Effect of Si Content on Microstructure and High Temperature Friction Properties of FeCrNiCSix Coating by Laser Cladding
After the key parts of metallurgical equipment are used in high temperature environment for a long time,the surface is easy to be damaged.In high temperature environment,the Fe-Cr-Si alloy coating can protect the substrate from high temperature gases,oxides and corrosive media,while providing high hardness and wear resistance.Therefore,it is widely used for surface protection of service parts in high temperature,high corrosion and high wear environments.At present,the main research pays more attention to Fe-Cr-Si coatings with low Si content,and less to Fe-Cr-Si coatings with high Si content.The coating prepared by laser cladding technology has the advantages of metallurgical bonding,low dilution rate,small heat-affected zone and dense microstructure.The preparation of protective coating by laser cladding technology is a suitable way to improve the service life of parts.The work aims to solve the problem of surface failure of metallurgical parts in high temperature environment and investigate the effect of Si content on the high temperature wear performance of Fe-based coatings.Therefore,chromium powder,silicon powder,nickel powder,carbon powder and iron powder(purity≥99%)were used to prepare alloy powder.The Si content of the alloy powder was 5%,10%and 15%.The finished powder was mixed with a star ball mill.After mixing,the powder was dried in a vacuum drying oven at 100℃for 2 h.The process parameters of laser cladding were as follows:laser power of 1 600 W,lap rate of 50%,spot diameter of 5 mm,scanning speed of 600 mm/min and powder feeding speed of 5 r/min.The base material was 1Cr11Ni2W2MoV heat-resistant steel plate.The phase composition of the coating was analyzed by X-ray diffractometer.The microstructure of the coating and its element distribution were analyzed by scanning electron microscope(SEM)and its own energy dispersive spectrometer(EDS).The friction and wear properties of coatings with different Si contents were tested by friction and wear testing machine at 500℃,and the friction coefficient curve and wear mechanism of coatings were analyzed.Si could improve the oxidation resistance of the coating and refine the grain.With the increase of Si content,the coating produced Fe3Si phase,the microhardness increased,the friction coefficient decreased,and the wear rate increased.The reason for the increase of coating wear rate was that Fe3Si had phase brittleness,so the degree of spalling was larger.The phase of 5%Si coating was γ-Fe and Fe-Cr solid solution,and the microstructure was mainly isometric crystal and dendrite,the average microhardness was 304.3HV0.5,the average friction coefficient was 0.61,the wear rate was 3.10×10-5 g/m,and the wear form was mainly adhesive wear.The phase of 10%Si and 15%Si coatings was Fe3Si and Fe-Cr solid solution,the microstructure was mainly equiaxial and the wear form was mainly spalling wear.The average microhardness of 10%Si coating was 576.6HV0.5,the average friction coefficient was 0.50,and the wear rate was 5.90×10-5 g/m.The average microhardness of 15%coating was 598.5HV0.5,the average friction coefficient was 0.47,and the wear rate was 7.39×10-5 g/m.
laser claddingFe-Cr-Si alloymicrostructuremicrohardnesshigh temperature friction wearwear mechanism
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