本文選題：奧氏體不銹鋼 + 晶間腐蝕　； 參考：《鄭州大學(xué)》2017年碩士論文

【摘要】：石油工業(yè)在拉動(dòng)經(jīng)濟(jì)增長(zhǎng)和日常人民生活方面具有很重要的作用,在石油開(kāi)采過(guò)程中,使用的無(wú)磁鉆鋌用奧氏體不銹鋼材料因其具有良好的物理性能、力學(xué)性能和腐蝕性能而得到了廣泛的應(yīng)用。由于鉆鋌材料所處環(huán)境介質(zhì)的腐蝕性和材料服役過(guò)程中的特殊性,因此研究奧氏體不銹鋼的腐蝕行為對(duì)于正確評(píng)判不銹鋼腐蝕敏感性及優(yōu)化材料生產(chǎn)工藝具有重要的意義。電化學(xué)動(dòng)電位再活化法(EPR)常用來(lái)評(píng)價(jià)奧氏體不銹鋼的晶間腐蝕敏感性;嘗試采用電化學(xué)阻抗技術(shù)(EIS)來(lái)檢測(cè)奧氏體不銹鋼的腐蝕性能,其測(cè)試結(jié)果在譜圖中表現(xiàn)為阻抗弧的變化,可以提供較多界面電荷轉(zhuǎn)移信息,為材料腐蝕性能的測(cè)試提供理論基礎(chǔ)。本文采用電化學(xué)動(dòng)電位再活化法、電化學(xué)阻抗分析、動(dòng)電位極化法、Cu-H2SO4-CuSO4法、OM觀察、SEM觀察等研究了不同固溶處理和敏化處理對(duì)奧氏體不銹鋼組織及腐蝕行為的影響,確定該不銹鋼合適固溶處理工藝和晶間腐蝕的敏感溫度;采用草酸浸蝕方法和電化學(xué)阻抗技術(shù)檢測(cè)不銹鋼晶間腐蝕發(fā)生和發(fā)展過(guò)程,初步建立晶間腐蝕的電化學(xué)等效電路,分析了等效電路參數(shù)與晶間腐蝕敏感性程度的相關(guān)性。研究結(jié)果表明:鍛態(tài)高氮奧氏體不銹鋼組織中存在大量的孿晶,組織中存在顆粒狀Cr、V的氮化物。當(dāng)試樣在950-1100℃固溶處理30min后,顯微組織為完全奧氏體組織,組織晶粒尺寸隨固溶溫度的升高而變大,晶粒也變得越來(lái)越均勻。經(jīng)過(guò)相同敏化處理后,其再活化率R隨著固溶處理溫度升高而降低,在腐蝕液中試樣的容抗弧半徑逐漸增大。當(dāng)固溶溫度為1100℃時(shí),阻抗譜的容抗弧半徑最大,其耐腐蝕性能也最好。在10%草酸恒電流浸蝕試驗(yàn)中,隨著浸蝕時(shí)間的增加,試樣的腐蝕程度增加,浸蝕90s時(shí)試樣表現(xiàn)出嚴(yán)重的晶界腐蝕,晶界有腐蝕溝,大部分晶粒被腐蝕溝包圍。這說(shuō)明浸蝕時(shí)間不同,晶間腐蝕的發(fā)展程度不同,晶間腐蝕的過(guò)程和浸蝕時(shí)間有一定的依賴關(guān)系。高氮奧氏體不銹鋼經(jīng)過(guò)相同固溶處理后,在700℃、800℃、900℃敏化溫度處理6h;敏化溫度為800℃時(shí),試樣的顯微晶粒尺寸最小,晶粒最為均勻。800℃敏化處理試樣EPR的再活化率最大,其腐蝕形貌與其他敏化溫度相比較為嚴(yán)重;EIS曲線中,敏化溫度800℃處理的試樣在腐蝕介質(zhì)中的容抗弧半徑最小,其耐腐蝕性能較差。高氮奧氏體不銹鋼在800℃敏化不同時(shí)間,隨著敏化時(shí)間的增長(zhǎng),奧氏體晶粒尺寸逐漸增加,敏化12h時(shí),孿晶消失,基體為全奧氏體組織;隨著敏化時(shí)間的增加,晶界上析出物開(kāi)始增加,同時(shí)晶粒內(nèi)部開(kāi)始析出類(lèi)珠光體組織層片狀的Cr2N,同時(shí)試樣的再活化率隨著敏化時(shí)間的延長(zhǎng)而增加,試樣的晶間腐蝕敏感性增加。通過(guò)改變浸泡時(shí)間、pH值、NaCl溶液濃度等介質(zhì)條件,表明隨著浸泡時(shí)間的增長(zhǎng)和NaCl溶液濃度增加,不銹鋼的耐點(diǎn)蝕敏感性降低,隨著NaCl溶液pH值的增加,不銹鋼的耐點(diǎn)蝕敏感性升高。通過(guò)研究不同固溶處理和敏化處理參數(shù)對(duì)高氮奧氏體不銹鋼組織和腐蝕性能的影響,該Cr-Mn-N高氮奧氏體不銹鋼合適的固溶溫度為1100℃,腐蝕敏感溫度為800℃,并且在一定范圍內(nèi)隨著敏化時(shí)間的增加,其耐腐蝕性能降低,材料的力學(xué)性能下降,在材料服役過(guò)程中應(yīng)避免在敏化溫度范圍內(nèi)長(zhǎng)期使用。
[Abstract]:The oil industry plays an important role in stimulating economic growth and daily life. In the process of oil mining, the austenitic stainless steel material used for non magnetic drill collars has been widely used because of its good physical properties, mechanical properties and corrosion properties. It is of great significance to study the corrosion behavior of austenitic stainless steel for evaluating the corrosion sensitivity of stainless steel and optimizing the material production process. Electrochemical potential reactivation (EPR) is used to evaluate the intergranular corrosion sensitivity of austenitic stainless steel. The electrochemical impedance technique (EI) is used. S) to detect the corrosion properties of austenitic stainless steel. The test results show the change of impedance arc in the spectrum, which can provide more interface charge transfer information and provide a theoretical basis for testing the corrosion properties of materials. In this paper, electrochemical potential reactivation, electrochemical impedance analysis, dynamic potential polarization, Cu-H2SO4-CuSO4 method, OM view are used in this paper. The effects of different solid solution treatment and sensitization treatment on the microstructure and corrosion behavior of austenitic stainless steel were investigated by SEM observation, and the appropriate solution treatment process and the sensitive temperature of intergranular corrosion were determined. The process of intercrystalline corrosion and the development process of stainless steel intergranular corrosion were detected by oxalic acid etching and electrochemical impedance technology. The correlation between the equivalent circuit parameters and