Mo含量对激光熔覆CoCrFeNiW0.6Mox高熵合金涂层组织与性能的影响OA北大核心CSTPCD

The work aims to study the effect of Mo content on laser cladding CoCrFeNiW0.6 high entropy alloy coating.CoCrFeNiW0.6Mox(x= 0,0.2,0.4,0.6,0.8)high entropy alloy coating was prepared on the surface of 45 steel by RFL-C1000 fiber laser.The CoCrFeNi alloy powder,pure W powder and pure Mo powder in molar ratio were weighed by JA2003 electronic precision scale,and the alloy powder was evenly mixed by MSK-SFM-1 horizontal planetary ball mill.Then,the mixed powder was dried in a drying oven for 2 h and put into a sealed bag for later use.The 45 steel was cut into 50 mm×50 mm×10 mm and 25 mm×50 mm×10 mm sample blocks by spark cutting machine,which were respectively used for laser multi-channel and single-channel cladding.The oxide skin was removed by grinding with 240-1 200 purpose sandpaper in turn,and then polished until the surface was smooth.The substrate was cleaned in the ultrasonic cleaning machine to remove surface impurities and dried with cold air and placed in a drying dish until ready to use.The pre-coated laser cladding method was used for single and multi-channel cladding on the cut sample block,then the sample was cut by a wire cutter,the cross section was polished,and the saturated ferric chloride hydrochloric acid etchants were used to etch the sample.The morphology and dilution rate of the cladding layer were observed and analyzed by Leica DVM6 optical microscope.HITACHI TM3030 scanning electron microscope(SEM)was used to observe the microstructure of the cladding layer,and energy dispersive spectrometer(EDS)was used to test and analyze the distribution of elements in the cladding layer.D8 X-ray diffractometer was used to analyze the phase structure of the cladding layer.Microhardness test of single cladding layer was carried out by HV1000Z automatic turret microhardness tester.Lk2010 electrochemical workstation was used to conduct electrochemical corrosion on the coating,and the corrosion resistance was analyzed by the Tafel curve obtained.The results showed that the binding state and surface morphology of the coating were good after the addition of Mo element.When x=0-0.4,the microstructure of the coating was mainly dendritic,and the grain became finer gradually.When x≥0.6,cracks appeared on the coating surface.With the addition of Mo element,σ phase was precipitated gradually,and the grain size decreased gradually.When x=0.8,eutectic structure was formed.The microhardness of the coating increased with the increase of Mo element,but because more cracks appeared at x=0.8,the appearance of cracks affected the hardness of the coating,resulting in a decrease of hardness at x=0.8.When x=0.6,the average microhardness of the coating reached 959.69HV0.3,about 20.32% of the average hardness of CoCrFeNiW0.6 coating.When x=0-0.6,the corrosion resistance of the coating gradually increased with the increase of Mo element content.When x=0.8,the corrosion resistance of the coating deteriorated,which was due to the appearance of cracks and the formation of σ phase.When x=0.6,the corrosion resistance of the coating was the best.It can be concluded that the addition of Mo element makes the microstructure of the coating appear σ phase,which can significantly improve the hardness and corrosion resistance of the coating.The strengthening mechanisms are fine crystal strengthening,solid solution strengthening and second phase(σ phase)strengthening.