Refinement Of La₂O₃ On Microstructure Of Hypereutectic Fe-Cr-C-?Ti?Hardfacing Alloy

In modern industrial production,many important parts and components of machinery need to operate under high temperature,radiation,oxidation,corrosion and other environments for a long time,which makes them more vulnerable to damage and scrap.The remanufacturing of these important parts by surfacing repair can not only save the replacement cost of parts and reduce the waste of resources,but also extend the service life of the parts and increase the efficiency of enterprises.Surfacing welding technology is an important technical means in surface engineering.Therefore,because of its high hardness,good wear resistance and low price,the hypereutectic Fe-Cr-C hardfacing alloy are favored among surfacing materials.In this paper,the primary M₇C₃ carbides in the hardfacing alloy microstructure being refined by La₂O₃ was theoretically predicted by first principles calculation.The results show that the chemical bond in La₂O₃ phase structure is a combination of ionic bond and covalent bond,there are ionic,metal and covalent bonds among the atoms of M₇C₃ carbide.The La₂O₃?111?/M₇C₃?0001?interfaces can form bonds stably with good interfacial bonding.The hypereutectic Fe-Cr-C hardfacing alloys with and without nano rare earth oxide La₂O₃ were prepared by surfacing.Using fluorescence spectrometer and carbon-sulfur analyzer,the contents of the elements in two kinds of surfacing welding alloys were determined.The los type hardness tester was adopted to measure the hardness,and the CSM ball-disc friction and wear testing machine were used for the wear-resisting performance of the sample.By the microstructure observation,the primary M₇C₃ carbides in the hypereutectic Fe-Cr-C hardfacing alloy were refined with La₂O₃ addition,and the hardness and wear resistance of the surfacing alloy were improved to a certain extent.The phenomenon of M₇C₃ growing around La₂O₃ can be found in SEM and TEM observation and characterization.It can be proved that the La₂O₃ refinement of primary M₇C₃ carbide is the reason for the improvement of surfacing alloy performance.The first principle calculation was used to predict the heterogeneity nucleation relationship between La₂O₃ and TiC.It is found that La₂O₃?110?/TiC?110?interfaces have good interface binding and can also form bonds stably.It provides a theoretical basis for La₂O₃ refining Fe-Cr-C-Ti series surfacing alloys.