摘要
采用动电位极化技术、慢应变速率拉伸试验和扫描电镜观察研究了有、无硫酸盐还原菌(SRB)情况下X70管线钢及焊缝在近中性p H溶液(NS4)中的应力腐蚀行为。电化学实验结果表明:X70管线钢母材和焊缝在NS4溶液中的极化曲线都表现出典型的活性溶解特征,且有菌介质中管线钢表面能生成一层具有保护性的生物膜。SSRT曲线和SEM结果表明:在无菌NS4溶液中,X70钢母材和焊缝的SCC机理为氢致开裂机理。在有SRB的NS4溶液中,由于SRB生命代谢释放大量代谢产物H2S,促进H原子进入管线钢,将破坏其基体的连续性,从而导致氢损伤,使X70钢母材和焊缝的SCC敏感性都大于其在无菌介质中,其开裂机理表现为硫化物应力开裂和氢致开裂共同作用。在有菌和无菌介质中,焊缝的应力腐蚀敏感性均高于母材,这是由于焊缝处组织不均匀、存在残余应力造成的。
The stress corrosion cracking（ SCC） behavior of a welded X70 pipeline steel in the near-neutral p H solution with and without sulfate-reducing bacteria（ SRB） was studied by means of electrochemical potentiodynamic polarization curves,slow strain rate tension（ SSRT） and scanning electron microscopy. Electrochemical test results show that the polarization curves of the X70 pipeline steel and the welded joint in NS4 solution have typical characteristics of active dissolution,and the X70 steel surface can generate a protective layer of biofilm in NS4 solution with SRB. SSRT curves and SEM results show that the cracking generation mechanism of the X70 pipeline steel in NS4 solution without SRB is hydrogen induced cracking（ HIC）. In NS4 solution with SRB,a large amount of H2 S produced by SRB can facilitate the hydrogen permeation,leading to hydrogen damage. The SCC sensitivity of the base steel and the welded joint in the NS4 solution with SRB is greater than that in the NS4 solution without SRB. The mechanism of SCC of X70 steel is the combination of sulfide stress corrosion cracking（ SSCC） and HIC in the NS4 solution with SRB. Due to the inhomogeneous microstructure and residual stress generated in the welded joint,the SCC sensitivity of the X70 pipeline steel welded joint is greater than that of the base steel in the NS4 solution whether with or without SRB.
出处
《材料热处理学报》
EI
CAS
CSCD
北大核心
2016年第4期122-128,共7页
Transactions of Materials and Heat Treatment
基金
国家自然科学基金(51201009)
辽宁省自然科学基金(2013020078)
关键词
X70管线钢
焊缝
硫酸盐还原菌
慢应变速率拉伸
近中性pH溶液
应力腐蚀开裂
X70 pipeline steel
welded joint
sulfate reducing bacteria
slow strain rate tension
near-neutral PH solution
stress corrosion cracking
