MIG Additive Manufacturing Of Stainless Steel Wire And Laser Multi-phase Processing

With the improvement of the level of economic developments,the development of various fields had put forward higher requirements for the applicability of materials in different working environments,such as daily necessities processing,aerospace and military enterprises and the other manufacturing industries.In view of the disadvantages of the stainless steel additive manufacturing materials,such as low hardness and poor wear resistance,surface performance of the stainless steel should be modified.The Co base alloy powders have been widely used in the industrial productions.The alloy powders have good wettability and wear resistance,which could significantly improve the wear resistance of the substrate;addition of Cu could refine the microstructure of the laser clad layer,playing a role in leading the precipitates to be produced at the grain boundaries,favoring to increase the hardness of the fabricated materials;Ag-added could accelerate formations of the precipitates also refine the microstructure.In this paper,the arc additive manufacturing and laser multi-phase processing technology were used to prepare the Co 800-Si C-Cu-Ag clad layer on the additive manufacturing 316L stainless steel to strengthen the surface performance of the substrate.This paper was divided into three parts:the deposited layers by MIG additive manufacturing were prepared,the best process parameter can be selected,the stainless steel samples under the different process parameters were prepared,measuring the micro-hardness of the samples,indicating that the micro-hardness of the laser re-melted layer was high.XRD and EDS were used to analyze the phase constituent and the element distribution of the samples.The microstructure of the 316L stainless steel samples under the parameters of the current 120 A,the voltage 17.7 V,and deposition speed 3 mm/s was good.After the sample was processed,the mixed powders pre-placed on substrate surface were processed by the laser cladding according to the predetermined processing route,the samples prepared with different powders and the process parameters were grouped,also the microstructure was observed.The precipitates were formed due to Cu-added,stabilizing the grain boundaries and refining the grain sizes,enhancing the micro-hardness of the laser clad layers;the precipitations of the strengthening phases was accelerated by the Ag-added,enhancing the micro-hardness of the laser clad layers;the number of the pore defects in the microstructure in re-melting layer significantly reduced.In addition,the micro-hardness of the laser re-melting layer was higher than the clad layer free of the re-melting.The Co base clad layer was analyzed,the HRTEM image showed that the amorphous/nanocrystalline phases were formed in the clad layer after additions of Cu and Ag,and the nanoscale crystals gathered at the grain boundaries to play a pinning role,stabilizing the grain boundary.The studies showed that the Co_0.52Cu_0.48phase grows along the(111),(200),(220)crystal planes as a result of the compound formed by the combination of Co and Cu in a puddle could not fully grow up,favoring the nanocrystalline phases to be formed,resulting in the lattice distortions.The isotropic characteristics of the amorphous phases had a positive effect on the pressure and friction.The formation of the nanocrystalline phases favored to enhance the wear resistance of the clad layer,which can be formed after the multi-phase treatments.The various phases were beneficial to improve surface performance of the laser clad layer.The SEM images showed that the microstructure of the clad layer can be refined with the additions of Cu and Ag.The analysis showed that some elements distributed uniformly in the laser clad layer,also multi-phase can be formed.The friction and wear experiments showed that the fabricated clad layer significantly improved the wear resistance of the additive manufacturing stainless steel surface.In this study,the clad layers were fabricated on the additive manufacturing stainless steel substrate by the laser cladding to improve the surface performance of the substrate,which had the certain theoretical value to expand the laser processing technology and the stainless steel to be used in the fields of the medical equipment,the aerospace also the other fields.