Stress Corrosion Cracking—Crevice Interaction in Austenitic Stainless Steels Characterized By Acoustic Emission
Stress Corrosion Cracking—Crevice Interaction in Austenitic Stainless Steels Characterized By Acoustic Emission
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DOI：
10.1007/s11661-010-0442-9
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发表时间：
2011-02
期刊：
影响因子：
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通讯作者：
H. Leinonen;T. Schildt;H. Hänninen
中科院分区：
文献类型：
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作者：
H. Leinonen;T. Schildt;H. Hänninen
采用恒载荷法和聚合物(PTFE)缝隙成形器研究了奥氏体EN1.4301(AISI 304)和EN1.4404(AISI 316L)不锈钢的应力腐蚀敏感性，研究了缝隙对应力腐蚀敏感性的影响。在开路腐蚀电位(OCP)和电化学极化下，分别在373K(100°C)下的50%CaCl2和353K(80°C)下的0.1MNaC中进行了单轴主动载荷试验。采用∆滤波和线性定位技术进行声发射(AE)分析，对点蚀、缝隙和应力腐蚀进行了表征和识别。利用幅度、持续时间、上升时间、计数和能量等声发射参数的相关性来识别不同类型的腐蚀。用声发射监测了恒定主动载荷/缝隙形成器引起的缝隙腐蚀和应力腐蚀的阶段。在测试的早期阶段，检测到一些低幅度的声发射活动。在稳态阶段，声发射活动较低，到测试结束时，随着脉冲幅度的增加，声发射活动增加。声发射信号与腐蚀损伤之间有很好的相关性。虽然缝隙腐蚀和应力腐蚀引起的声发射信号略有重叠，但它们与显微特征和应力-应变数据之间存在很好的相关性。特别是，在恒定载荷条件下，声发射信号的活性在应力腐蚀试验的早期和后期增加，对应于所测得的试件稳态蠕变应变率的变化。恒定活性载荷/缝隙形成试验结果表明，即使在低温温和的氯化物溶液中，缝隙也能引发应力腐蚀开裂。根据应力腐蚀开裂的力学模型，认为应力腐蚀开裂的速率决定步骤是选择性溶解产生空位，而稳态蠕变应变区中低活度的Ae相支持这一过程。
Stress corrosion cracking (SCC) susceptibility of austenitic EN1.4301 (AISI 304) and EN1.4404 (AISI 316L) stainless steels was studied using the constant load method and polymer (PTFE) crevice former in order to study the effects of crevice on SCC susceptibility. The uniaxial active loading tests were performed in 50 pct CaCl2 at 373 K (100 °C) and in 0.1 M NaCl at 353 K (80 °C) under open-circuit corrosion potential (OCP) and electrochemical polarization. Pitting, crevice, and SCC corrosion were characterized and identified by acoustic emission (AE) analysis using ∆tfiltering and the linear locationing technique. The correlation of AE parameters including amplitude, duration, rise time, counts, and energy were used to identify the different types of corrosion. The stages of crevice corrosion and SCC induced by constant active load/crevice former were monitored by AE. In the early phase of the tests, some low amplitude AE activity was detected. In the steady-state phase, the AE activity was low, and toward the end of the test, it increased with the increasing amplitude of the impulses. AE allowed a good correlation between AE signals and corrosion damage. Although crevice corrosion and SCC induced AE signals overlapped slightly, a good correlation between them and microscopical characterization and stress-strain data was found. Especially, the activity of AE signals increased in the early and final stages of the SCC experiment under constant active load conditions corresponding to the changes in the measured steady-state creep strain rate of the specimen. The results of the constant active load/crevice former test indicate that a crevice can initiate SCC even in the mild chloride solution at low temperatures. Based on the mechanistic model of SCC, the rate determining step in SCC is thought to be the generation of vacancies by selective dissolution, which is supported by the low activity phase of AE during the steady-state creep strain rate region.