Study On Microstructure And Wear Resistance Of Plasma Sprayed WC/Fe Coating By Laser Remelting

Mechanical equipment often operates under complex and harsh conditions,such as variable load,wear,impact,and corrosion.The requirements for mechanical components is becoming more and more stricter.45 carbon steel is a high-quality carbon steel which is widely used in various industrial fields,but its performance has been difficult to meet the needs of industrial development.The plasma spraying technology can prepare the modified and wear-resistant coating quickly and efficiently.It is one of the most effective technologies to prepare the wear-resistant metal ceramic coating.However,there are defects in plasma sprayed coatings such as tissue evacuation,instability of coating and matrix,low cohesion strength,which restrict the development of excellent wear resistance of hard ceramic materials seriously.Laser remelting technology can quickly melt and solidify the surface of the material,so as to obtain the surface with high cohesive strength and excellent wear resistance.In this paper,a plasma sprayed WC/Fe composite ceramic coating was prepared on the surface of 45 steel,and then the coating was remelted by laser remelting.The influence of laser power and scanning speed on microstructure and wear resistance of plasma remelting coating was discussed.The parameters of laser remelting process were optimized by orthogonal test.Plasma laser remelting coatings were prepared by optimized process parameters.The influence of laser remelting on microstructure of plasma sprayed coatings was discussed,and the improving mechanism of laser remelting on wear resistant of plasma sprayed coatings was also discussed.The microstructure characteristics,phase composition and microhardness of plasma spraying coating and laser remelted coating were characterized by scanning electron microscopy（SEM）,X ray diffraction（XRD）,microhardness tester.The wear resistant of plasma spraying coating and laser remelted coating was tested by wear test machine,and the wear resistant mechanism was also analyzed.The following conclusions are obtained:（1）The microstructure of plasma remelting coating with laser power of 800W is the most uniform and compact microstructure,and its wear volume is the smallest,showing the most excellent wear resistance.The plasma laser remelting coating with scanning speed of150mm/min has the best wear resistance.Through orthogonal test,the optimal technological parameters for the laser remelting laser power are 650W,scanning speed of 250mm/min,spot diameter of 4mm and overlap ratio 30%,pulse width is 4.4ms,the average microhardness and the optimal parameters for preparation of remelting coating is 1266HV,the wear volume is29.45mg.（2）The laser remelting plasma sprayed coatings produced melting and recrystallization,the surface roughness,microstructure of coating is uniform and dense,M₂₃C₆ generated carbon compounds,（Cr,Ni）₃Si and Ni₆BSi₂ hard phase improves the hardness of the coating,the average micro hardness of about 1500HV.（3）After laser remelting,the hard ceramic phase produced in the coating played a role of dispersion strengthening,which increased the wear resistance of the plasma sprayed coating,and there was only slight scratch on the worn surface of the laser remelted coating.