本文選題：海洋環(huán)境　切入點(diǎn)：不銹鋼　出處：《上海材料研究所》2017年碩士論文　論文類型：學(xué)位論文

【摘要】：國家海洋開發(fā)戰(zhàn)略的實(shí)施需要海洋工程裝備提供質(zhì)量保證,而海洋工程的發(fā)展需要高性能材料作為支撐。本工作主要采用電化學(xué)方法研究了兩種不銹鋼材料,Z2CND18-12N奧氏體不銹鋼和S32760雙相不銹鋼,在模擬海洋環(huán)境中的局部腐蝕行為,包括點(diǎn)腐蝕、縫隙腐蝕及應(yīng)力腐蝕破裂(Stress Corrosion Cracking,SCC)。根據(jù)海洋環(huán)境條件,選取的模擬環(huán)境有按照ASTM標(biāo)準(zhǔn)制備的人造海水和不同溫度和不同濃度的NaCl溶液,其中不同溫度條件為3℃、30℃及60℃,NaCl溶液選取的濃度有接近海水濃度的3.5%NaCl溶液及模擬蒸發(fā)濃縮情況下的10%NaCl溶液。主要工作內(nèi)容及結(jié)論如下:(1)研究了人造海水和3.5%NaCl溶液中,S32760雙相不銹鋼和Z2CND18-12N奧氏體不銹鋼動電位陽極極化曲線行為,S32760在兩種溶液中表現(xiàn)出相似的動電位極化行為,鈍化區(qū)較寬,點(diǎn)蝕電位較高,在+1000mV(相對于飽和甘汞電極SCE,下同)以上;Z2CND18-12N奧氏體不銹鋼在兩種溶液中極化行為相近,均表現(xiàn)為較大的亞穩(wěn)態(tài)波動后點(diǎn)蝕擊穿。研究了兩種材料分別在3℃、30℃及60℃的3.5%和10%NaCl溶液條件下的點(diǎn)蝕行為,S32760雙相不銹鋼表現(xiàn)出優(yōu)秀的點(diǎn)蝕抗力,點(diǎn)蝕電位在+1000mV左右,但是在60℃時(shí)出現(xiàn)較明顯的亞穩(wěn)態(tài)波動;Z2CND18-12N奧氏體不銹鋼在低溫3℃下表現(xiàn)出與S32760接近的點(diǎn)蝕抗力,低溫下耐點(diǎn)蝕性能優(yōu)良,但是溫度升高導(dǎo)致點(diǎn)蝕抗力顯著下降,在30℃和60℃測試時(shí),極化曲線上有明顯的點(diǎn)蝕擊穿,試樣上出現(xiàn)明顯的點(diǎn)蝕坑,耐點(diǎn)蝕性能不及S32760雙相不銹鋼。NaCl溶液濃度增大時(shí)點(diǎn)蝕電位下降。(2)采用動電位極化、臨界點(diǎn)蝕溫度(Critical Pitting Temperature,CPT)測試及腐蝕形貌觀察方法對比性地研究了材料的點(diǎn)腐蝕行為,結(jié)果表明應(yīng)采用多種方法綜合評價(jià)較為合理。例如S32760雙相不銹鋼在60℃下,點(diǎn)蝕電位雖接近+1000mV,但是在掃描電鏡下能觀察到亞穩(wěn)態(tài)點(diǎn)蝕形貌,此時(shí)已有點(diǎn)蝕傾向。CPT測試能較好地反映高耐蝕性材料的耐點(diǎn)蝕性能及其對溫度的敏感性。(3)S32760雙相不銹鋼的縫隙腐蝕抗力明顯高于Z2CND18-12N,S32760在3℃、30℃及60℃的3.5%和10%NaCl溶液條件下再鈍化電位均高于+800mV。Z2CND18-12N不銹鋼的縫隙腐蝕抗力較差,在低溫3℃的兩種NaCl溶液中及30℃3.5%NaCl溶液中未發(fā)生縫隙腐蝕,而在30℃濃度更高的10%NaCl溶液及溫度升高到60℃時(shí)均對縫隙腐蝕敏感。與點(diǎn)蝕結(jié)果對比,Z2CND18-12N縫隙腐蝕抗力低于其點(diǎn)蝕抗力,溶液環(huán)境較為苛刻時(shí),在較低電位下易發(fā)生縫隙腐蝕。(4)采用慢應(yīng)變速率試驗(yàn)(SSRT)和電化學(xué)測控相結(jié)合的方法研究了電位對兩種材料在30℃的3.5%NaCl溶液環(huán)境中SCC的影響。Z2CND18-12N奧氏體不銹鋼在+100mV時(shí)發(fā)生陽極溶解,在+400m V及+600mV時(shí)陽極溶解顯著,并伴有SCC裂紋出現(xiàn),該SCC機(jī)理應(yīng)該是陽極溶解;較正電位容易引發(fā)Z2CND18-12N發(fā)生點(diǎn)腐蝕及SCC。S32760雙相不銹鋼在較負(fù)電位時(shí)發(fā)生SCC,測得臨界電位在-800mV與-900mV之間,在-900mV電位以及低于-900mV時(shí)均會發(fā)生SCC;電位為+600mV時(shí),S32760不發(fā)生SCC;該材料發(fā)生SCC的機(jī)理應(yīng)屬于氫致開裂。
[Abstract]:The implementation of the national marine development strategy of ocean engineering equipment to provide quality assurance, and development of marine engineering high performance materials as support. This work mainly adopts the electrochemical method of two kinds of stainless steel, austenitic stainless steel Z2CND18-12N and S32760 dual phase stainless steel, the local corrosion behavior in simulated marine environment, including the point of corrosion. And the stress corrosion cracking of crevice corrosion (Stress Corrosion Cracking, SCC). According to the marine environmental conditions, simulation environment selection according to the ASTM standard preparation of artificial seawater and different temperature and different concentration of NaCl solution, the different temperature is 3 DEG, 30 DEG and 60 DEG C, the concentration of NaCl solution selected 10%NaCl 3.5%NaCl of a solution close to seawater concentration and simulated evaporation conditions. The main contents and conclusions are as follows: (1) study on the artificial seawater and 3.5% NaCl solution, S3 2760 duplex stainless steel and Z2CND18-12N austenitic stainless steel potentiodynamic anodic polarization curve, S32760 in two kinds of solution showed a similar polarization behavior, passivation region is wide, the pitting potential is higher in +1000mV (relative to the saturated calomel electrode SCE, the same below) above; Z2CND18-12N austenitic stainless steel in the vicinity of two kinds of solution of polarization behavior showed the fluctuation of metastable pitting breakdown. After the study of two kinds of materials respectively at 3 C, 30 C and 60 C pitting 3.5% and 10%NaCl solution under the condition of S32760 dual phase stainless steel exhibits excellent corrosion resistance and pitting potential of about +1000mV, but at 60 DEG C when metastable fluctuations obviously; Z2CND18-12N austenitic stainless steel at low temperature under 3 DEG C and corrosion resistance of S32760 showed a close, low temperature corrosion resistance is excellent, but the increasing temperature pitting resistance obviously under Drop in 30 degrees and 60 degrees test, there are obvious pitting breakdown on the polarization curves and corrosion pits appeared in the sample, the concentration of.NaCl solution increases when the decrease in pitting potential pitting resistance of duplex stainless steel is less than S32760. (2) by potentiodynamic polarization, critical pitting temperature (Critical Pitting, Temperature, CPT) test the corrosion morphology observation method and the comparative study of corrosion behavior of the materials. The results show that we should adopt various methods of comprehensive evaluation more reasonable. For example, S32760 duplex stainless steel under 60 degrees, although the pitting potential close to +1000mV, but under the scanning electron microscope to observe the metastable pitting morphology, while the pitting tendency of.CPT testing can be better the high corrosion resistance of materials corrosion resistance and sensitivity to temperature. (3) the crevice corrosion resistance of S32760 duplex stainless steel is higher than that of Z2CND18-12N and S32760 at 3 C, 30 C and 60 C 3.5 The crevice corrosion resistance and poor% 10%NaCl solution under the condition of repassivation potential was higher than that of +800mV.Z2CND18-12N stainless steel, corrosion occurred in two NaCl solution at low temperature 3 DEG C and 30 C in 3.5%NaCl solution, 10%NaCl solution and the temperature of 30 DEG C higher concentration increased to 60 DEG are sensitive to crevice corrosion. Contrast the results of Z2CND18-12N and pitting, crevice corrosion resistance than the pitting resistance, harsh environmental solution, prone to crevice corrosion at low potential. (4) using slow strain rate test (SSRT) method and electrochemical measurement on the combination of the two materials in the potential effects of 30 DEG 3.5%NaCl in solution SCC.Z2CND18-12N austenitic stainless steel anode dissolved in +100mV, +400m and V in +600mV and SCC with significant anodic dissolution, cracks, the mechanism of SCC should be relatively easy to anodic dissolution; positive lead Z2CND18-12N point corrosion and SCC.S32760 duplex stainless steel SCC occurs at a negative potential, the measured critical potential between -800mV and -900mV, SCC in -900mV and -900mV were lower than the potential will; the potential of +600mV, S32760 SCC SCC does not occur; mechanism of the material should belong to hydrogen induced cracking.

【學(xué)位授予單位】：上海材料研究所
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TG178

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