationship model between the material distortion and the corrosion rate is derived.The samples under different processing times were obtained by reinforced grinding treatment,and hardness test,XRD ray diffraction,cross-section metallographic observation and SEM observation were carried out to analyze the variation of bearing rings over time.Then,the samples after the orthogonal test of the enhanced grinding were subjected to a potentiodynamic scanning electrochemical corrosion test to analyze the effects of different processing techniques on the corrosion resistance of GCr15 bearing materials.The main conclusions are as follows:(1)After the reinforced grinding process,the microhardness of the near surface of the bearing ring is increased by about 10%compared with the untreated sample,and the hardness of all processed samples decreases from the highest value of the surface layer to the core direction,and finally close to the hardness of the unprocessed sample.With the extension of processing time,the grain refinement of the sample surface is more uniform,and the dislocation density is gradually increased.(2)The reinforced grinding treatment causes the bearing raceway surface layer to introduce a plastic deformation layer having a gradient change.Under the processing condition of 0.6MPa,with the extension of processing time,the shape strengthening layer gradually increased.After 8 minutes of processing,the thickness of the strengthening layer has increased to 100?m,and since then,it has increased slightly and tended to be stable.(3)Electron microscopic observation of the bearing sample of 0.6MPa-6min reinforced grinding shows that the shape of martensite cannot be distinguished in the area of 15?m near the machined surface;the martensite at 50?m appears in multiple directions and is mutually delivered;The coarse streaks of martensite can be clearly seen at 100?m while the orientation of most stripes is uniform.(4)From the results of electrochemical corrosion,the corrosion resistance of each sample after the enhanced grinding was improved,and the sample with the lowest corrosion rate was reduced by about 27?A/cm~2 compared with the sample without the reinforced grinding.By comparing the lowest corrosion rate sample with the highest original sample,it can be seen that after the reinforced grinding process,the increase of dislocation density,grain refinement,the change of various elements on the surface and the increase of residual stress on the surface of bearing rings are helpful to improve their corrosion resistance.(5)The significance test shows that the influence of processing pressure and processing time on the corrosion resistance of the bearing is much greater than the influence of the motor speed.The better process parameters:processing time is 10 min,processing pressure is 0.7MPa,motor rotation speed is 200 rpm.