Study Of The Shot Peening Treatment And Its Characteristics On The Suface Of Heavy Duty Locomotive Traction Gear

Shot peening is considered as a widely used application for the surfacetreatments of material, which enables a great increase of anti-fitigue andanti-rust capabilities. It may be featured with the advantages of wideapplication range, easy operation, higher effectiveness and lowerenergy-cosuming. By using five different kinds of shot peening parameters,this article executes experiments on four types of heavy-load locomotivetraction gears with materials of18CrNiMo7-6、20CrMnMo、20CrNi2Mo and42CrMo. Then, with the help of X-ray diffraction instrument、micro hardnessdevice and the technology of electronic-chemical peeling, the article displaysthe effects of these five processes on the facial residual stress、full width athalf maxium (FWHM), residual austenite and micro-hardness along with thethickness from the surface of the four gears.The experiments give the conclusion that: with each of the five shotpeening treatment for each material, the residual stresses increase to themaximum value along with the thickness, then, it begins to decrease.Thehigher is the intensity of shot peening, the higher are the facial residualcompressed stress values and the maximum residual compressed stressvalues.By observing the distribution of FWHM of the different shot peeningtreatment, it is found that it may increase greatly. The higher is the intensity,the greater is the width of FWHM. For the same intensity of shot peening, theFWHM decreases along with the increase of thickness and finally reach thesame lever with the matix. After the shot peening treatment, all the contents of facial residualaustenite are lower than1%no matter which the process is. For one materialwith the same shot peening treatment, the content of residual austenite mayincrease along with the thickness and finally reach the same level of matix.At the same time, the higher is the intensity, the more is the amount ofaustenite transforming to martensite, and the deeper is the effected zone.The facial hardness may increase by20%after shot peening. For onematerial with the same shot peening treatment, the micro hardness valuedecreases graduately from the surface and reaches the same level with thematrix.The higher is the intensity, the higher is the micro hardness value.This article may be concluded as follow: with the same gear material,the distribution of residual compressed stress、X-ray FWHM、residualaustenite and micro hardness can be greately improved by increasing theintensity of shot peening. With the condition of not having the over-shotpeening phenomenon and within the range of maximum air pressure of shotpeening machine, the higher is the shot peening intensity, the better is theresults. For the carburization and induction gears, considering its differencesof gear facial hardness, the differences of material performance after shotpeening is greater. The residual compressed stress、X-ray FWHM width、residual austenite and microhardness of induction gears increase morecompared to the carburization gears. We may draw the conclusion that, thefacial hardness has a great effect on improving the performace of gears aftershot peening. The identical shot peening treatment can be applied for thegears with the same heat treatment methods and the same facial hardness.