The Research On Laser Cladding Co-based Coating On 316L Stainless Steel And Its Corrosion Resistance In Liquid Pb-Bi

Lead-bismuth eutectic alloy?LBE?has the advantages of low melting,high boiling and high thermal conductivity,etc.It is also used as a coolant and spalling target material for lead-cooled fast reactors and accelerator subcritical drive systems.In the cooling system,in addition to a large number of neutrons irradiating the structural materials,the flowing state of LBE not only causes oxidative corrosion and dissolution corrosion to metal materials,but also produces certain friction and wear on the materials due to the scouring effect,which greatly affects the cooling system.The performance of the material.Laser cladding technology can prepare a coating with good performance on the surface of the base material and improve the overall performance.In this paper,laser melting technology is used to strengthen the surface of steel materials to improve the service life of nuclear reactor components.Using316L,which is commonly used in nuclear structures,as the matrix material,a laser cladding coating is prepared on its surface,and the coating is resistant to corrosion in liquid LBE Research on wear resistance provides test data and theoretical guidance for improving the service life of nuclear components.This article was used laser cladding technology first,optimizes the process parameters through orthogonal experiments,and prepares a layer of Stellite6 coating on the surface of 316L stainless steel in multiple laps.In order to improve wear resistance,different levels of WC are used as the coating reinforcement phase.Using a high-temperature lead-bismuth melting furnace independently designed by the research group to conduct a corrosion test at 400?,the effect of liquid LBE at different relative flow rates on the corrosion behavior of Stellite6 cladding layer was studied,and the cladding coatings with different WC contents were investigated The influence law of corrosion behavior in liquid LBE.Co-based coating prepared by cladding process parameters of laser power 1800W,laser scanning speed 500 mm/min,powder feed volume 11.8g/min,spot diameter3 mm,overlap rate 50%,found the bottom structure of Stellite6 is a plane crystal and a cell crystal,the middle structure is a cell crystal and a dendrite,the top structure is an equiaxed crystal,and the crystal grains at multiple overlaps grow along different directions.The phase composition of the coating is mainly?-Co,CoCx,?Cr,Fe?₇C₃and M₂₃C₆.The?-Co solid solution matrix of the cobalt-based coating is distributed with a multi-element eutectic structure.The eutectic structure contains a large number of compounds such as CoCx,?Cr,Fe?₇C₃ and M₂₃C₆.The hardness value of Stellite6coating is about 2.3 times that of the substrate.With the increase of WC content,the hardness value of the coating surface is also higher.At 400?,after the liquid LBE of different relative velocities?0 m/s,2.18 m/s,2.56 m/s,3.23 m/s?corroded for 1500 h,the oxidation and dissolution corrosion of the Stellite6 coating all occurred The amount of oxide is Fe₃O₄,and a certain amount of O element diffuses into the coating.With the increase of the relative flow velocity,the surface roughness value of the Co-based coating sample also gradually increased.When the flow velocity is 3.23 m/s,the roughness value is maximum Sa=49.84?m;with the increase of the relative flow velocity,The depth of the oxygen-permeable layer on the surface of the Stellite6 cladding layer gradually increased,and the depth of the oxygen-permeable layer was 5.2?m at the velocity of 3.23 m/s.Adding different WC content?0,5%,10%,15%?to Stellite6 powder,the Co-based coating prepared by liquid LBE has different corrosion resistance.With the increase of WC content,its surface roughness and oxygen permeability The layer depth gradually increases.When the WC content is 10%,the surface quality is the best;as the WC content continues to increase to 15%,the surface quality decreases instead,and the roughness and oxygenated layer depth increase.As the corrosion time increases,the dissolution of the elements on the sample surface and LBE intensifies,resulting in a progressive increase in the depth of the oxygenated layer on the coating surface.The 316L stainless steel has many corrosion pits on the surface after long-term corrosion,and serious oxidative corrosion,dissolution corrosion and abrasion have occurred.