K42O2高温合金激光选区熔化成形微观组织研究

为了实现激光选区熔化成形(SLM)这项新工艺在液体火箭发动机高温合金结构上的推广应用,明晰其强化机理以及研究相应的热处理制度,对激光选区熔化快速凝固条件下组织形成及演化规律、第二相析出特点进行了分析和讨论.采用SLM成形K4202镍基高温合金试样,通过光学显微镜(OM)、扫描电镜(SEM)及X射线衍射(XRD)等理化分析手段,将基于ANSYS生死单元技术的温度场数值模拟结果和经典凝固理论相结合,揭示了其组织特征及演化规律:沉积态表现为外延生长柱状晶,层间可见层带组织,顶部出现转向枝晶和二次枝晶臂,γ'强化相和碳化物的析出受到抑制.

Microstructure of selective laser melted nickel-based superalloy K42O2

In order to realize the popularization and application of selective laser melting (SLM) innovative process in the liquid rocket superalloy structure,its strengthen mechanism and corresponding heat treatment regime are revealed.The microstructure formation,evolution laws and phase formation characteristics of SLM under rapid solidification condition are discussed and analyzed in this article.The optical micrograph (OM),scanning electron microscopy (SEM),X-ray diffraction (XRD),and ANSYS thermal simulation combining with classic solidification theory were adopted on a K4202 superalloy sample fabricated by SLM to reveal its microstructure characteristics and evolution laws.It was observed that the as-deposited microstructure was out-of-equilibrium,composed of epitaxial elongated columnar crystal paralleling to the deposition direction,but at the top of the SLM sample the dendrites grew along the laser scanning direction and appeared as secondary dendrite arm,and the precipitated phases were inhibited.