Effect Of Laser Fabrication Bionic Remelting Element On Tensile Properties And Friction And Wear Properties Of 70Mn Steel

70Mn steel is a kind of spring steel.Its performance is similar to 70 steel,and its elasticity and strength are better than those of 70 steel.After heat treatment,it has good mechanical properties and is often used to make spring rings,valve springs,clutch reeds,brake springs,etc.Because these parts will be subjected to cyclic stress,impact and other loads in the process of work,it is easy to wear and cause damage.Therefore,it is of great practical significance to improve the strength and wear resistance of 70 Mn to extend the service life of the parts.In recent years,laser surface remelting modification technology has been more and more applied in industrial production to enhance the wear resistance of surface.Through many bionics studies,it is found that the "soft-hard" interphase element is one of the final structures of biological evolution.Therefore,this paper explores the influence of three laser bionic remelting elements on the tensile strength and friction and wear properties of original hardness(annealed)and temper treated 70 Mn steel.Firstly,the distribution of temperature field and stress field in the process of laser remelting with a laser power of 400 W and a scanning speed of 10mm/s is simulated by ANSYS software.Then,the size of remelting zone and the distribution of thermal stress are predicted according to the temperature field,so as to improve the laser remelting process.After remelting,it is found that the remelting zone changes from spherical pearlite to aciculate martensite,and the surface metal of remelting zone changes into stripe martensite,and the subsurface layer changes into aciculate martensite by observing the metallographic characteristics of the original and tempered samples.The microhardness tester was used to measure the hardness distribution of remelting zone.The test results show that the hardness of the original hardness samples increases from 150 HV to 760 HV,which increases by about 400%.After tempering,the surface hardness and matrix hardness of the remelting zone of the sample are about 325 HV,and the lower part of the remelting zone also reaches about 745 HV,which is increased by about 129%.Tensile and friction wear tests were carried out on the samples after laser biomimetic remelting.Tensile tests show that the tensile strength and elongation of the samples are reduced by the laser biomimetic remelting,the yield strength of the samples with original hardness is enhanced,and the yield strength of the tempered samples is reduced.By studying the fracture mode and fracture morphology of the sample,and combining with the metallographic structure and XRD test results,the reasons for the fracture and strength change of the sample were analyzed.In general,the biomimetic remelting elements slightly reduce the tensile properties of the samples.Friction and wear tests of samples show that:Bionic unit can effectively reduce furrow generation and reduce the depth of the furrow,enhance the wear resistance of sample,and the wear resistance of materials with the bionic unit body is enhanced by the complexity,the reason is that the bionic remelting unit cell in the process of friction materials and supporting effect,the second pit of remelting unit cell played a collection of wear debris and prevent chip movement continuity.The contact between the wear debris and the substrate is avoided to protect the substrate.In conclusion,the laser biomimetic remelting technology can improve the friction and wear properties of 70 Mn with little weakening of its mechanical properties,which provides a reference for the subsequent application of laser remelting in carbon steel.It lays a foundation for the application of laser biomimetic remelting technology in actual industrial production.