Studying the Mechanism behind Stress Corrosion Cracking of Non Sensitized 304L Austenitic Stainless Steel
Studying the Mechanism behind Stress Corrosion Cracking of Non Sensitized 304L Austenitic Stainless Steel
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非敏化304L奥氏体不锈钢应力腐蚀开裂机理研究
DOI：
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发表时间：
2013
期刊：
影响因子：
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通讯作者：
V. Kain
中科院分区：
文献类型：
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作者：
Swati Ghosh Acharyya;M. Kumar;V. Kain
鉴于表面加工操作的重要作用，本文研究了非敏化304L不锈钢（SS）部件对应力腐蚀开裂（SCC）的敏感性。工厂经验表明，非敏化304L不锈钢构件断口表面无碳化物析出迹象。然而，在深度约为100 μm的表面出现了高密度的滑移带，并在表面附近产生了高拉伸残余应力。目前的研究已经确定，SCC敏感性增加的主要原因是表面附近的严重塑性变形和高强度的拉伸残余应力，这是加工和磨削等表面精加工操作的结果。在本研究中，溶液退火304L不锈钢经受了a)表面加工操作，如机加工和磨削，b)大量变形操作，如10%冷轧操作。材料在不同的条件下，然后进行详细的a)微观结构表征，b)电化学表征和c)测试，以确定应力腐蚀开裂敏感性。304L奥氏体不锈钢的体变形和表面变形导致的显微组织的明显差异被强调，并与对应力腐蚀开裂的敏感性相关。采用接触电阻（CER）和电化学阻抗谱测量技术，在与循环回路系统连接的高压灭菌器中，在300°C和10 MPa的高纯水（电导率< 0.1 μ cm-1）中，原位研究了表面加工对304L不锈钢表面高温（300°C和10 MPa）氧化物性质和组成的影响。结果突出了表面加工材料的氧化行为与溶液退火材料在比电阻率和低频Warburg阻抗方面的明显差异。
The susceptibility of non sensitized 304L stainless steel (SS) components towards stress corrosion cracking (SCC) has been studied here in the light of the significant role played by surface working operations. The plant experience shows that the fracture surfaces of non sensitized 304L stainless steel components have no signs of carbide precipitation. However, heavy plastic deformation has been evidenced in the form of high density of slip bands on the surface up to a depth of about 100 μm with high tensile residual stresses near the surface. The present study has established that the primary cause of the increase in SCC susceptibility is the heavy plastic deformation near the surface and high magnitude of tensile residual stresses which is a consequence of the surface finishing operations like machining and grinding. In this study, solution annealed 304L stainless steel has been subjected to a) surface working operations like machining and grinding and b) bulk deformation operations such as 10 % cold rolling operation. The materials in different conditions where then subjected to detailed a) microstructural characterisation, b) electrochemical characterisation and c) tests for determining the stress corrosion cracking susceptibility. The distinct differences in the micro structure as a result of bulk deformation vs. surface deformation of 304L austenitic stainless steel were highlighted and correlated to the susceptibility towards stress corrosion cracking. The effect of surface working on the nature and composition of high temperature (300 °C and 10 MPa) oxide formed on 304L stainless steel has been studied in-situ by contact electric resistance (CER) and electrochemical impedance spectroscopy measurements using controlled distance electrochemistry technique in high purity water (conductivity < 0.1 μScm-1) at 300 °C and 10 MPa in an autoclave connected to a recirculation loop system. The results highlighted the distinct differences in the oxidation behaviour of surface worked material as compared to solution annealed material in terms of specific resistivity and low frequency Warburg impedance.