Research On Microstructure And Properties Of AlCoCrFeNiSi_x High Entropy Alloy And Its Texture Coating Fabricated By Laser Cladding

AISI 304 stainless steel is widely used in machinery manufacturing industry because of its good toughness and excellent corrosion resistance.However,in the harsh environment,the contact surface of the key friction moving parts can not be lubricated and maintained in time,and the surface wear failure phenomenon is more serious,which not only shortens the service life of the workpiece,but also brings great security risks.In order to solve the problem of poor wear resistance of AISI 304stainless steel,a layer of wear-resistant coating was designed and prepared on the surface of AISI 304 stainless steel by laser cladding technology to improve the wear resistance of stainless steel.The key to the preparation of wear-resistant coating lies in the selection of materials and the design of surface structure.In this paper,AlCoCrFeNiSi high entropy alloy coating is cladding on the surface of AISI 304 stainless steel by laser cladding technology.Firstly,through theoretical analysis and practical operation,a group of optimal cladding process parameters are found to achieve a good metallurgical combination between the coating and the substrate,so that the coating can play the best performance（hardness,friction and wear,electrochemical corrosion,etc.）Then the effects of different Si content on the microstructure and properties of AlCoCrFeNi high entropy alloy coating were studied by means of XRD,SEM,EDS,TEM,microhardness tester and friction and wear tester.Finally,the laser cladding technology was used to prepare the texture coating of soft（AISI 304 stainless steel）and hard（high entropy alloy）interlaced stripes on the surface of AISI 304 stainless steel.The influence of hard unit material and distribution distance on the friction and wear properties of the texture coating was studied.It is found that when the laser energy density is 143 Jmm^-2,there is no crack on the surface of the high entropy alloy coating,and the good metallurgical bonding is achieved between the coating and the substrate The phase structure of AlCoCrFeNiSi_x high entropy alloy coating consists of disordered BCC Fe-Cr phase and ordered BCC AlNi nano phase.When the content of Si is 0.5,the hardness of high entropy alloy coating reaches the maximum value,and the average hardness is 821.5 HV_0.3.The main reason is that with the increase of Si,the effects of solution strengthening,dislocation strengthening and fine grain strengthening are obviously enhanced,among which dislocation strengthening contributes the most to the improvement of coating hardness.In the process of friction and wear,the coating with high Si content will form the oxide film of SiO₂ and SiO with lubricating effect,which has a great influence on the wear resistance and antifriction of the coating.In the electrochemical corrosion test,the corrosion resistance of the coating is improved with the increase of Si element.In the experiment of laser cladding surface texture coating,when the distribution spacing of hard unit is fixed（2.5 mm）,the wear resistance and antifriction of the surface texture coating increase with the hardness of the hard unit.When the hard unit material is fixed(Si_0.5),the wear resistance of the surface texture coating decreases with the increase of the distribution distance of the hard unit,while the antifriction increases with the increase of the distribution distance of the hard unit.There are 63 figures,16 tables and 95 references in this paper.