基于μCT表征的SLM成形GH3536高温合金缺陷特征

Defect characteristics within SLM-fabricated GH3536 superalloy dependence onμCT characterization

选择激光选区熔化(selective laser melting,SLM)工艺中不同激光功率和扫描速度的参数组合制备GH3536高温合金试样,采用μCT技术表征试样内部的孔隙率及缺陷特征,同时采用光学显微镜和扫描电镜验证缺陷类型,并分析熔池形貌。结果表明:SLM工艺参数与合金中缺陷特征和熔池形貌密切相关,优化参数组合时连续性熔池具有较大的长宽比、彼此搭接良好,同时成形试样的孔隙率远低于0.01%,存在随机分布、尺寸较小的气孔;偏离优化参数组合时不仅在间断性熔池界面形成了尺寸较大的孔洞,而且增加了SLM成形过程的不稳定性,形成了少量的未熔合,这两类缺陷均具有一定的各向异性;试样中还存在未能被μCT发现的微气孔和微裂纹。

GH3536 superalloy samples were made by selective laser melting(SLM)with a parameter combination of laser power and scanning speed.The porosity and defect characteristics within the samples were characterized byμCT technique,and the defect types as well as the morphologies of molten pool were analyzed using optical microscope and scanning electron microscope.The results show that process parameters are closely related with defect characteristics and the morphologies of molten pool.As the laser power and scanning speed are optimized,continuous molten pool with a higher aspect ratio overlaps well with each other.The porosity in the fabricated samples is far less than 0.01%,and with randomly distributed small pores.When the deviation from the optimized process parameters occurs,not only larger voids are formed at the interface of discontinuous molten pool,but also the process instability are increased,resulting in the formation of minor amounts of lamellar lack of fusion.The latter two types of defects present a certain anisotropy.Additionally,smaller micropores and microcracks are beyond theμCT detection ability.