液态Pb-Bi合金中304奥氏体不锈钢及CLAM钢焊接接头的空蚀行为研究
发布时间：2018-10-14 11:59
【摘要】：在未来先进核裂变能——ADS擅变系统中,液态铅铋共晶合金(LBE)因其优良的物理和化学性能成为加速器驱动次临界系统(ADS)的散裂靶和冷却剂的首要候选材料。在液态铅铋合金进行循环冷却的过程中会对反应堆的结构材料造成腐蚀,从而降低结构材料的性能,减少使用寿命并增加核反应堆的安全隐患。而空泡腐蚀是核电材料腐蚀失效行为之一,当液态铅铋合金高速流动时会造成局部压力起伏产生空化现象,随着空泡的溃灭材料表面被破坏,从而发生空泡腐蚀。许多核反应结构部件的制造和装配都是采取熔化焊的方式,如管道的接头、主泵叶轮等。由于焊缝属于铸态组织,焊缝晶粒粗大、组织不均匀以及焊接残余应力等因素使其成为整个冷却循环回路的薄弱区域。目前,国内外对于核电材料的熔焊接头在液态合金中的空蚀行为研究很少,因此研究其在液态铅铋合金中的空蚀行为及其机理具有重要的意义。304奥氏体不锈钢和CLAM钢因其优良的性能可作为加速器驱动次临界系统(ADS)中的结构材料。本文利用自主设计的一套超声波空蚀试验装置并联合扫描电镜(SEM)、原子力显微镜(AFM)等分析测试方法,研究了304奥氏体不锈钢和CLAM钢的母材和焊缝在550℃液态铅铋合金中的空蚀行为以及固溶处理对304奥氏体不锈钢焊缝的空蚀行为的影响,并分析其空蚀机理。在550℃液态铅铋合金空蚀试验中,304奥氏体不锈钢及CLAM钢的母材和焊缝的空蚀程度均随着空蚀时间的延长而加剧。试验结果表明,在空泡溃灭的冲击下304奥氏体不锈钢及CLAM钢的母材和焊缝试样表面均发生塑形变形和加工硬化,焊缝试样表面的空蚀破坏明显严重于母材,焊缝中的铁素体优先脱落,空蚀坑分别逐渐向奥氏体相和马氏体相扩展,试样表面粗糙度明显增大。CLAM钢焊缝的抗空蚀性能明显低于304奥氏体不锈钢焊缝,这是由于马氏体相属于硬脆组织,虽然其可以通过位错运动形成的塑性变形来吸收空泡溃灭所释放的能量,但由于空泡溃灭时的冲击非常大,马氏体相容易发生脆性断裂,进一步加剧CLAM钢的空蚀破坏。304奥氏体不锈钢焊缝固溶处理后由于硬度提高,使得焊缝耐空泡溃灭冲击的能力提高,从而减少了空蚀坑的产生和扩大。另一方面,固溶处理使焊缝中大部分铁素体相被固溶进奥氏体中减少了空蚀源,进一步提高了材料的抗空蚀性能。
[Abstract]:In the future advanced nuclear fission energy (ADS) system, liquid lead-bismuth eutectic alloy (LBE) has become the primary candidate for spallation targets and coolant for accelerator driven subcritical system (ADS) because of its excellent physical and chemical properties. In the process of circulating cooling of liquid lead-bismuth alloy, the structural materials of the reactor will be corroded, which will reduce the performance of the structural materials, reduce the service life and increase the safety risks of the nuclear reactors. Cavitation corrosion is one of the corrosion failure behaviors of nuclear power materials. When liquid lead-bismuth alloy flows at high speed, cavitation will occur due to local pressure fluctuation. Many nuclear reaction components are fabricated and assembled by melting welding, such as pipe joints, main pump impellers and so on. Because the weld belongs to the as-cast structure, the grain size of the weld is coarse, the microstructure is uneven and the welding residual stress makes it become the weak area of the whole cooling cycle loop. At present, there is little research on cavitation corrosion behavior of fusion welded joints of nuclear power materials in liquid alloys at home and abroad. Therefore, it is of great significance to study the cavitation corrosion behavior and its mechanism in liquid lead-bismuth alloys. 304 austenitic stainless steel and CLAM steel can be used as structural materials in accelerator driven subcritical system (ADS) because of their excellent properties. In this paper, a set of ultrasonic cavitation test equipment designed by ourselves and combined with scanning electron microscope (SEM) (SEM), atomic force microscope (AFM) and other analytical and testing methods are used in this paper. The cavitation corrosion behavior of the base metal and weld of 304 austenitic stainless steel and CLAM steel in liquid lead-bismuth alloy at 550 鈩，
本文编号：2270387
[Abstract]:In the future advanced nuclear fission energy (ADS) system, liquid lead-bismuth eutectic alloy (LBE) has become the primary candidate for spallation targets and coolant for accelerator driven subcritical system (ADS) because of its excellent physical and chemical properties. In the process of circulating cooling of liquid lead-bismuth alloy, the structural materials of the reactor will be corroded, which will reduce the performance of the structural materials, reduce the service life and increase the safety risks of the nuclear reactors. Cavitation corrosion is one of the corrosion failure behaviors of nuclear power materials. When liquid lead-bismuth alloy flows at high speed, cavitation will occur due to local pressure fluctuation. Many nuclear reaction components are fabricated and assembled by melting welding, such as pipe joints, main pump impellers and so on. Because the weld belongs to the as-cast structure, the grain size of the weld is coarse, the microstructure is uneven and the welding residual stress makes it become the weak area of the whole cooling cycle loop. At present, there is little research on cavitation corrosion behavior of fusion welded joints of nuclear power materials in liquid alloys at home and abroad. Therefore, it is of great significance to study the cavitation corrosion behavior and its mechanism in liquid lead-bismuth alloys. 304 austenitic stainless steel and CLAM steel can be used as structural materials in accelerator driven subcritical system (ADS) because of their excellent properties. In this paper, a set of ultrasonic cavitation test equipment designed by ourselves and combined with scanning electron microscope (SEM) (SEM), atomic force microscope (AFM) and other analytical and testing methods are used in this paper. The cavitation corrosion behavior of the base metal and weld of 304 austenitic stainless steel and CLAM steel in liquid lead-bismuth alloy at 550 鈩，
本文编号：2270387
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