Research On Hypereutectic Fe-Cr-Ni-C Wear Resistant Coatings By Plasma Cladding

The hypereutectic Fe-Cr-C coatings can exhibit high wear resistance under soft abrasive wear conditions,which are widely used in mining,metallurgy,construction and chemical industries because of the heat resistance,corrosion resistance and oxidation resistance,while the wear resistance of the coatings under hard abrasive and complex abrasive wear conditions is poor.In order to improve the wear resistance of hypereutectic Fe-Cr-C coatings under hard abrasive wear conditions,the hypereutectic Fe-Cr-Ni-C wear resistant coatings were prepared on Q235 steel plate by plasma cladding technology.The nickel content and carbon content were optimized.The effects of vanadium and niobium on hypereutectic Fe-Cr-Ni-C coatings were studied.The microstructure and properties of the coatings were characterized by metallographic microscope,scanning electron microscopy,energy spectrum analyzer,hardness tester and abrasive wear tester.The surface of plasma cladding hypereutectic Fe-Cr-Ni-C coatings was well formed and the dilution rate of the coatings was controlled at about 21%.By increasing the nickel content of the coatings,the crack sensitivity of the coatings was effectively reduced.However,the wear resistance of the coatings significantly reduced when the nickel content was too high.It could enhance the wear resistance of the coatings when the carbon content of the coatings increased in a certain range,but the crack sensitivity increased and the wear resistance reduced when the carbon content of the coatings was too high.The wear resistance of the hypereutectic Fe-Cr-Ni-C coatings under brown corundum abrasive wear condition was significantly lower than that of quartz sand abrasive.In order to improve the wear resistance of the coatings under brown corundum abrasive wear conditions,the vanadium with mass fractions of 2%,4%,6%and 8%was added to the hypereutectic Fe-Cr-Ni-C deposited alloy powder,respectively.The results showed that vanadium was mainly distributed in M7C3 carbide and the vanadium content in austenite was lower.The microhardness of primary M7C3 carbide increased first and then decreased with the increase of vanadium content.The microhardness of primary M7C3 carbide was the highest when the vanadium content was 6%.The relative wear resistance of the coatings increased from 3.23 to 5.35 when the vanadium content increased from 2%to 6%.By adding vanadium into hypereutectic Fe-Cr-Ni-C deposited alloy powder,the hardness and toughness of primary M7C3 carbide was increased.Therefore,the cutting wear effect of abrasive on primary carbide was effectively reduced and the wear resistance of the coatings under hard abrasive wear conditions was enhanced.In order to further improve the wear resistance of the coatings under brown corundum abrasive wear conditions,the niobium with mass fractions of 1%,2%,3%and 4%was added into the hypereutectic Fe-Cr-Ni-C deposited alloy powder with 6%vanadium content.The results showed that the irregular primary MC-type composite carbides could be formed in the hypereutectic Fe-Cr-Ni-C deposited alloy powder by adding niobium and vanadium.The niobium element was mainly distributed in the primary MC carbides.The size of primary MC carbides increased gradually with the increase of the niobium content.When the content of niobium increased from 1%to 4%,the relative wear resistance of the coatings increased from 5.35 to 11.97,but the increasing range tended to be gentle.By adding niobium and vanadium into hypereutectic Fe-Cr-Ni-C coatings,the microhardness of primary M7C3 carbide and eutectic(?+M7C3)structure could be effectively increased,the cutting wear effect of abrasive on primary carbide and eutectic structure was effectively reduced,the wear resistance of the coatings under hard abrasive wear conditions was significantly enhanced.The wear resistance of the composite coatings strengthened by niobium and vanadium was significantly better than that by single element niobium and vanadium.