Optimization of Porosity and Microstructure Analysis in Laser-clad C276 Coating on Ductile Iron Surface

ZHANG Hao; LI Dasheng

doi:10.19329/j.cnki.1673-2928.2025.02.010

Abstract：To improve the corrosion resistance of ductile iron surface,a C276 coating was prepared on the surface of ductile iron by laser cladding technology.Macroscopic cross-sectional morphology was observed by using a metallurgical microscope.Using Box-Behnken design and single factor experiments,the relationship between porosity and process parameters was studied.Through comparative experiments,the influence of different types of laser sources on the porosity of coatings was explored.The microstructure of coating cross-section was studied by using corrosive solution for corrosion.The results indicate that determining the range of scanning speed Vs has a higher priority compared to laser power P and powder feeding rate Vt.Gaussian laser source can effectively reduce the heat input of the substrate in the overlapping area,thereby suppressing the generation of pores at the overlapping area and eliminating the phenomenon of pore enrichment.The average porosity of the coating with parameter A decreased from 0.08％to 0.023％,and that of the coating with parameter B decreased from 0.123％to 0.017％.Initial determination of the scanning speed,followed by determination of the laser power and powder feeding rate,and finally fine adjustment of the scanning speed are feasible methods for optimizing the porosity of laser cladding coatings on the surface of ductile iron.The optimal solutions of parameters P、Vs、Vt obtained from optimization are 1 000 W,10 mm/s,0.6 r/min and 1 300 W,10 mm/s,0.8 r/min.The average porosity of the cross-section is 0.023％and 0.017％,respectively,and the average coating thickness is 0.5 mm and 1.2 mm,respectively.The coating grains are composed of planar grains,cellular grains,columnar grains,and equiaxed grains in sequence.The continuous and sheet-like white microstructure is suppressed,and the overall grain size of the coating is small.The large number of refined equiaxed grains at the top improves the corrosion resistance of the coating.