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利用自行设计的稳恒磁场装置以辅助激光熔覆工艺,通过调节电流强度获得相应的稳恒磁场作用于激光熔池,在45钢基材表面制备了Fe55合金涂层。借助扫描电子显微镜(SEM)、能谱仪(EDS)和X射线衍射(XRD)等表征手段分析了稳恒磁场作用下Fe55合金涂层的微观形貌、化学组成和物相结构。结果表明,Fe55合金涂层主要由γ-(Fe,Cr)和(Fe,Ni)固溶体、(Cr,Fe)_(23)C_6碳化物及少量Cr9.1Si0.9组成。与未施加磁场相比,稳恒磁场作用下的激光熔覆Fe55涂层,枝晶间Cr元素含量更高,枝晶内Fe元素含量也有所增加。稳恒磁场在一定程度上促进了激光熔池中的传质过程,有助于Fe,Cr元素扩散和(Fe,Cr)固溶体的形成。当电流强度为4.0A时,外加磁场大大降低了熔池内固-液界面前沿的温度梯度,增加了液态金属熔池的形核率,涂层中大量柱状枝晶和树枝晶转变为方向各异的等轴晶,涂层组织得到了明显优化。
The self-designed constant magnetic field device was used to assist the laser cladding process, and the corresponding steady magnetic field was applied to the laser pool by adjusting the current intensity. The Fe55 alloy coating was prepared on the surface of 45 steel substrate. The microstructure, chemical composition and phase structure of Fe55 alloy coating under constant magnetic field were analyzed by scanning electron microscopy (SEM), energy dispersive spectrometer (EDS) and X-ray diffraction (XRD) The results show that the coating of Fe55 alloy consists of γ- (Fe, Cr) and (Fe, Ni) solid solution, (Cr, Fe) _23C_6 carbides and a small amount of Cr9.1Si0.9. Compared with the non-applied magnetic field, the laser-clad Fe55 coating under the action of a steady magnetic field has a higher content of Cr and a higher content of Fe in the dendrite. The steady magnetic field promotes the mass transfer in the laser bath to a certain degree, which is helpful for the diffusion of Fe and Cr and the formation of (Fe, Cr) solid solution. When the current intensity is 4.0A, the applied magnetic field greatly reduces the temperature gradient at the front of the solid-liquid interface in the molten pool and increases the nucleation rate of the liquid metal pool. A large number of columnar dendrites and dendrites change into different directions in the coating Equiaxed grains, the coating organization has been significantly optimized.