| Stainless Steel is important material in the pump manufacturing.So it is an extremely important issue to improve the hardness and wear resistance of Stainless Steel without reducing the corrosion resistance.Plasma transferred arc welding/laser cladding technology is an advanced surface strengthening method,and they can form the coatings with good microstructure.But sometimes changing welding parameters or alloy powder composition can not meet the requirements.The magnetic field is applied during plasma transferred arc welding/laser cladding process at this time,to obtain requiring microstructure and properties,so their application is gradually being taken seriously.In this paper,Fe90/WC_P composite coatings were prepared by different processes,and microstructure and properties were studied.Microstructure of the coatings was observed using optical microscope(OM)and transmission electron microscope(TEM);phase analysis of the coatings was detected using X-ray diffractometer(XRD);chemical composition of the coatings was analyzed using scanning electron microscope(SEM)and electron probe microanalysis(EPMA);hardness of the coatings was detected using Vickers and Rockwell hardness test;abrasion resistance was detected using friction and wear test;electrochemical corrosion was detected using CS300 electrochemical zeta potential scanner.Research indicates:(1)Fe90 coatings obtained by plasma transferred arc welding process under different welding currents are composed of martensite and carbon boron compounds such as(Cr,Fe)7C3,CrFeB,Cr B and Fe3 Si.When the welding current is 130 A,microstructure of the coatings is fine and uniform,the hardness is highest,the wear resistance is best.With the welding current increasing,the size of dendrites of the coatings becomes larger,feather-like interdendrites decrease,dot-like and striped interdendrites increase,the hardness and wear resistance of the coatings decrease,the corrosion resistance is basically unchanged.(2)Fe90/WC_P composite coatings obtained by plasma transferred arc welding process under different tungsten carbide content are consisted of martensite,austenite and hard phase(Cr,Fe)7C3,WC,W2 C,lamellar(Fe,W)6C,reticulated(Cr,Fe)23C6 and long blocks Cr3C2.The dissolution of tungsten carbide and take an reaction with iron-based alloying elements,which forms lamellar and irregular lumps containing elongated pores eutectic structure.With the increasement of tungsten carbide content,dendrites size decreases,and undissolved tungsten carbide particles appear "sink bottom" phenomenon.Adding the tungsten carbide hard particles to the Fe90 alloy powder can improve the wear and corrosion resistance of the coatings.However,in order to ensure that the coatings have better wear resistance and corrosion resistance at the same time,it is should be consider content of tungsten carbide and distance from the fusion line.(3)Fe90 coatings obtained by the magnetic field applied during laser cladding process are consisted of martensite matrix and Cr7C3 carbide,CrFeB and Fe2 B borides.Cr and Si element are soluted in the martensite matrix.All of B element is aggregated in the interdendrites to form the network block Fe2 B compounds.Carbides are composed of granular Cr7C3 carbides dispersed on the martensite matrix and long crusty Cr7C3 carbides.When the laser power is 1200 W and the magnetic flux density is 0.05 T,the best microstructure is obtained,and the microhardness is highest and reaches to 822.80 HV. |
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