Study On Microstructure And Properties Of WC/Ni60 Composite Coating By Alternating Magnetic Field Assisted Laser Cladding

Adding a certain amount of WC particles in the laser cladded powder is currently one of the most direct and effective means to improve the performance of the cladding layer.However,the accumulation of WC particles often occurs at the bottom of cladding layer,thus inhibiting the optimization of mechanical properties and resulting in stress concentration and coating cracking.In response to it,this paper proposes to prepare the WC/Ni60 composite coating by alternating magnetic field assisted laser cladding based on the research object of 45 steel substrate-WC/Ni60 composite coating,by means of optimizing processing approach.The effect of the alternating magnetic field on the solidification process of the laser pool is investigated.The effect of the alternating magnetic field on the distribution of hard phase particles,macroscopic morphology,microstructure morphology,and phase composition of the cladded WC is studied.The major contents and conclusions are as follows:The processing parameters of laser cladding are initially optimized before the alternating magnetic field coupling experiment.And the alternating magnetic field is proposed to be applied in the laser cladding process so as to resolve the WC particle accumulation and optimize properties of the cladding layer.And the effect of alternating magnetic field on the material and heat transfer is investigated.By means of a magnetic field generator,the effect of the alternating magnetic field on the WC particle distribution,macrostructure and microstructure,phase composition,microhardness,tribological properties and corrosive resistance of the laser cladding layer is investigated.By analyzing the effect of the alternating magnetic field on the laser pool,it is discovered that applying the alternating magnetic field can significantly affect the macroscopic morphology of the cladding layer and inhibit the columnar crystal growth at the coating bottom.The research results are as follows: The alternating magnetic field can significantly impact the distribution of WC particles in the cross-section of the cladding layer.Under the application of the alternating magnetic field,WC particles at the bottom are stirred and dispersed to the middle and upper area of the laser pool.The cladding layer decreases in height,exhibits slight variations in width,and barely affects the dilution ratio.The composition of laser cladding layer is barely altered with the application of alternating magnetic field.The main composition of the WC/Ni60 composite coating is dominated by γ-Ni(Fe)solid solution,as well as composite carbides and borides,such as Cr23C6,Cr7C3,Cr5B3,Ni C,WC,and W2 C.The precipitation of the carbide hard phase in the cladding layer is increased with the application of the alternating magnetic field.In the absence of the alternating magnetic field,the coating microhardness is 755.2HV0.2.The microhardness at the magnetic field intensity of 40 m T is 820.3 HV0.2,which is 8.62% higher than that without magnetic field.Yhe wear amount is on the decline with the increasing intensity of alternating magnetic field.In the absence of alternating magnetic field,the wear loss is about 14.22×10-4g.When the magnetic field intensity is 40 m T,the wear loss only accounts for 7.35×10-4g,which is 48%lower than that without magnetic field.The alternating magnetic field improves the corrosive resistance of the cladding layer.The corrosion rate is reduced by 21.37% when the intensity of alternating magnetic field is 40 m T,compared with that without the magnetic field.