N80钢C-N-O-S共渗层组织和耐蚀性研究

采用低温气体多元共渗技术在N80钢表面获得了C-N-O-S共渗层;采用XRD测试了共渗层的相组成;利用SEM、EDX观察了渗层形貌、厚度及共渗元素的分布;在含饱和CO2的模拟油田介质中测试了共渗层的极化曲线与渗层的腐蚀速率。试验结果表明,渗层厚约50μm,主相为高电位的Fe4N、FeS,并在表面层含有Fe2O3和Fe3O4,氮化物按纵-横-纵的方式分布,C-N-O-S共渗层自腐蚀电位正移300 mV,在120℃腐蚀失重从空白试样的2.11 g/(m2.h)下降为0.62 g/(m2.h)。

Analysis on Microstructure and Corrosion Resistance of C-N-O-S Penetrated Layer on N80 Steel

Using low temperature gas multi-component infiltration technique, C N-O-S penetrated layer was obtained on the samples of N80 steel. The phase composition and microstructure of alloying layer were investigated by XRD, SEM and EDX. Corrosion behavior of penetrated layer in simulated brine being saturated with carbon dioxide was investigated using high temperature high pressure autoclave and electrochemical method. The results show that the thickness of C-N-O-S penetrated layer is about 50ttm, the primary phase contains high potential Fe4N, FeS, and the less of Fea04 and Fe2 03 is on the surface of C-N-O-S penetrated layer. The high potential of nitrogen distributes with vertical-horizontal-vertical on the surface of N80 steel. Compared with the substrate, the corrosion potential of C-N-O-S penetrated layer increases 300 mV in positive direction, the rate of weight Loss decreases from2.11 g/（m^2·h） to 0.62g/（m^2 · h） when T=120℃.