the degree of intercrystalline corrosion sensitivity is analyzed. The results show that there are a large number of twins in the forged high nitrogen austenitic stainless steel structure, and the granular Cr, V nitrogen compounds exist in the tissue. The microstructure is the complete austenite group when the sample is treated with 30min at 950-1100 C. After the same sensitization treatment, the reactivation rate R decreases with the increase of the solution treatment temperature and the radius of the resistance arc of the specimen in the corrosion solution. When the solid solution temperature is 1100, the resistance arc radius of the impedance spectrum is the largest, and its corrosion resistance is resistant to corrosion. In the 10% oxalic acid constant current immersion test, the corrosion degree of the sample increases with the increase of the etching time. The specimen shows a serious grain boundary corrosion, the grain boundary has a corrosion ditch, and most of the grain is surrounded by corrosion ditch. This indicates that the etching time is different, the development degree of intergranular corrosion is different, the process of intergranular corrosion and the process of intercrystalline corrosion are explained. The etching time has a certain dependence. After the same solution treatment, the high nitrogen austenitic stainless steel is treated at 700 C, 800 C and 900 C sensitized temperature for 6h. When the sensitization temperature is 800 C, the microcrystalline grain size of the sample is the smallest, and the most homogeneous.800 C sensitized sample EPR has the greatest reactivation rate, and the corrosion morphology and other sensitization temperature phase In the EIS curve, the resistance arc radius of the sample treated at 800 centigrade temperature is the smallest and its corrosion resistance is poor. The austenite grain size of high nitrogen austenitic stainless steel increases with the sensitization time at 800 centigrade, and the twins disappears and the matrix is full austenite when sensitized 12h. With the increase of sensitization time, the precipitates on the grain boundary begin to increase, and the Cr2N of the lamellar pearlite like layer begins to be precipitated inside the grain. At the same time, the reactivation rate of the sample increases with the prolongation of the sensitization time, and the intergranular corrosion sensitivity of the sample increases. By changing the medium conditions such as the soaking time, the pH value and the concentration of NaCl solution, it is shown that the sample has the same medium. The pitting resistance of stainless steel decreased with the increase of soaking time and the increase of NaCl solution concentration. With the increase of pH value of NaCl solution, the resistance to pitting resistance of stainless steel increased. The effect of different solution treatment and sensitization parameters on Microstructure and corrosion properties of high nitrogen austenitic stainless steel was studied, and the Cr-Mn-N high nitrogen austenitic stainless steel was studied. The suitable solution temperature is 1100 C and the corrosion sensitive temperature is 800. And with the increase of the sensitization time in a certain range, the corrosion resistance of the material is reduced and the mechanical properties of the material decrease. The long-term use of the sensitized temperature should be avoided in the service process of the material.

【學(xué)位授予單位】：鄭州大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類(lèi)號(hào)】：TE921.2;TG142.71

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