Microstructure And Properties Of Middle And High Carbon Steel Hardfacing Alloy With Y₂O₃as Well As Numerical Simulation

Because of the high hardness and wear resistance, the workpieces manufactured bymedium and high carbon steels, such as hot forging die and hot roller, are widely appliedin metallurgical and mechanical industries. After being in service for a period of time,these workpieces failed because of the thermal fatigue and excessive wear. The shape andsize of the failed workpieces can be restored by means of hard-face-welding (hardfacing),which is one of the best effective methods of remanufactured technologies. With the rareearth elements is more and more widely used, it is necessary to develop good weldability,high wear resistance, thermal fatigue resistance of the flux-cored wire.In this paper, the medium and high carbon steels were taken. Flux-cored wires withdifferent Y2O3additives were developed. The microstructures of the hardfacing coatingwere observed, and wear resistance and thermal fatigue of the hardfacing coating weremeasured, respectively. The wear resistance and thermal fatigue of the hardfacing coatingwere simulated by finite element too.The hardfacing coating with appropriate content of Y2O3can get small homogeneousacicular martensite and reticular high alloy martensite structure, the original austenitegrain size can be effectively refined by Y2O3additives, When Y2O3additive is0.76wt.%,the grain size of the hardfacing coating is the smallest. The refinement mechanism of thehardfacing coating was analyzed by the thermodynamic calculation, and two-dimensionallattice mismatch degree between the rare earth inclusions and primary gamma phase wascaculated. The results indicate that the two-dimensional lattice mismatch degree of YAlO3and primary gamma phase is medium effective; YAlO3can be as heterogeneous nucleationcore of the primary gamma phas, and refined the original austenite grain size effectively.Y2O3can improve the mechanical properties of the hardfacing coating, with theincrease of Y2O3additive, the hardness, the tensile and yield strength, abrasion resistanceand thermal fatigue property of the hardfacing coating can be improved significantly.Friction and thermal fatigue models were established using ANSYS finite elementsimulation software. The temperature field and stress field of the hardfacing coatingspecimens were caculated. The friction and thermal fatigue failure reason is analyzed, andthe fatigue life was predicted.