• PDF / 6,251,744 Bytes
• 12 Pages / 593.972 x 792 pts Page_size
• 6 Downloads / 247 Views

DOWNLOAD

REPORT

---

INTRODUCTION

AS the oil industry develops rapidly, an increasing number of oil-gas fields are being exploited. These fields usually contain high concentrations of H2S and CO2, which can cause stress corrosion cracking (SCC) of metal components, especially pipelines. In recent years, SCC has caused several serious accidents, threatening the safe operation of oil-gas fields.[1,2] Austenitic stainless steel is widely used in modern oil-gas fields given its good corrosion resistance and formability. However, this material suffers from low hardness and poor wear resistance, limiting its usage in acidic environments in which abrasion and corrosion occur.[3,4] SCC is one of the most common failure modes in oil-gas fields. A related failure mechanism in H2S-CO2 environments has been studied extensively,[5–7] and

XIANGFENG ZHANG, JUN WANG, HONGYUAN FAN, LIAN DUAN, GUANG XIAN, and LAN SUN are with the School of Manufacturing Science and Engineering, Sichuan University, Chengdu, Sichuan 610065, China. Contact email: [email protected] JING YAN and TAN GU are with the Natural Gas Research Institute of Southwest Oil & