| 引用本文: | 刘肖,王理,孙永铎,舒茗,吴军.内壁强化对TA16钛合金传热管断裂韧度的影响[J].中国表面工程,2023,36(3):205~213 |
| LIU Xiao,WANG Li,SUN Yongduo,SHU Ming,WU Jun.Effect of Inner Wall Strengtheing on Fracture Toughness of TA16 Titanium Alloy Tubes[J].China Surface Engineering,2023,36(3):205~213 |
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| 摘要: |
| 采用 TA16 传热管制备的直流蒸汽发生器是新一代核动力装置的核心部件。为提高管材的内壁质量，目前采用内绞、 喷砂等数道表面加工程序，生产成本大幅升高。为简化工艺流程，降低生产成本，开展针对 TA16 管材的内壁强化技术研究。 同时为了确定内壁强化对管材断裂韧性的影响，提出一种含双边轴向裂纹管(DEAT)试样，通过弹塑性有限元分析建立 DEAT 试样的应力强度因子 K 和 J 积分的计算表达式，通过建立的试验方法完成内壁强化前后 TA16 传热管的 J-R 曲线测试，获得内壁强化前后 TA16 传热管的断裂韧性参数。试验后采用 SEM、EBSD、TEM 及纳米压痕分析内壁强化对管材微观组织和性能的影响。研究结果表明：强化后 TA16 管内壁从表面沿径向形成 100~200 μm 的纳米超细晶区和孪晶变形区，显著提高了管材的内壁质量，但由于表层的硬度升高，导致传热管的断裂韧度整体水平有所下降。研究结果可为 TA16 管材的质量提升、 安全性评价及性能退化评估奠定技术基础。 |
| 关键词: TA16 钛合金 传热管 内壁强化 断裂韧度 组织演变 |
| DOI：10.11933/j.issn.1007?9289.20220719001 |
| 分类号:TL341 |
| 基金项目: |
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| Effect of Inner Wall Strengtheing on Fracture Toughness of TA16 Titanium Alloy Tubes |
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LIU Xiao, WANG Li, SUN Yongduo, SHU Ming, WU Jun
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Science and Technology on Reactor Fuel and Materials Laboratory, Nuclear Power Institute of China,Chengdu 610213 , China
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| Abstract: |
| Titanium alloys have been widely used in the new generation of micro nuclear power reactors because of their high specific strength, excellent corrosion resistance, and nonmagnetic properties. In particular, steam generator heat transfer tubes are prepared with TA16 titanium alloy. To improve space utilization and heat transfer efficiency, the heat transfer tubes are specifically designed as thick-walled tubes with small diameter. However, in the existing rolling process, the inner wall of the tubes is prone to produce serrated defects and micro-cracks, greatly reducing the yield of the tubes. To further improve the inner wall quality of the heat transfer tubes, several surface processing procedures, such as internal rolling and sand blasting, have been adopted, which have greatly increased the production cost. In order to simplify the technical process and reduce the production cost, a contact reinforcement treatment was completed in the heat transfer tubes, which is a new technology developed from hole extrusion strengthening. An elastic-plastic deformation area was formed on the inner wall by high-strength ordered small bulges extrusion mandrel. The increased dislocation density with the changing microstructure formed a residual compressive stress distribution area that is beneficial to the surface property of the tubes and effectively improves the quality of the inner wall of the alloy tubes. Furthermore, as the pressure boundary to prevent radioactive substances from leaking out, the fracture toughness of TA16 heat transfer tube is a key indicator to evaluate the structural integrity and ensure the safe operation of the reactor. For obtaining the fracture toughness of TA16 titanium alloy tubes after the inner wall strengthening process, a kind of double-edged axial-notched tube(DEAT) specimen was proposed for the fracture toughness test of the heat transfer tubes in this work. Expressions for stress intensity factor K and J integral of DEAT specimen were established via elastic-plastic finite element analysis. The J-R curves for the strengthened and blank DEAT specimens were realized by the established method, and the parameters of fracture toughness were obtained. The effect of inner wall strengthening on the microstructure and properties of TA16 titanium alloy tubes was analyzed via scanning electron microscopy, electron backscattered diffraction, transmission electron microscopy, and nano-indentation test. The results show that, the inner wall of the strengthened TA16 alloy tube results in a thickness of 100-200 μm of a nanocrystalline region and twin deformation zone from the inner surface along the radial direction, which significantly improves the inner wall quality. Additionally, the hardness of the surface layer increases, leading to a decrease in the fracture toughness. In the process of surface strengthening, the influence of rolling reduction and feeding speed on the inner wall strengthening of the heat transfer tubes require further investigation. It is also necessary to consider the plasticity and toughness while improving the surface quality. This research method can promote the continuous improvement of the inner wall strengthening of TA16 tubes and other small-diameter tubes, which will lay a technical foundation for the quality improvement, safety evaluation, and performance degradation evaluation of TA16 heat transfer tubes. |
| Key words: TA16 Titanium alloy heat transfer tube inner wall strengthening fracture toughness microstructure change |
