Study On The Effect Of Electromagnetic Composite Field On The Distribution Of Pore And WC Particles In Cladding Layer

As a new additive manufacturing technology,laser cladding technology has been widely used in important fields of aerospace,shipbuilding,nuclear power and energy chemical industry.The ideal distribution of pores and hard phases is a common problem in laser cladding processes,which can seriously affect the physical properties and reliability of cladding materials.In this paper,the electro-magnetic compound field is added to the laser cladding process to change the volumetric force state of the molten pool,and finally the improvement of the pore and hard phase distribution is achieved.In this paper,the influence of the electro-magnetic compound field on the force state of the molten pool is achieved,and the purpose of regulating the distribution of the pores in the molten pool is achieved.The effects of electro-magnetic compound field on the macroscopic morphology and pore distribution of laser cladding layer were investigated.In the experiment,92%AISI 316L and 8%TiH₂ laser cladding powder were used to obtain a stable pore distribution.Studies have shown that when applying the downward Ampere force to the molten pool,both porosity and pore radius decrease with the increase of the direct current.The pore distribution is concentrated toward the upper surface of the cladding layer.When the current is120A,the porosity is reduced by 64.71%.When the upward Ampere force is applied,both the porosity and the pore radius increase with the increase of the direct current.The pore distribution of the cladding layer is more uniform along along the vertical direction.When the direct current to the substrate is-90 A,the porosity is increased by 144%.The changes of morphology,microstructure and microhardness of the cladding layer under different Ampere forces were analyzed.Studies have shown that the height of the cladding layer decreases with the increase of the ampere force in the direction of gravity.When the basic process parameters were kept constant,there was no significant difference in grain size,grain characteristics and hardness between the different samples.In this paper,the influence of the electro-magnetic compound field on the force state of the molten pool is achieved,and the purpose of regulating the distribution of WC particles in the molten pool is achieved.The effects of electro-magnetic compound field on the macroscopic morphology of laser cladding layer and the distribution of WC particles were investigated.Studies have shown that when applying downward Ampere force,the distribution of WC particles in the cladding layer tends to accumulate toward the upper surface of the cladding layer.The content of WC particles in the lower half of the cladding layer was 19%,and the content of WC particles in the upper half of the cladding layer was 81%.The WC particles are easily brought to the solidification boundary of the molten pool by the molten pool fluid,and the WC particles hardly sink to the bottom of the molten pool in premature curing,and the WC particles are more likely to remain in the upper half part of the cladding layer.When upward Ampere force is applied,the distribution of WC particles in the cladding layer exhibits a tendency to gradually increase from the surface layer to the bottom portion.The content of WC particles in the lower half of the cladding layer was 59%,and the content of WC particles in the upper half of the cladding layer was 41%.The rate at which the WC particles sink in the bath increases,making it easier for the WC particles to enter the bottom of the bath to be solidified.The microstructure and microhardness of the cladding layer when WC particles were added to the cladding layer were investigated.Studies have shown that the upper part of the cladding layer is equiaxed,the middle part is refined dendrites,and the junction between the substrate and the cladding layer is coarse dendrites and planar crystals.Due to the presence of WC particles in the cladding layer,the dendrites epitaxially grown from the bottom of the cladding layer in the middle of the cladding layer are epitaxially grown with WC particles as nucleus,and the dendrite grain size here is smaller than the bottom of the cladding layer.The hardness of the substrate is about 180 HV,and the hardness of the cladding layer is increased to more than twice the hardness of the substrate after the addition of the WC particles.When the downward Ampere force is applied to the molten pool,the hardness gradually decreases from the upper surface to the substrate in the cladding layer.When the upward Ampere force is applied to the molten pool,the change in the hardness of the cladding layer is reversed.