电磁辅助激光成形修复GH4169合金Laves相分析

Laves Phase Precipitation of Laser Repaired GH4169 Superalloy Assisted by Electromagnetic Stirring

利用电磁搅拌辅助激光成形修复技术修复了带有V形槽缺陷的GH4169高温合金,通过改变磁场电流强度比较了修复区Laves相形貌与体积分数,并测量了枝晶间、枝晶干Nb元素含量,研究了磁场电流大小与元素偏析和材料硬度之间的关系。结果表明:电磁搅拌作用下Laves相的形貌发生了明显改变,由连续网状分布逐渐变为短蠕虫状和颗粒状,Laves相的体积分数有所减小;枝晶干γ基体Nb元素的含量随着搅拌磁场的增大而增加,当磁场电流为60 A时,Nb元素的平均含量达到3.72%(质量分数),较未施加电磁搅拌的试样增加了0.33%。硬度测试显示,电磁搅拌作用显著提高了修复试样的显微硬度,这与Nb等合金元素在枝晶干基体γ相中固溶度的提高有关。分析认为,电磁搅拌促进了垂直于枝晶生长方向熔池液态金属的流动,促进了溶质元素的均匀分布,使枝晶臂的生长更发达,共晶组织分布更均匀。

GH4169 alloy samples with V-grooves were experimentally repaired by electromagnetic stirring assisted laser repairing under different magnetic field currents.The morphologies and volume fraction of Laves in the repaired zone were compared,and the contents of Nb element in the matrixγand the hardness of the repaired sample were measured by changing the magnetic field currents to explain the relationship between the magnetic field currents and the element segregation as well as mechanical properties.The results show that with the assistance of electromagnetic field,the morphology of Laves is obviously changed from reticulate to rod-like and granular shape and its volume fraction is decreased.The content of Nb element in the matrixγis increased with the increase of the magnetic field current.When the magnetic stirring current is 60 A,the content of Nb element is 3.72 wt%,and it is increased by 0.33% compared to that without electromagnetic stirring.The hardness test shows that the electromagnetic stirring greatly increases the hardness of the repaired sample,which is related to the increase in the solid solubility of alloy elements such as Nb in theγphase of dendrite core.The electromagnetic stirring improves both the flow of liquid metal in the melting pool vertical to the dendrite growth direction and the homogeneous distribution of solute element;as a result,the dendrite arm is more developed and the eutectic structure is more homogeneous.