Research Of Strengthening Technology And Properties With Bionics Non-smooth Surface By Laser Melting

Wear and fracture are the main failure modes of metal parts,and the source of these failures often comes from the surface of parts.Therefore,strengthening the surface of parts is great significance for improving the service life of parts.Dung beetles,shells,armadillos and other organisms have gradually evolved a body surface with good wear resistance because they live in sand or soil for a long time.Therefore,in this paper,45 steel was used as the test material,and the above biological surface was used as the biomimetic model to design and prepare point-like,strip-like and grid-like non-smooth biomimetic surface,and study the wear resistance and mechanical properties of non-smooth biomimetic surface samples.The influence of laser coagulation parameters on the depth of bionic cell was studied firstly.Orthogonal test and single factor test were used to optimize the parameters of laser coagulation.The results show that the effects of laser coagulation parameters on the depth of penetration are current,pulse width,frequency and scanning speed.Among them,laser current has a great influence on the fusion depth of the bionic element,and laser pulse width has a great influence on the contour of the bionic element.The optimized process parameters were: current 180 A,pulse width 8ms,frequency 6Hz,scanning speed120mm/min.After the optimized laser melting process,45 steel can be divided into melting zone,phase change zone and heat affected zone.The melting zone consists of fine needle-like and plate-like martensite with a hardness of 750HV0.2.The phase transition region is composed of a large number of martensite,and its grain size is 3-5 times that of the melting zone.The average microhardness is about 520HV0.2.The wear test results show that the wear resistance of the bionic samples treated by laser non-smooth surface is better than that of the untreated samples.In the wear system with point-surface contact,the wear resistance of the point-surface non-smooth surface is the best,followed by the grid-like surface,and the strip-like surface is lower than the point-surface and grid-like surface.In the surface contact wear system,the wear resistance of the meshed non-smooth surface is the best,followed by the meshed surface,the strip surface is lower than the point surface and the meshed surface.The bionic treatment of laser non-smooth surface forms a regularly distributed "soft"(matrix)and "hard"(element)interphase structure on the surface of the sample.The bionic element with high hardness can play a supporting role in the wear process of the wear pair and bear the wear,thusslowing down the wear of the matrix.The surface of 45 steel after different shape bionic treatment the tensile strength increased,the tensile strength and the bionic unit form and its interaction Angle has a certain relationship,90°grid bionic morphology specimen tensile strength increased most obviously,7.3% increase over the matrix sample;The strip bionics sample was next,which was 5.8% higher than the matrix sample.30°grid bionic morphology specimen tensile strength increased by 3.9%.Thestrengthening effect comes from the microstructure refinement of bionic cells and the formation of soft and hard interphase structures on the surface of materials.The strengthening effect mainly comes from the microstructure refinement of bionic cells and the formation of soft and hard interphase structures on the surface of materials.