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研究了激光成形修复航空发动机涡轮叶片用K418高温合金的组织特征与开裂行为。研究发现:K418合金激光修复区组织主要由γ-FeCr0.29Ni0.16C0.06固溶体基体、方形γ′相、枝晶间杆状或骨架状初生MC碳化物和骨架状(γ+MC)共晶组成。激光成形修复所用铸件基体中MC碳化物为TiC,呈块状分布在晶内和晶界;而激光修复区中MC碳化物为(NbTi)C,呈骨架状或杆状分布于枝晶间。从基体、热影响区到修复区,γ′相形貌、尺寸和数量呈现不同特征。修复区裂纹为与液膜有关的结晶裂纹,裂纹沿枝晶晶界扩展。通过试验优化,确定了较佳的激光成形修复K418合金的工艺参数,大大降低了其开裂倾向。
The microstructure and cracking behavior of K418 superalloy used in laser engine for aeroengine turbine blade were studied. The results show that the microstructure of K418 alloy is mainly composed of γ-FeCr0.29Ni0.16C0.06 solid solution matrix, square γ ’phase, dendritic rod-like or framework-like primary MC carbide and matrix (γ + MC) eutectic composition. The MC carbides in the matrix of the casting used for laser forming repair are TiC, which are agglomerate distributed in the intragranular and the grain boundaries. The MC carbides in the laser repaired zone are (NbTi) C, which are skeletonized or rod-shaped distributed in the dendrite. From the matrix, the heat affected zone to the repair area, the γ ’phase morphology, size and number show different characteristics. The repaired zone crack is a crystal crack associated with the liquid film and the crack propagates along the dendritic grain boundary. Through experiment and optimization, the process parameters of K418 alloy by laser forming were determined, which greatly reduced the tendency of cracking.