Study On Microstructure Evolution And Mechanical Properties Of Nickel-Based Superalloy Coating By Laser Cladding On Compacted Graphite Cast Iron

Compacted graphite cast iron has been widely used in automobile manufacturing and natural gas industry,et.al.It is a high-quality material to manufacture cylinder blocks,cylinder heads,cylinder liners and other components.However,as the engine develops in the direction of high power and large size,it is important to improve the hardness and wear resistance of compacted graphite cast iron.Laser cladding has the advantages of high cooling rate,small heat input,small thermal deformation of the substrate,and low energy consumption.At the same time,nickel-based self-fluxing alloy powder has the advantages of good toughness and abrasion resistance,and has self-lubricating effect at high temperature.Therefore,three types of nickel-based alloy cladding layers,Ni60A+35wt%WC,Ni60A+35wt%WC+0.5wt%CeO2,Ni60A+35wt%WC+1wt%CeO2,were prepared on the surface of compacted graphite cast iron using laser cladding technology.The effects of laser cladding experimental parameters and high temperature heat treatment on the microstructure and mechanical properties of the cladding layer were investigated.The influence of laser power and scanning speed on the microstructure,microhardness,wear resistance and corrosion resistance of the cladding layer is studied in this paper.The results show that as the laser power decreases and the scanning speed increases,the microstructure is gradually refined and uniform,the hardness of the cladding layer is increased,and the wear resistance of the cladding layer is increased.In addition,the corrosion resistance of the cladding layer is enhanced.The effect of the thickness of the preset coating and the amount of CeO₂ powder on the microstructure and microhardness,wear resistance of the cladding layer was also studied in this paper.The results show that as the thickness of the preset coating increases,the microstructure tends to be coarsened,and the hardness is also significantly reduced and the wear resistance of the cladding layer is decreased;the CeO2 powder can effectively refine the structure of the cladding layer,thereby increasing the hardness of the cladding layer,but research shows that in the case of the preset coating is thinner and the scanning speed is smaller,the addition amount of CeO₂ powder should not exceed 0.5%.Finally,the cladding layer was subjected to high-temperature heating treatment at different temperatures.The effects of heating temperature on the microstructure,hardness and Wear resistance of the cladding layer are investigated.The results show that the high-temperature heating treatment can refine the microstructure and the hardness is increased,and the wear resistance of the cladding layer is increased.However,if the heating temperature is too high,it will also have the opposite effect.Under this experimental condition,the high-temperature heat treatment temperature of the cladding layer should not exceed 800?.