Experimental Study Of Two Pure Water Jets On The Surface Enhancement Of 18CrNiMo7-6

As a new technology that does not change the basic structure and quality of parts but can greatly improve the service life of parts,the anti-fatigue manufacturing technology has become the key technology of modern industry into a new era.Water jet technology has been developing rapidly in recent decades,and is widely applied in various fields including mechanical industry.With the further research of water jet technology in material modification,the advantages and application prospects of this technology are revealed.The application of water jet technology in the anti-fatigue manufacturing technology has become a new research direction,but the surface damage caused by the water jet on the surface tends to affect the strengthening effect.In order to better develop the advantages of water jet technology in the anti-fatigue manufacturing technology,this paper selects the most commonly used material 18CrNiMo7-6 gear steel in the industrial reducer as the research object.Based on the direct strengthening technology of water jet,an indirect strengthening technology for laying small steel balls on the surface of test piece is designed.Through the small steel ball on the surface of the specimen,the energy of the water jet acts indirectly on the surface of the specimen,so as to enhance the specimen.In view of the change of the surface roughness,the surface residual stress and the hardness,the strengthening effect of this method on the material is studied and compared with the traditional direct strengthening method.The main contents include:(1)The effects of direct and indirect reinforcement on the parameters of the surface layer are studied respectively when the injection pressure changes.It is found that the effect of the injection pressure on the surface residual stress of the two processes has little difference,but the influence of the indirect strengthening on the surface roughness,the surface residual stress field and the hardness is more obvious than that of the direct reinforcement.(2)The effects of direct and indirect intensities on the parameters of the test surface are studied respectively when the jet target distance changes.The experimental results show that the effect of the injection distance and the injection pressure on the two strengthening processes is basically the same.(3)Aiming at the indirect reinforcement technology,the influence of laying small steel ball diameter,layer numbers of small steel balls and times of shots on the surface parameters of the specimen is studied respectively.The results show that when the diameter is less than 3.5mm,the small steel ball can give full play to the advantage of the mass increase and improve the strengthening effect.When the diameter is larger than 3.5mm,the small steel ball is too large and affects the strengthening effect.When the small steel balls is laid within 3 layers,the protection of the small steel balls to the surface of the specimen is the main factor affecting the surface parameters.When the layer numbers is more than 3 layers,the increase of the loss of the jet energy in the transfer process becomes the main factor affecting the surface parameters,which makes the strengthening effect descend.The increase of the numbers of jet has an obvious effect on the residual stress field of the specimen.However,when the injection times exceed 3 times,the protective effect of small steel balls is weakened,which causes the influence of technology on the surface strengthening is obviously affected.