【摘要】：在未來先進(jìn)核裂變能——ADS擅變系統(tǒng)中,液態(tài)鉛鉍共晶合金(LBE)因其優(yōu)良的物理和化學(xué)性能成為加速器驅(qū)動次臨界系統(tǒng)(ADS)的散裂靶和冷卻劑的首要候選材料。在液態(tài)鉛鉍合金進(jìn)行循環(huán)冷卻的過程中會對反應(yīng)堆的結(jié)構(gòu)材料造成腐蝕,從而降低結(jié)構(gòu)材料的性能,減少使用壽命并增加核反應(yīng)堆的安全隱患。而空泡腐蝕是核電材料腐蝕失效行為之一,當(dāng)液態(tài)鉛鉍合金高速流動時會造成局部壓力起伏產(chǎn)生空化現(xiàn)象,隨著空泡的潰滅材料表面被破壞,從而發(fā)生空泡腐蝕。許多核反應(yīng)結(jié)構(gòu)部件的制造和裝配都是采取熔化焊的方式,如管道的接頭、主泵葉輪等。由于焊縫屬于鑄態(tài)組織,焊縫晶粒粗大、組織不均勻以及焊接殘余應(yīng)力等因素使其成為整個冷卻循環(huán)回路的薄弱區(qū)域。目前,國內(nèi)外對于核電材料的熔焊接頭在液態(tài)合金中的空蝕行為研究很少,因此研究其在液態(tài)鉛鉍合金中的空蝕行為及其機(jī)理具有重要的意義。304奧氏體不銹鋼和CLAM鋼因其優(yōu)良的性能可作為加速器驅(qū)動次臨界系統(tǒng)(ADS)中的結(jié)構(gòu)材料。本文利用自主設(shè)計的一套超聲波空蝕試驗裝置并聯(lián)合掃描電鏡(SEM)、原子力顯微鏡(AFM)等分析測試方法,研究了304奧氏體不銹鋼和CLAM鋼的母材和焊縫在550℃液態(tài)鉛鉍合金中的空蝕行為以及固溶處理對304奧氏體不銹鋼焊縫的空蝕行為的影響,并分析其空蝕機(jī)理。在550℃液態(tài)鉛鉍合金空蝕試驗中,304奧氏體不銹鋼及CLAM鋼的母材和焊縫的空蝕程度均隨著空蝕時間的延長而加劇。試驗結(jié)果表明,在空泡潰滅的沖擊下304奧氏體不銹鋼及CLAM鋼的母材和焊縫試樣表面均發(fā)生塑形變形和加工硬化,焊縫試樣表面的空蝕破壞明顯嚴(yán)重于母材,焊縫中的鐵素體優(yōu)先脫落,空蝕坑分別逐漸向奧氏體相和馬氏體相擴(kuò)展,試樣表面粗糙度明顯增大。CLAM鋼焊縫的抗空蝕性能明顯低于304奧氏體不銹鋼焊縫,這是由于馬氏體相屬于硬脆組織,雖然其可以通過位錯運動形成的塑性變形來吸收空泡潰滅所釋放的能量,但由于空泡潰滅時的沖擊非常大,馬氏體相容易發(fā)生脆性斷裂,進(jìn)一步加劇CLAM鋼的空蝕破壞。304奧氏體不銹鋼焊縫固溶處理后由于硬度提高,使得焊縫耐空泡潰滅沖擊的能力提高,從而減少了空蝕坑的產(chǎn)生和擴(kuò)大。另一方面,固溶處理使焊縫中大部分鐵素體相被固溶進(jìn)奧氏體中減少了空蝕源,進(jìn)一步提高了材料的抗空蝕性能。
[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，

本文編號：2270387