Study On Preparation And Performance Of Surface Modified Layer Of Low Carbon Steel By Supersonic Particle Bombardment

Low-carbon steel and low-carbon alloy steel are the most widely used in the engineering field.However,when strengthening precision instrument parts,supersonic particle bombardment is often used.Using Supersonic Fine Particles Bombarding(SFPB),a nano-fine layer with a certain thickness can be prepared on the surface of the material.If activated carbon is incorporated in the process of supersonic particle bombardment treatment,a carbon-containing hardened layer can be formed on the surface of the material at room temperature.Therefore,by supersonic particle bombardment to induce surface nanocrystallization combined with subsequent heat treatment,a uniform and dense carbon-rich nanocrystalline layer can be formed,and the performance of the material surface modification layer can be improved.In this paper,high-quality low-carbon alloy steel 20Cr2Ni4A is used as the base material,supersonic particle bombardment technology is used to strengthen the surface of 20Cr2Ni4A steel,and the structure and properties of the modified layer are studied.Combine annealing and rare earth infiltration process to explore element diffusion mechanism.Draws the following conclusions:1.After SFPB treatment for 6 minutes,a carbon-containing nano-modified layer is formed on the surface of 20Cr2Ni4A steel under the two processes of simultaneous powder feeding and pre-activated carbon.The thickness of the carbon-containing modified layer is 3-5?m.The size of the nanocrystalline grains becomes smaller,reaching 24.5nm and 21.0nm,respectively.The surface hardness of the material can be increased by introducing carbon element combined with supersonic particle bombardment treatment(the hardness of the matrix is increased by about89.3%)to 428.1 HV_0.2.2.Subsequent annealing treatment will affect the structure and performance of the modified layer.Annealing treatments at 300°C,400°C and 500°C respectively,and the best results after the sample is annealed at 400°C for 120 minutes.The crystal grain size is guaranteed to be on the order of nanometers,and the crystal grain size is 20-50nm;the thickness of the carbon-containing modified layer is obviously increased,and the maximum thickness is about 8?m.3.The types of rare earth elements and the addition of rare earth elements have a certain impact on the structure and performance of the modified layer.After the annealing treatment,La₂O₃ and Ce O₂ are both present in the modified layer after the SFPB treatment of the mixed powder of rare earth elements and activated carbon.The matrix phase and the carbide phase are the main phase components on the surface of the modified layer.The thickness of the carbon-containing modified layer is about 16.8?m and 15.2?m,respectively,and the diffusion depth of carbon is increased by 69-72.6%.The wear resistance of the modified layer with La₂O₃ was improved,and the weight loss of abrasion was reduced by 41.7%.4.Adding La₂O₃ and Ce O₂ elements to 20Cr2Ni4A during supersonic particle bombardment can improve the corrosion resistance of the material.The corrosion resistance of the surface modification layer of La₂O₃ is better than that of the sample with the rare earth element Ce O₂,indicating that the La₂O₃ grains are more obvious.The material organization is more uniform.