电子束重熔对熔丝沉积钛合金表面组织及性能的影响  

Effect of Electron Beam Surface Remelting on Surface Microstructure and Properties of Wire-feed Additive Manufactured Titanium Alloy

作　　者：迮颖 朱梦婷 孙世豪 陶学伟[1,2] 张保森 姚正军[3] ZE Ying;ZHU Meng-ting;SUN Shi-hao;TAO Xue-wei;ZHANG Bao-sen;YAO Zheng-jun(School of Materials Science and Engineering,Nanjing Institute of Technology,Nanjing 211167,China;Jiangsu Key Laboratory of Advanced Structural Materials and Application Technology,Nanjing 211167,China;School of Materials Science and Technology,Nanjing University of Aeronautics and Astronautics,Nanjing 210016,China;JITRI Institute of Precision Manufacturing,Nanjing 211800,China)

机构地区：[1]南京工程学院材料科学与工程学院,南京211167 [2]江苏省先进结构材料与应用技术重点实验室,南京211167 [3]南京航空航天大学材料科学与技术学院,南京210016 [4]江苏集萃精密制造研究院有限公司,南京211800

出　　处：《表面技术》2023年第4期164-171,共8页Surface Technology

基　　金：国家自然科学基金(52005245);江苏省大学生科技创新项目(202011276069Y)。

摘　　要：目的通过表面重熔处理解决沉积钛合金固有组织引起的表面磨损不均及摩擦不稳定的难题,以拓宽沉积钛合金的应用领域。方法采用电子束重熔工艺对熔丝沉积Ti6Al4V钛合金表面进行改性处理。利用体式显微镜、光学显微镜、X射线衍射仪等分析重熔前后钛合金表层的宏观形貌、显微组织及物相组成变化,运用纳米压痕仪及摩擦磨损试验机考察重熔层的表面纳米力学性能及耐磨性能,并采用三维光学轮廓仪及扫描电子显微镜观察磨损形貌特征。结果经电子束重熔处理后,熔丝沉积钛合金沉积方向表面组织由不均匀的α+β组成的网篮组织及魏氏组织转变为均匀分布的细针状马氏体(α’)。重熔处理试样表面纳米硬度均匀,且得到明显提升,达3.8 GPa,相较于未重熔试样提高了15%以上,表现出较高的硬弹性。重熔层具有稳定的摩擦系数和较优的耐磨性,其平均摩擦系数为0.45,磨损率为3.59×10^(-13)mm^(3)/(N·m),相较于未重熔试样,分别降低了19.6%和22.1%,其磨损机理以磨粒磨损、氧化磨损及粘着磨损为主。结论电子束重熔工艺能够有效改善熔丝沉积钛合金沉积方向的表面组织均匀性,可获得优异的表面力学性能及摩擦性能。Electron beam surface remelting is an advanced high-energy beam surface-modification technology that allows to locally manipulate the microstructure and performance without affecting the matrix material.It has attracted much attention for the fabrication of active and refractory materials,since a vacuum working environment can effectively avoid the introduction of extrinsic contaminants.The work aims to address the problems of insufficient wear resistance and friction instability resulted from the inherent microstructure of wire-feed additive manufactured titanium alloy through electron beam surface remelting to,broaden its application fields.The square specimens(15 mm×15 mm×4 mm)were extracted from the electron beam free form fabricated Ti6Al4V alloy along the build direction.The polished specimens were treated by surface melting technique with an electron beam gun under a vacuum of 10–3 Pa,with fixed beam power of 180 W and moving speed of 5 mm/s.The overlap ratio between the two adjacent passes was 50%.The variation of macroscopic morphology,microstructure and phase composition of the titanium alloy before and after remelting were analyzed with stereomicroscope,optical microscope and X-ray diffractometer,respectively.The surface nanomechanical properties and wear resistance of the remelted layer were investigated with nanoindenter and wear testing machine,respectively.The worn features were characterized with three-dimensional optical profilometer and scanning electron microscope.A favorable remelted layer was successfully prepared on the surface of deposited titanium alloy via electron beam surface remelting.Under the irradiation of electron beam,the as-received surface was melted completely into a molten pool,and then was rapidly solidified afterwards by self-quenching.Therefore,the initial heterogeneous microstructure(basket-wave structure and Widmanstatten structure composed ofα+β)was transformed into homogeneous and fine acicular martensite(α′)after surface remelting treatment.The nanoindentation

关 键 词：电子束重熔 熔丝沉积 钛合金 组织均匀性 耐磨性 

分 类 号：TH117[机械工程—机械设计及理论]