本文選題：Pb-Bi共晶合金 + 空泡腐蝕�。� 參考：《江蘇大學(xué)》2017年碩士論文

【摘要】：能源是決定當(dāng)前社會(huì)能否得到可持續(xù)發(fā)展的最重要因素,而核能的使用有助于緩解當(dāng)前能源困境。液態(tài)鉛鉍共晶合金(LBE)的抗輻射性強(qiáng),導(dǎo)熱性和安全性好,并且其中子學(xué)性能優(yōu)異,因此被廣泛用作核動(dòng)力加速器、次臨界驅(qū)動(dòng)系統(tǒng)(ADS)和鉛冷快堆的冷卻劑(LFR),但流動(dòng)的液態(tài)鉛鉍會(huì)對(duì)循環(huán)回路中的管道、儲(chǔ)存箱以及主泵葉輪材料造成嚴(yán)重的沖刷磨損腐蝕和空泡腐蝕。結(jié)構(gòu)鋼焊接接頭屬于鑄造組織,其內(nèi)部粗大的晶粒和焊后殘余應(yīng)力會(huì)進(jìn)一步加劇其在液態(tài)LBE中的空泡腐蝕。316L不銹鋼是奧氏體不銹鋼,擁有優(yōu)異的綜合力學(xué)性能是核反應(yīng)堆中應(yīng)用最廣泛的結(jié)構(gòu)材料,因此研究其耐空泡腐蝕性能有助于提高核反應(yīng)堆過流部件的耐腐蝕性能及為其服役壽命提供理論依據(jù)。本課題組自主設(shè)計(jì)了一套空泡腐蝕實(shí)驗(yàn)裝置,其中超聲波變幅桿的功率為3kw,頻率是19.2kHz,振幅為50μm。通過該空泡腐蝕裝置,對(duì)不同熱輸入的焊接接頭、預(yù)腐蝕后的焊接接頭、不同焊材的焊接接頭的空泡腐蝕行為進(jìn)行了研究。對(duì)不同熱輸入下的316L焊接接頭和其母材進(jìn)行80h的空泡腐蝕,結(jié)果顯示316L焊接接頭的耐空蝕性與焊接熱輸入的關(guān)系為焊接熱輸入越大,焊接接頭耐空蝕性越差。316L焊接接頭的耐空蝕性主要受奧氏體晶粒尺寸的影響,當(dāng)焊接熱輸入增大時(shí),焊縫區(qū)的奧氏體晶粒發(fā)生長(zhǎng)大,其抗空蝕能力較差。母材的耐空蝕性能普遍優(yōu)于焊縫,母材是鍛態(tài)組織,而焊縫是鑄態(tài)組織,其凝固模式是F-A型:鐵素體+奧氏體結(jié)晶,焊縫內(nèi)部形成了蠕蟲狀的鐵素體和粗大的奧氏體晶粒。316L焊接接頭在550℃液態(tài)LBE中進(jìn)行空泡腐蝕時(shí),試樣表面會(huì)生成雙氧化層,外氧化層為Fe_3O_4,內(nèi)氧化層為FeCr2O4,內(nèi)氧化的致密性高于外氧化層。外氧化層隨焊接熱輸入的增加而變厚,內(nèi)氧化層的厚度變化受熱輸入影響不大。探索空泡時(shí)間對(duì)316L焊接接頭空泡腐蝕行為的影響規(guī)律。在550℃液態(tài)LBE中對(duì)316L焊接接頭進(jìn)行不同時(shí)間的空泡腐蝕,觀測(cè)分析其空蝕后的表面SEM形貌和AFM形貌,結(jié)果顯示316L焊接接頭的表面粗糙度和腐蝕坑深度會(huì)隨著空蝕時(shí)間的增加而增加�？张莞g過程中,316L焊接接頭受空化應(yīng)力的作用,其表面會(huì)發(fā)生加工硬化,由于變形的晶粒迅速堆積在晶界處,相互之間的位錯(cuò)進(jìn)行了交割,空蝕后材料的表面硬度高于空蝕前材料的表面硬度。研究Ni元素對(duì)316L焊接接頭在550℃液態(tài)LBE中的空泡腐蝕的影響。結(jié)果表明焊接接頭中的Ni顆粒會(huì)彌散分布在晶粒內(nèi),與基體相的結(jié)合強(qiáng)度高,因此能夠顯著提升焊接接頭的耐空蝕能力。研究了預(yù)腐蝕對(duì)316L焊接接頭耐空泡腐蝕行為的影響。在200℃液態(tài)LBE預(yù)腐蝕80h后316L焊接接頭,其表面會(huì)形成一層薄的Fe_3O_4氧化層,在孕育期內(nèi)能有效抵擋空化應(yīng)力的沖擊作用,進(jìn)入上升期階段時(shí)反而降低了基體材料的抗空蝕能力。
[Abstract]:Energy is the most important factor to determine the sustainable development of the current society, and the use of nuclear energy can help alleviate the current energy predicament. Liquid lead-bismuth eutectic alloy (LBE) is widely used as a nuclear power accelerator because of its strong radiation resistance, good thermal conductivity and safety, and excellent subproperties. The subcritical drive system ADS) and the lead cooled fast reactor coolant LFRN, but the flowing liquid lead bismuth will cause serious erosion and cavitation corrosion on the pipes, storage tanks and impeller materials of the main pump. The welded joints of structural steel belong to cast structure, and the coarse grains inside them and the residual stress after welding will further aggravate the cavitation corrosion in liquid LBE. 316L stainless steel is austenitic stainless steel. Having excellent comprehensive mechanical properties is the most widely used structural material in nuclear reactors. Therefore, studying its cavitation corrosion resistance is helpful to improve the corrosion resistance of nuclear reactor overflowing components and provide theoretical basis for its service life. A cavitation corrosion experimental device was designed by our team, in which the power of ultrasonic horn is 3 kwk, the frequency is 19.2 kHz, and the amplitude is 50 渭 m. The cavitation corrosion behavior of welded joints with different heat input, pre-corroded joints and welded joints of different welding materials was studied by using the cavitation corrosion device. The cavitation corrosion of 316L welded joint and its base metal under different heat input was carried out for 80 h. The results showed that the relationship between cavitation corrosion resistance of 316L welded joint and welding heat input was the greater the welding heat input was. The cavitation corrosion resistance of welded joints is mainly affected by austenite grain size. When the welding heat input increases, the austenite grains in weld zone grow up, and the cavitation corrosion resistance of welded joints is poor. The cavitation corrosion resistance of the base metal is generally superior to that of the weld metal. The base metal is a forged structure, while the weld metal is a cast structure, and its solidification mode is F-A: ferrite austenite crystallization. When worm-like ferrite and coarse austenitic grain .316L welded joints are formed inside the weld, when cavitation corrosion is carried out in liquid LBE at 550 鈩，

本文編號(hào)：1837400