预制坡口角度对激光增材再制造IN718合金组织与性能的影响

目的研究在激光增材再制造IN718合金过程中,不同预制坡口角度对其组织与性能的影响。方法利用激光增材再制造技术对不同预制凹槽进行逐层叠加修复,采用光学显微镜观察显微组织,采用扫描电镜观察断口形貌,采用维氏硬度计对再制造试样进行硬度测量,采用残余应力测试仪测量再制造后基体表面的残余应力,采用万能拉伸试验机进行拉伸力学性能测试。结果当预制坡口角度大于130°时,能得到无组织缺陷、成形质量良好的增材再制造试样;当预制坡口角度小于110°时,修复界面会出现熔合不良现象,且修复区内部会出现裂纹。预制大的坡口角度进行激光增材再制造试验能获得组织更加细密、硬度分布更为均匀的再制造层,且大的坡口角度能有效降低再制造试样基体的残余应力。增大坡口角度有助于提高再制造试样的塑性,随着坡口角度的减小,再制造试样的力学性能变差。结论在进行激光增材再制造试验时,不宜预制过小的坡口角度,应根据损伤情况预制坡口角度较大的凹槽,有助于增加再制造成形件的组织均匀性,提高其力学性能。

Influence of Pre-fabricated Groove Angle on Microstructure and Properties of Laser Additive Remanufactured IN718 Alloy

The work aims to investigate the influence of different pre-fabricated groove angles on the microstructure and properties of laser additive remanufactured IN718 alloy. The pre-fabricated grooves were repaired layer by layer by laser additive remanufacturing technology. The microstructure and fracture morphology of the remanufactured samples were observed by optical microscope and scanning electron microscopy, respectively. The hardness, residual stress and tensile mechanical properties of the remanufactured samples were measured by Vickers hardness tester, residual stress tester and universal tensile tester, respectively. When the pre-fabricated groove angle was greater than 130°, the additive remanufactured samples without structural defects and good forming quality could be obtained. When the pre-fabricated groove angle was lower than 110°, the fusion interface might be poorly fused, and cracking might occur on the repaired area. The pre-fabricated larger groove angle could obtain remanufactured samples with finer structure and more uniform hardness distribution during laser additive remanufacturing experiment, and the larger groove angle could reduce the residual stress of the remanufactured sample matrix. Increasing the groove angle could significantly improve the plasticity of the remanufactured samples. As the groove angle decreased, the mechanical properties of the remanufactured samples deteriorated. During the laser additive remanufacturing process, it is not suitable to pre-fabricate too small groove angle, the groove with larger groove angle should be pre-fabricated according to the damage condition, which is beneficial to improving the uniformity and mechanical properties of the remanufactured sample.