Research On Laser Clad Fe-based Coating And Its Wear Resistance

Laser cladding technology includes the research of structure and properties of Co-based,Ni-based and Fe-based alloys after cladding on metal surface.Compared with Co-based and Ni-based self-fluxing alloy powders,Fe-based self-fluxing alloy powders are suitable for parts requiring local wear resistance and easy deformation.And the powder has the advantage that needs low cost and has a good wear resistance.However,comparing with Ni-based and Co-based coatings,the structure of Fe-based coating is more complex and has more crack.Composition and laser processing parameters of the cladding have a great influence on the structure of the coating.Therefore,the research on laser cladding for preparing Fe-based coating reinforced nodular cast iron mould will be of great significance.Laserline LDF4000-60 laser was used in this experiment,and the key process parameters were controlled by the way of equiaxed synchronous powder feeding.Laser cladding layers with different microstructures and properties were prepared through comprehensive experiments.In this paper,three parameters,laser power,powder feeding quantity and scanning speed,were selected in a reasonable range.The research on laser cladding of Fe-based coating for strengthening nodular cast iron mould was carried out.The experimental results show that the Fe-based coating prepared by laser cladding can achieve crack-free,and has good bonding with the matrix.The hardness and wear resistance of nodular cast iron are greatly improved by Fe-based coating.The dependence of laser power,powder feeding quantity and scanning speed on the height,width and dilution of the coating was studied.Based on the measurement and calculation,and combined with the results of correlation analysis,the processing map of laser cladding was drawn.A reasonable laser processing interval was given.Cracks sensitivity increases when dilution ratio is more than 20%,and poor bonding between coating and matrix happens when dilution ratio is less than 5%.The optimum dilution zone is between 5% and 20%.In actual production,the parameters such as laser power,powder feeding quantity and scanning speed can be reasonably selected by combining with the processing map to obtain a reasonable coating.The effect of laser power on the structure and hardness of the coatings was studied.The results show that the dilution rate increases with the increase of laser power.And the plane and cell crystal regions decrease,the columnar dendrite,equiaxed dendrite regions are widened,and the grain growth is more sufficient with the increase of laser power.Retained austenite increases,martensite decreases,the hardness of the coating increases first and then decreases with the increase of laser power.The effect of scanning speed on the structure,hardness and crack sensitivity of the coatings were studied.The results show that the dilution decreases,the plane crystal,the cell crystal region are widened,the columnar dendrite region and the equiaxed dendrite region narrows with the increase of scanning speed.Martensite increases and retained austenite decreases with the increase of scanning speed,.The hardness increases and solidification cracks tend to occur at low scanning speed.The effect of powder feeding quantity on the structure and hardness of coatings was studied.It is found that the dilution decreases,the plane and cell crystal regions of the coatings are widened,and the columnar dendrite regions are narrowed.with the increase of powder feeding quantity.When the powder feeding quantity increases to a certain value,the equiaxed dendrite regions disappear.Martensite increases and retained austenite decreases with the increase of powder feeding quantity.The hardness increases and then decreasesThe micro-wear properties of the coatings at different laser power under 0.2 N and 1 N loads were studied,and the effects of the coatings with different structures on the wear resistance were discussed.Under 0.2 N load,the wear loss is very low and the wear resistance is good under different laser power.There is no obvious difference in the performance of the coatings.Under 1 N load,the coatings with different laser power exhibit the characteristics of adhesive wear.Within the range of experimental parameters,the smaller of the power,the better of the wear resistance.The wear resistance increases gradually with the increase of martensite content of the coating.