搭接工艺对选区激光熔化镍基单晶高温合金DD491晶体取向与微观组织的影响  

Effects of Overlapping Process on Grain Orientation and Microstructure of Nickel-Based Single-Crystal Superalloy DD491 Fabricated by Selective Laser Melting

作　　者：张振武 李继康 许文贺 沈沐宇 戚磊一 郑可盈 李伟[2] 魏青松[1] ZHANG Zhenwu;LI Jikang;XU Wenhe;SHEN Muyu;QI Leiyi;ZHENG Keying;LI Wei;WEI Qingsong(State Key Laboratory of Material Processing and Die&Mould Technology,School of Material Science and Engineering,Huazhong University of Science and Technology,Wuhan 430074,China;Key Laboratory of Metallurgical Equipment and Control Technology,Ministry of Education,School of Mechanical and Automation,Wuhan University of Science and Technology,Wuhan 430081,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全国重点实验室,武汉430074 [2]武汉科技大学机械自动化学院、冶金装备及其控制教育部重点实验室,武汉430081

出　　处：《金属学报》2024年第11期1471-1486,共16页Acta Metallurgica Sinica

基　　金：国家自然科学基金项目No.52275333;中国航空制造技术研究院稳定支持项目No.KZ571801;武汉市知识创新专项项目No.2022010801010302。

摘　　要：镍基单晶高温合金是制造航空发动机单晶涡轮叶片的关键材料,选区激光熔化(SLM)制造单晶组织和复杂结构具有技术优势和可行性。在SLM中,熔道与熔道之间的搭接质量对单晶组织的完整性至关重要。本工作在4种激光功率和扫描速率的组合工艺下,探究了扫描间距(0.06、0.09、0.12和0.15 mm)对第四代镍基单晶高温合金DD491熔道微观形貌、冶金缺陷、晶体取向和微观组织的影响。结果表明,低功率、低速率和高功率、高速率的工艺参数能够为晶体定向生长提供稳定的几何形态和冶金条件,熔道底部晶体能够延续基底取向实现[001]定向生长。熔道内不同区域存在不同类型的晶体取向缺陷,包括顶部中间等轴晶、顶部[010]和[100]柱状杂晶、内部小角度取向偏差等。较小扫描间距的熔道重熔率较高,有利于减少熔道两侧的杂晶缺陷。Aero-engine turbine blades are operated under harsh conditions such as high temperature,pressure,and load.Therefore,weak grain boundaries at high temperatures should be eliminated from the turbine blades,whereas convection channels inside the blades should be added to dissipate heat.Achieving integrated manufacturing of specialized microstructure in complex components has been a long-term research priority in turbine blade manufacturing.Nickel-based single-crystal superalloys are key materials for manufacturing single-crystal turbine blades for aero-engines,and selective laser melting(SLM)is feasible and technically advantageous for manufacturing complex components with single-crystal microstructures.Owing to the extremely high temperature gradient and scanning speed during SLM,the melt pool is unstable,thereby interrupting directional crystal growth.The metallurgical environment of SLM is further complicated by the large number of overlapping tracks and stacking layers.The quality of the overlaps is critical for the integrity of the single-crystal structure during SLM.Herein,the effects of scanning hatch(h=0.06,0.09,0.12,and 0.15 mm)on the melt track morphology,metallurgical defects,crystal orientation,and microstructure of DD491 fourth-generation nickel-based single-crystal superalloy were investigated.Directionally solidified and solution-aged DD6 single-crystal superalloy rods were used as the substrate,and DD491 powder was coated to a thickness of 40μm.Electron backscatter diffraction was used to characterize the crystal orientation of the samples.Results show that low power/low speed(S1)and high power/high speed(S4)combinations of laser power and scanning speed provide geometrically and metallurgically stable conditions for directional crystal growth,and the grains at the bottom of the melt track can orient the substrate to achieve[001]directional growth.Different types of crystal orientation defects were observed in different regions,including equiaxed stray grains in the top middle region,[010]and[100]co

关 键 词：选区激光熔化 镍基单晶高温合金 晶体取向 搭接 

分 类 号：TG146.1[一般工业技术—材料科学与工程]