GH4169合金激光沉积修复组织与性能研究

发布时间：2018-04-13 02:28

本文选题：激光沉积修复 + GH4169合金　；参考：《沈阳航空航天大学》2017年硕士论文

【摘要】：GH4169高温合金由于其在高温环境下具有优良的综合使用性能,广泛应用于航空航天、核能、石油化工及其他领域,尤其在航空航天领域存在大量高温合金制造的大型薄壁零件。这些零部件在机械加工过程中不可避免地会产生如尺寸超差、铣切沟槽等误加工损伤,且在服役使用过程中也会产生裂纹、腐蚀和磨损等损伤。本文主要针对表面损伤试样,开展了激光沉积修复工艺研究,重点研究了GH4169合金激光修复、预热下激光修复、热处理等的显微组织特征、拉伸性能、拉伸断口等内容。研究主要成果如下:针对GH4169合金薄壁零部件表面损伤修复研究问题,开展了不同厚度基体的激光沉积修复试验研究,研究并分析了修复件的残余应力、微观组织及室温拉伸性能的变化规律。研究发现,基体厚度越小,残余应力增加,枝晶间析出的Laves相体积分数变大,拉伸性能降低。可见基体厚度对表面损伤修复试样的拉伸性能及显微组织影响显著。针对GH4169合金表面损伤修复试样性能弱化问题,开展了不同基体厚度的预热修复研究,研究了基体预热对残余应力、显微组织及拉伸性能等的影响规律。试验表明:当基体预热至300°C时,其残余应力均明显降低,Laves相变得粗壮并呈现出颗粒状的碎化趋势,抗拉强度略微降低,但断后伸长率提高了60%以上。试验表明基体预热有利于提高激光沉积修复GH4169合金的塑性。针对激光沉积修复GH4169合金过程中存在较大残余应力问题,开展了低能量输入激光沉积修复GH4169合金试验研究。试验表明,采用600w低能量输入进行损伤试样的激光沉积修复,修复试样的残余应力较1400w高能量输入小,可获得较小热影响区。针对激光沉积修复工件的力学性能下降问题,开展了局部热处理和真空热处理的试验研究。研究发现,经热处理后,局部热处理试样修复区平均硬度增加,真空热处理试样修复区平均硬度也增加,略高于局部热处理。两种热处理方式下拉伸断口的韧窝尺寸较沉积态变化不大。试验表明局部热处理和真空热处理都可达到提高拉伸性能的目的。
[Abstract]:GH4169 superalloys are widely used in aerospace, nuclear energy, petrochemical and other fields because of their excellent comprehensive performance in high temperature environment. Especially in aerospace, there are a large number of large thin-walled parts made of superalloys.In the process of machining these parts will inevitably produce damage such as dimension oversize milling grooves and so on. Also cracks corrosion and wear will occur in the course of service and use.In this paper, the laser deposition and repair technology for surface damage samples was studied, and the microstructure, tensile properties and tensile fracture of GH4169 alloy were studied in detail, such as laser repair, laser repair under preheating, heat treatment and so on.The main results are as follows: aiming at the problem of surface damage repair of thin wall parts of GH4169 alloy, the laser deposition repair experiments of different thickness matrix are carried out, and the residual stress of the repair parts is studied and analyzed.Changes of microstructure and tensile properties at room temperature.It is found that the smaller the matrix thickness, the greater the residual stress, the larger the volume fraction of the Laves phase precipitated between dendrites, and the lower the tensile properties.The effect of matrix thickness on the tensile properties and microstructure of surface damage repair specimens is obvious.Aiming at the problem of weakening the properties of GH4169 alloy surface damage repair specimen, the preheating repair of different matrix thickness was carried out, and the influence of matrix preheating on residual stress, microstructure and tensile properties was studied.The experimental results show that the residual stress of Laves phase decreases obviously when the matrix is preheated to 300 掳C, and shows a tendency of granular fragmentation, and the tensile strength decreases slightly, but the elongation increases by more than 60% after breaking.The results show that the preheating of the substrate is beneficial to improve the plasticity of the GH4169 alloy by laser deposition.Aiming at the problem of residual stress in the process of laser deposition and repairing of GH4169 alloy, the experimental study of low energy input laser deposition for repairing GH4169 alloy was carried out.The experimental results show that the residual stress of the damaged specimen is smaller than that of the high energy input of 1400w, and a smaller heat affected zone can be obtained by using 600w low energy input to repair the damaged sample by laser deposition.Aiming at the degradation of mechanical properties of workpiece repaired by laser deposition, the experimental study of local heat treatment and vacuum heat treatment was carried out.It is found that after heat treatment, the average hardness of the repair zone of the local heat treatment specimen increases, and the average hardness of the vacuum heat treatment sample area increases, which is slightly higher than that of the local heat treatment.The dimple size of tensile fracture has little change compared with that of deposition under two kinds of heat treatment.The results show that both local heat treatment and vacuum heat treatment can improve the tensile properties.
【学位授予单位】：沈阳航空航天大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG132.3;TG665

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