Theoretical Calculation And Experimental Research Of Refinement On MC Carbides By CeO₂ In Hypereutectic Fe-Cr-C Hardfacing Alloy

The lattice misfit of the different CeAlO₃/NbC,CeO₂/TiC and CeO₂/TiC planes were calculated by Bramfitt two-dimensional lattice misfit degree theory.Then,the interface relation of CeO₂?100?/NbC?111?,CeAlO₃?110?/NbC?111?and CeO₂?100?/TiC?111?were calculated by first-principles.The possibilities of CeO₂ and CeAlO₃ as the heterogeneous nucleus of MC?TiC?NbC?were analyzed as well.Hypereutectic Fe-Cr-C-Nb,Fe-Cr-C-Nb-CeO₂,Fe-Cr-C-Ti and Fe-Cr-C-Ti-CeO₂ hardfacing alloy were prepared by flux-cored wire hardfacing in this paper.Its microstructure and wear microstructure were observed by X-Ray Diffractometer,Scanning Electron Microscope?SEM?,Transmission Electron Microscope?TEM?,Optical Microscope?OM?and CSM friction-abrasion testing,and the wear resistance was studied.The calculated results show that the lattice misfit of CeO₂?100?/NbC?111?,CeAlO₃?110?/NbC?111?and CeO₂?100?/TiC?111?are 7.85%,7.2%and 6.09%respectively,which indicates that they are moderately effective for the CeO₂ and CeAlO₃ as the TiC and NbC heterogeneous nucleus.There are four interfaces between CeO₂ and NbC,which are Ce-C,Ce-Nb,O-C?O-Nb ones.The interface adhesive works of O-Nb are smallest and its interface energies is largest,whose O-Nb interface is thermodynamic stable.Moreover,O-Nb interface consists of covalent,ionic and metallic bonds.There are 6interfaces between CeAlO₃ and NbC,where interface-3 structure is the most stable.Interface-3 consists of a large number of ionic bonds.There are four interfaces exist between CeO₂ and TiC,which are Ce-C,Ce-Ti,O-C,and O-Ti ones.The interface energies of O-Ti interfaces are smallest,which indicates that the two interfaces are thermodynamic stable.In addition,The O-C interface consists of covalent and metallic bonds,meanwhile the O-Ti interface consists of covalent,ionic and metallic bonds.Therefore,CeO₂ and CeAlO₃ can be as the heterogeneous nucleus of MC.The experimental results show that CeO₂ exists in MC,which proves that CeO₂ can be as the heterogeneous nucleus of MC,then refines MC.The wear rate of the Fe-Cr-C-M hardfacing alloy with CeO₂ is decreased,which indicates its wear resistance is increased.