Research On The Effect Of Enhanced Grinding Target Shooting Distance On The Friction And Wear Properties Of GCr15 Bearing Steel

GCr15 bearing steel is the most important material for manufacturing bearings,and the manufacturing level of bearings directly affects the improvement of the comprehensive strength of the country.Therefore,it is very important to strengthen the surface of GCr15 bearing steel so as to make the bearings work longer.In this paper,GCr15 bearing steel surface is strengthened by grinding with different target shooting distances to study the friction and wear properties of the processed bearing steel.Intensified grinding is a gas-solid-liquid three-phase mixing flow jet processing technology.At present,the research on the effect of target distance on the friction and wear properties of GCr15 bearing steel is still in a blank state.Therefore,the research in this paper is meaningful for enriching the theoretical system of strengthening grinding.The main contents and conclusions of this paper are as follows:(1)The influence of target shooting distance on intensified grinding is discussed theoretically.The force acting on the projectile after leaving the nozzle is analyzed and sorted out.Combining the quasi-rigid body model,continuous model and hard sphere model,and oblique impact theory,the impact of projectile on GCr15 bearing steel is analyzed theoretically.The residual compressive stress and grain refinement of GCr15 bearing steel after intensive grinding were analyzed theoretically.(2)The processing of different target range(60mm,90 mm,120mm and 150mm)is simulated and analyzed by means of the discrete element software EDEM.It is found that with the increase of target distance,the plastic deformation of bearing steel along X-axis and Z-axis first increases slowly,then decreases slowly.The deformation of steel plate with target distance of 90 mm is the largest,and that of steel plate with target distance of 60 mm is the smallest.According to the proper increase of deformation of bearing steel,it is helpful to form a better surface layer.Therefore,it can be preliminarily inferred that the bearing steel with a target distance of 90 mm has the best processing effect.(3)GCr15 bearing steel was strengthened by grinding with different target distance(60mm,90 mm,120mm and 150mm).Then the thickness of the surface strengthening layer was analyzed by DMI3000 M metallographic microscope.It is found that with the increase oftarget distance,the thickness of the hardening layer first increases slowly,then decreases slowly.The thickness of the hardening layer of the sample with target distance of 90 mm is the largest,and that of the sample with target distance of 60 mm is the smallest.The microhardness of the hardened layer of bearing steel sample was measured and analyzed by equal distance(20μm).It is found that the hardness increases slowly with the increase of surface depth.When the depth reaches 100μm,the hardness decreases rapidly until it is equal to the hardness of GCr15 bearing steel matrix.Six groups of friction and wear tests were carried out on GCr15 bearing steel samples with different shooting distances from intensified grinding targets.Each group of experiments is to select a sample of 90 mm and 150 mm shooting distance without processing and intensifying grinding.Experiments show that the friction coefficient fluctuation range of GCr15 bearing steel samples with target-shooting distance of 90 mm is smaller than that of samples with target-shooting distance of 150 mm during stable wear stage,90 mm friction performance is better.Within 30 minutes,the wear of two samples with target distance of90 mm and 150 mm are similar,and the target distance has little effect on the wear resistance of GCr15 bearing steel.