激光选区熔化DD91镍基单晶高温合金的单道形貌、晶体取向和微观组织  

Crystal Orientation and Microstructure of DD91 Nickel-Based Single Crystal Superalloy Fabricated by Selective Laser Melting

作　　者：李继康 张振武 杨源祺 蔡超[1] 李伟 魏青松[1] Li Jikang;Zhang Zhenwu;Yang Yuanqi;Cai Chao;Li Wei;Wei Qingsong(State Key Laboratory of Material Processing and Die&Mould Technology School of Materials Science and Engineering,Huazhong University of Science and Technology,Wuhan 430074,Hubei,China;Key Laboratory of Metallurgical Equipment and Control Technology Ministry of Education,Wuhan University of Science and Technology,Wuhan 430081,Hubei,China;Hubei Key Laboratory of Mechanical Transmission and Manufacturing Engineering,Wuhan University of Science and Technology,Wuhan 430081,Hubei,China;Precision Manufacturing Institute,Wuhan University of Science and Technology,Wuhan 430081,Hubei,China)

机构地区：[1]华中科技大学材料科学与工程学院材料成形与模具技术国家重点试验室,湖北武汉430074 [2]武汉科技大学冶金装备及其控制教育部重点实验室,湖北武汉430081 [3]武汉科技大学机械传动与制造工程湖北省重点实验室,湖北武汉430081 [4]武汉科技大学精密制造研究院,湖北武汉430081

出　　处：《中国激光》2022年第14期29-39,共11页Chinese Journal of Lasers

基　　金：国家自然科学基金(51905193,51775207);湖北省重点研发计划项目(2020BAB049);华中科技大学学术前沿青年团队项目(2017QYTD06);中央高校基本科研业务费专项资金(2021yjsCXCY028)。

摘　　要：采用激光选区熔化成形了DD91镍基单晶高温合金的单条熔道,研究了激光功率和扫描速度对单道形貌、晶体取向和微观组织的影响规律。结果表明:当铺粉层厚为30μm时,在激光功率290~305 W、扫描速度500~700 mm/s工艺窗口内,熔道连续平稳且光滑平直,熔池扁平规则,可为单晶组织的稳定生长提供保障。当熔池与单晶基板冶金良好时,熔池内晶体能够延续基板的取向沿[001]定向外延生长,但熔池对流可使晶体生长方向产生2°以内的小角度偏差,并在熔池顶部发生柱状晶向等轴晶的转变,产生杂晶缺陷。熔池底部、两侧和中部都存在大量沿[001]生长的柱状枝晶,一次枝晶臂间距为0.6~0.8μm,实现了沿单晶基板的外延生长,但中部晶体形态转变为纺锤状;熔池顶部晶粒为细小胞状结构,生长方向由[001]转变为[100],这主要是顶部凝固时热量更多地沿扫描方向(平行于基板)传递导致的。研究结果可为激光增材制备大尺寸单晶组织提供参考。Objective Nickel-based single crystal superalloys have excellent high-temperature properties and are mainly used in the manufacture of aero-engine turbine blades.A high temperature gradient is the key to single crystal formation.Selective laser melting(SLM)is a kind of metal additive manufacturing,which uses a laser as the heat source to form the parts with fine metal powders layer by layer,especially the complex structures.The small laser spot(80--100μm)has extremely high thermal density,which promotes a temperature gradient of 10^(3)--10^(5) K/cm and a solidification rate of 10^(5)--10^(7) K/s in the molten pool.In addition,a laser has obvious directional heat transfer characteristics,and the solidification heat can be directionally dissipated along the path from the molten pool to the substrate.Therefore,to explore the feasibility of single crystals fabricated by SLM,thirty-five single track samples are fabricated under different laser powers and scanning speeds.The geometric features,crystal orientation,and microstructures are first analyzed systematically.Then,the formation mechanisms of cracks and stray grains are discussed,which provides theoretical and technical reference for the preparation of large-scale single crystal structures by SLM.Methods The particle size distribution of the gas-atomized DD91 nickel-based single crystal superalloy powder is in the range of 8.6--37.5μm with an average of 20.4μm.The SRR99 single crystal substrate prepared by directional solidification is tested by electron backscattered diffraction(EBSD)and it is found that the grain grows along the direction of[001],which meets the experimental needs.Before the experiment,the powder is placed in an oven at 80℃for 10 h to remove moisture.The single crystal substrate is polished with sandpaper,and impurities such as abrasive debris are removed in an ultrasonic cleaning machine.DD91 alloy powder with a layer thickness of 30μm is spread on the(001)crystal surface of the SRR99 single crystal substrate.A self-developed SLM equipme

关 键 词：激光技术 激光选区熔化 DD91合金 镍基单晶高温合金 单道 晶体取向 微观组织 

分 类 号：TG146.1[一般工业技术—材料科学与工程]