Study On Microstructure And Property Of Deposited Metal With Fe-Cr-C System

The high carbon and high chromium wear-resisting surfacing-alloys with Fe-Cr-C system equip with high hardness and good combination performance and are widely used in mine,machinery,metallurgy,naval construction and other industries.Self-Shidlded Flux Core Wire(SSFCW)represents the development direction of welding material in the world,four kinds of SSFCW are surfacing on Q235 steel by submered-arc welding,and microstructure and performance of which are analyses by test means of metallographic microscope,Vickers,scanning electronic microscope,energy spectrometer and wear machine.The results of micro-test show that microstructure of deposited metal is mainly composed of carbide,retained austenite and minute quantity martensite.Primary carbide and eutectic carbide are M7C3 type.The width of fusion-line reduce,when the content of carbon increases from 3.8 percent to 6.8 percent,grain of primary carbide become bigger,and growth directivity of which strengthen from slant or non-directional to be perpendicular to wear-resisting surface gradually.Influenced by types and content of alloying element,V is solutioned into matrix and make some primary carbide present square in 1#sample;containning Mo of one percent in 2#sample,primary carbide present irregular hexagon,and the crystal morphology of which present distribution of small clusters;the content of Nb is higher in 3#sample,(Fe,Cr,Nb)7C3 complex carbide form after Fe atom and Cr atom are substitute by Nb element,liquation NbC present quadrangular star and make grains refine and matrix strengthen,and increase stability of retained austenite,primary carbide persent "H"type and uniform distribution;the content of carbon is 6.8 percent,the content of chromium is 29 percent in 4#sample,primary carbide present typical hexagon,and the center shinkage cavity of primary carbide is serious.Hardness test shows that microhardness of deposited metal increases with the increasing of the carbon content,however,the increasing of microhardness is slowly after the content of carbon is up to 5.8 percent.Wear test shows that wear-resisting of deposited metal with Fe-Cr-C system is good,(Fe,Cr)7C3 type carbide is the main wear-resisting phase during wear process,and have effect on antifraying skeleton,can counteract grain-abrasion effectively;perfect matrix(retained austenite and martensite)can resist initiation and expansion of crack and be supply reliable sustain for wear-resisting phase.Relative wear-resisting of deposited metals is 21.2123,27.2012,35.7606 and 19.1968 time to Q235 steel,especially,in 3#sample,because primary carbide present fibre bacillary and uniform distribution in 3#sample,and the combination between NbC and austenite is firm and impervious joint,wear-tesisting property of 3#is optimally.The failure forms of deposited metal are griding abrasion and scaling failure.