激光熔丝定向能量沉积IN718合金的显微组织与力学性能

Microstructure and mechanical properties of IN718 alloy by wire-laser directed energy deposition

摘要

IN718合金构件在航空航天耐高温零部件中应用广泛，但传统机加工制备流程长，材料利用率低。选用激光熔丝定向能量沉积工艺制备IN718合金，分别采用X射线衍射、扫描电镜、能量散射光谱、电子背散射衍射表征合金的物相组成、微观形貌、析出相种类和晶粒特征，利用万能拉伸试验机和显微硬度计表征合金力学性能。结果表明，IN718合金组织基体为γ相，晶界或亚晶界处存在Laves析出相。不同表面组织和性能差别较大，XOY面主要为等轴晶，平均晶粒尺寸最小，XOZ面和YOZ面由等轴晶和粗大柱状晶组成，YOZ面平均晶粒尺寸最大。沿Y方向抗拉强度最高，为842.5 MPa，对应的断后伸长率为17.5%；沿X方向断后伸长率最高，为29.5%，相应的抗拉强度为818.7 MPa。XOY面、XOZ面和YOZ面硬度分别为314HV_0.2、267HV_0.2和229HV_0.2。

Abstract

IN718 alloy components are widely employed in high-temperature parts for aerospace applications. However，traditional machining methods are not only time-consuming but also lead to inefficient material utilization. This study introduces the fabrication of IN718 alloy through wire-laser directed energy deposition (W-LDED) technique. The alloy’s phase composition，microstructure，types of precipitated phases，and grain characteristics are characterized using X-ray diffraction，scanning electron microscopy，energy-dispersive spectroscopy，and electron backscatter diffraction. The mechanical properties of the alloy are evaluated using a universal tensile testing machine and a microhardness tester. The matrix of the IN718 alloy consists of the γ phase，with Laves precipitate phase located at the grain boundaries or sub-grain boundaries. Notable differences in surface microstructures and properties are observed across various planes. The XOY surface predominantly exhibits equiaxed grains with the smallest average grain size，whereas the XOZ and YOZ surfaces comprise a mix of equiaxed grains and coarse columnar grains，with the YOZ surface displaying the largest average grain size. The highest tensile strength，reaching 842.5 MPa，is recorded along the Y direction，accompanied by an elongation of 17.5%. Conversely，the highest elongation，at 29.5%，is noted in the X direction，with a tensile strength of 818.7 MPa. The hardness values of the XOY，XOZ，and YOZ surfaces are 314HV_0.2，267HV_0.2，and 229HV_0.2，respectively.

关键词

激光熔丝定向能量沉积 / IN718合金 / 各向异性 / 显微组织 / 力学性能

Key words

wire-laser directed energy deposition (W-LDED) / IN718 alloy / anisotropy / microstructure / mechanical property

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基金资助

国家重点研发计划资助项目(2024YFB4609702)