激光立体成形K465高温合金的组织研究

Study on Microstructure of Laser Solid Forming K465 Superalloy

摘要:

采用激光立体成形技术制备了K465镍基高温合金试样，研究了晶粒、γ′强化相及碳化物等组织的特征及演化规律。结果表明：试样中心区域内晶粒粗大，顶部边缘区域晶粒细小；试样内枝晶呈现明显的沿沉积方向外延生长特点，在接近试样底部的部分熔覆层顶部由于重熔不完全而出现转向枝晶区；熔覆层交界处的γ′相尺寸略大于层内的γ′相，枝晶间的γ′相尺寸略大于枝晶干上的γ′相；MC碳化物呈现多种形貌，底部存在分叉发达的花瓣状MC碳化物，中部有较多短棒状MC碳化物，顶部存在棒状和八面体状的MC碳化物。

Abstract:

A sample of K465 nickel-base superalloy was prepared by laser solid forming (LSF) technology. The microstructure evolution of grains, γ′ phase and carbides was investigated. It is found that the central region of the sample consists of coarse grains, while the top edge of the sample consists of fine grains. Dendrites in the sample present apparent epitaxial growth along the deposition direction, but the vergens dendrites appear occasionally at the top of several cladding layers near the bottom of the sample due to the inadequate remelting depth. The γ′ particles at the junction of adjacent cladding layers are larger than that inside the layers, and the interdendritic γ′ phase is larger than that at the core of dendrites. MC carbides present variable morphology in the sample, that is, flowerlike at the bottom, short rod-like in the middle and octahedral at the top.