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激光同轴熔丝沉积GH4169高温合金微观组织研究

Study on microstructure of GH4169 superalloy fabricated by laser coaxial wire deposition

  • 摘要: 通过激光同轴熔丝增材制造技术,开展了不同偏移量下GH4169高温合金激光熔化沉积试验,系统分析了不同偏移量对沉积层微观组织形貌及显微硬度的影响规律. 结果表明,在不同偏移量条件下,沉积层内部均未观察到气孔缺陷,成形质量良好. 在第2道成形过程中,激光热输入将第1道的沉积层部分熔化,使两道之间实现了良好的冶金结合. 沉积层与基材结合处的熔化区域呈现出典型的“W”形熔合线特征,表明熔池流动与热传导分布均匀. 基材区与增材区之间存在明显的晶粒过渡区域,该区域内晶粒尺寸较为细小,组织结构致密. 增材区内枝晶间析出大量连续分布的长条状析出相,沿枝晶方向定向排列. 显微硬度测试结果显示,第2道的硬度略高于第1道,整体硬度呈现上升趋势,这主要与逐道沉积过程中的热积累效应及析出相的分布特征密切相关.

     

    Abstract: Through the laser coaxial wire additive manufacturing technology, laser melting deposition experiments of GH4169 superalloy under different offsets were carried out, and the effects of different offsets on the microstructure morphology and microhardness of the deposited layers were systematically analyzed. The results indicate that under different offset conditions, no porosity defects are observed inside the deposited layers, and the forming quality is good. During the forming process of the second pass, the laser heat input partially melts the deposited layer of the first pass, achieving good metallurgical bonding between the two passes. The melting region at the bonding interface between the deposited layer and the substrate exhibits a typical “W”-shaped fusion line characteristic, indicating that the molten pool flow and heat conduction distribution are uniform. There is an obvious grain transition zone between the substrate zone and the additive zone, where the grain size is relatively fine, and the microstructure is dense. In the additive zone, a large number of continuously distributed elongated precipitated phases precipitate between the dendrites, which are directionally arranged along the dendrite direction. The microhardness test results show that the hardness of the second pass is slightly higher than that of the first pass, and the overall hardness exhibits an increasing trend, which is mainly closely related to the heat accumulation effect during the pass-by-pass deposition process and the distribution characteristics of the precipitated phases.

     

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