Research On The Forming Quality And Properties Of Laser Cladding AlCoCrFeNi High Entropy Alloy Coatin

The failure forms of mechanical parts such as wear,fatigue and corrosion often occur on the surface of the workpiece.Laser cladding is used to form a coating on the surface of the part with excellent characteristics such as high hardness,high wear resistance,corrosion resistance,and oxidation resistance.The coating can effectively reduce the wastage of the mechanical parts due to these failures.The high-entropy alloys possess excellent comprehensive properties.A high-entropy alloy coating can be prepared on the surface of the mechanical parts by laser cladding technology to enhance the surface properties of the parts to improve their service life.AlCoCrFeNi high-entropy alloys possess excellent wear resistance and corrosion resistance.However,their poor plasticity,low hardness and prone to cracks seriously affect the popularization and application of AlCoCrFeNi high-entropy alloys.In order to improve the surface forming performance of the cladding coating and reduce the internal defects of the coating,laser cladding coatings AlCoCrFeNi+x wt.%boron iron powder（x=3,4,5,6,7）and AlCoCrFeNi+x wt.%CeO₂high-entropy alloy coatings were prepared on the surface of 45 steel.The effect of boron iron powder and CeO₂addition on the forming quality,the microstructure,the hardness,the friction and the wear properties of AlCoCrFeNi high-entropy alloy coating were studied.After the optimization of the addition of boron iron powder and CeO₂,different content of Mo was added in the coating to improve its hardness,friction and wear properties.The results of the experiment are as follows:1.Nodules and cracks appear on the surface of AlCoCrFeNi high-entropy alloy coating without boron-iron powder.Adding 3-6 wt.%boron-iron powder can improve the surface quality of AlCoCrFeNi high-entropy alloy coating to a certain degrees.When 4 wt.%of boron iron powder is added,the cladding coating can obtain the best surface macro morphology,the crack defects are greatly reduced or even eliminated.The average hardness of the coating reaches 566.79±34.29 HV_0.5,the friction coefficient is reduced to 0.332±0.019 and the wear amount is reduced by 50%.2.The addition of 1.5 wt.%CeO₂ can reduce the spatter during the cladding process.It can also effectively reduce the cracks and improve the flatness on the surface of the high-entropy alloy cladding coatings.At the same time,the crystal grains can be significantly refined,and the uniformity of the cladding layer structure can be improved.With the addition of 0.5～4 wt.%CeO₂,the hardness of the cladding layer is slightly increased,up to 60 HV_0.5.The friction coefficient and the amount of wear loss of coating is reduced.Compared with the addition of boron-iron powder,the addition of CeO₂has a more obvious improvement effect on the forming quality of AlCoCrFeNi high-entropy alloy coatings.Therefore,the addition of CeO₂ is selected as the additive phase to improve the forming performance of the coating.3.The microstructure of AlCoCrFeNi Mox coating is refined.When x=0.3,the structure of the cladding coating changes from BCC phase to a mixed phase of BCC and FCC.When x=0.4,clear precipitates rich in Cr and Mo can be observed,x=0.5,the hardness increase is most obvious,the surface average hardness reaches 756 HV_0.5,the friction coefficient is reduced to 0.191,the amount of wear has been reduced by approximately 58%,and the mechanical properties are greatly improved compared with AlCoCrFeNi coating.