Investigation On Microstructure And Properties Of Laser Cladding Fe-Al-Ti-WC Coatings On High Speed Steel

High speed steel occupies a large market share in the current tool market due to its good process performance,good strength and toughness.It is widely used in various mechanical processing scenes.At the same time,in engineering applications,high-speed steel cutters have failure phenomena such as wear,stress corrosion and fatigue damage.Especially when the processing conditions are relatively harsh,the hardness and high temperature performance of high-speed steel tools are difficult to meet the processing requirements.Thereby reducing production efficiency.Therefore,it is very necessary to optimize the performance of commonly used high-speed steel tools.By adjusting the alloy material composition or improving the tool structure to improve the tool performance,it is not only difficult but also costly.As a mature surface modification technology,laser cladding technology can not only improve the performance of cutting tools,but also reduce the consumption of tools as a tool repairing method.In this paper,the advantages of laser cladding technology are used,and Fe-Al-Ti-WC composite powder is used to study the new type of tool coating on the surface of high-speed steel.The main research work completed is as follows:(1)By setting up a single factor test,the influence of laser process parameters(including:laser power,scanning speed,powder feeding speed,overlap rate)on the melting of multiple cladding layers and the surface morphology was studied.The results show that the degree of melting of the cladding layer is mainly affected by the laser power and scanning speed,and the surface morphology of the cladding layer is affected by various process parameters.Based on the better process parameter range obtained by the single factor test,an orthogonal test was designed to comprehensively evaluate the surface morphology,microhardness,crack rate and porosity of the cladding layer.The optimal laser process parameters obtained from the analysis are:laser power P=1.0 k W,scanning speed V₁=350mm/min,powder feeding speed V₂=50 L/min,and overlap rate of 40%.(2)Using optical microscope(OM),scanning electron microscope(SEM),X-ray diffractometer(XRD),energy spectrum analyzer(EDS)and micro hardness tester to prepare the cladding layer and substrate at different overlap rates respectively The metallurgical bonding state,phase composition,microstructure,and microhardness were analyzed and tested.The results show that under the optimized process parameters,the cladding layer prepared at the overlap rate of40%and the substrate are in a good metallurgical bonding state,and the hard phases such as WC and in-situ generated Ti C and Al₂O₃ are dispersed in the coating Most of the hard phase exists inside the grains and on the grain boundaries,and plays the role of refining the grains;the hardness of the cladding layer is distributed in a gradient,and the average microhardness is HV 1309,which is about twice that of the matrix.With the increase of the overlap rate of multiple cladding layers,the phase composition of the cladding layer is basically unchanged;too low overlap rate affects the overall morphology of the cladding layer,too higher overlap rate will make the cladding Layer performance is reduced.(3)By studying the structure and performance of the cladding layer under different Al contents,the results show that there are a large number of pores and cracks inside the cladding layer without Al addition,the internal structure is loose,and the structure distribution is uneven;the Al content added is At 20 wt%,the pores and cracks in the cladding layer were significantly reduced,and the microhardness reached the expected requirements;when the Al powder content in the composite powder was further increased to 30 wt%,the microhardness of the cladding layer decreased significantly and was lower than that of high-speed steel The microhardness of the substrate.(4)A dry sliding friction and wear test(at room temperature)was performed on the cladding layers prepared under different overlap rates and different Al contents using a comprehensive surface performance tester,and the wear marks were observed and analyzed using scanning electron microscope(SEM).The results show that as the overlap rate increases,the average friction factor of the cladding layer increases first and then decreases;the wear mechanism of the cladding layer gradually changes from adhesive wear and abrasive grain wear to delamination wear,when the lap rate is 40%The abrasion resistance of the cladding layer is improved by 3.5 times compared with the substrate.The cladding layer that does not contain Al is mainly peeling type wear,and its wear surface has many cracks,and the brittle fall off is serious during the test;when the Al content is 20wt%,the wear form of the cladding layer is also mainly peeling type wear,but The wear surface rules are complete and the amount of wear is very small;continue to increase the content of Al in the cladding layer,the wear mechanism of the cladding layer changes to adhesive wear and abrasive wear,the amount of wear increases,and the wear resistance decreases.(5)Using an electrochemical workstation,electrochemical corrosion tests were performed on multiple overlap cladding layers prepared under different overlap rates and different Al contents.The results shows:The corrosion resistance of the cladding layer increased first and then decreased with the increase of the overlap rate;as the Al content increased,the corrosion resistance of the cladding layer also increased relatively.