Effects Of Y And Ce Elements On Microstructure And Properties Of Fe-Cr-C-B Hardfacing Layer

Fe-Cr-C surfacing alloy has been applied to various industrial fields because of its excellent wear resistance.In the era of rapid development of manufacturing industry,the wear resistance of materials is becoming more and more strict.Therefore,it is imperative to develop new wear-resistant materials.In this paper,low-cost carbon steel is used as base metal,B,Y and Ce elements are added into Fe-Cr-C alloy system to prepare flux cored wire,and wear-resistant hardfacing alloy is prepared by GMAW.Firstly,the effect of welding process on the formation of surfacing layer was studied,and the phase composition and microstructure of surfacing layer were analyzed.The relationship between microstructure and wear resistance of surfacing layer was studied,and then the wear resistance mechanism of surfacing layer was discussed.The conclusions are as follows:(1)Appropriate welding process can ensure good weld formation,no porosity,cracks and other defects.For fe-cr-c-b hardfacing alloy,its microstructure is mainly composed of austenite(?-Fe),ferrite(?-Fe),M₇(C,B)₃ and M₂B phases.The microstructure of surfacing layer presents dendrite structure,which is composed of eutectic structure of austenite and carbon boron compound.The physical property of B is similar to that of C,which can promote the precipitation of carbides and solid solution into carbides,so as to improve the wear resistance of surfacing layer.With the increase of B content,the primary austenite phase decreases and the eutectic structure increases.When B content is 3%,the refining effect is the most obvious,and the wear loss reaches the minimum and the wear resistance is the best.(2)For Fe-Cr-C-B-Y surfacing alloy,the phase type of the surfacing layer with nano Y₂O₃ has not changed,and the microstructure is still composed of austenite(?-Fe),ferrite(?-Fe),M₇(C,B)₃ and M₂B phases.With the increase of Y content,the shape,structure,size and quantity of carboboride in the surfacing layer change,and the carboboride changes from strip to hexagonal structure.The refinement effect of carboboride on the microstructure is significantly improved.The hardness first increases and then decreases,and the wear amount first decreases and then increases.When the Y content is 1.6%,the matrix phase matches the eutectic structure best,and the wear resistance is the best.Compared with Fe-Cr-C-B surfacing alloy,the microstructure is finer and the wear resistance is better.(3)For Fe-Cr-C-B-Ce hardfacing alloy,the phase type of the hardfacing layer with Nano-Ce O2 does not change,and the microstructure is still composed of austenite(?-Fe),ferrite(?-Fe),M₇(C,B)₃ and M₂B phases.After adding Ce,the rare earth elements can deoxidize and desulfurize the surfacing layer,reduce the inclusions in the surfacing layer,change the existing form of inclusions,and play the role of purification and modification.With the increase of Ce content,the carbides in the surfacing layer gradually change from strip structure to hexagonal structure,and the refinement effect on the structure is significantly improved.When the Ce content is 1.6%,the wear resistance is the best.With the increase of Ce content,the carboboride in the surfacing layer is spheroidized and the wear resistance decreases.Compared with Fe-Cr-C-B hardfacing alloy,the addition of Ce hinders the grain boundary migration,reduces the grain size,improves the hardness and enhances the wear resistance.(4)For Fe-Cr-C hardfacing alloy,carbide hard phase with higher hardness is formed,and carbon boride hard phase with higher hardness is formed by adding B to replace part of C in the matrix,which plays the role of second phase strengthening;by adding nano Y₂O₃and Ce O₂,dislocation movement is hindered,strength is improved,grain boundary migration is hindered,grain size is reduced,hardness and plasticity are improved at the same time,which plays an important role It can improve the structure of precipitated hard phase and play the role of fine grain strengthening.