低能量密度对选区激光熔化制备新型镍基高温合金的组织和性能的影响

Microstructure and Mechanical Properties of New Nickel-Based Superalloys Fabricated by Selective Laser Melting at Low Energy Density

摘要:

为了探讨不同能量密度对选区激光熔化（SLM）ZGH401合金的显微组织和力学性能的影响，采用正交试验方法，在不同激光功率和扫描速度下制备了ZGH401合金。采用扫描电镜、电子背散射衍射和电子探针显微分析技术对沉积态ZGH401的微观结构进行了分析。结果表明：随着能量密度的不断增大，沉积态ZGH401的缺陷逐渐减少，相对密度逐渐增大，最终密度可达99.6%。随着激光功率的增加，ZGH401的硬度也随之增加；更快的扫描速度降低了沉积态ZGH401的残余应力。此外，由于垂直沉积方向相比于平行沉积方向晶界更多，因此垂直沉积方向试样的室温拉伸性能更为优异。该合金析出相主要为碳化物和Laves相，熔池边界处的碳化物少于熔池内的碳化物。

Abstract:

ZGH401 alloy was prepared under varying laser power levels and scanning speeds by the orthogonal test method using selective laser melting (SLM). The effect of different energy densities on microstructure and mechanical properties of the formed alloy was investigated. The microstructure of ZGH401 was analyzed by scanning electron microscope, electron back-scattered diffraction, and electron probe microanalysis. The results show that the defects of the as-built ZGH401 are gradually reduced, the relative density is correspondingly enhanced with increasing the energy density, and the ultimate density can reach 99.6%. An increase in laser power leads to a corresponding rise in hardness of ZGH401, while a faster scanning speed reduces the residual stress in as-built ZGH401 samples. In addition, better tensile properties are achieved at room temperature due to more grain boundaries perpendicular to the build direction than parallel to the build direction. The precipitated phases are identified as carbides and Laves phases via chemical composition analysis, with fewer carbides observed at the molten pool boundaries than within the molten pools.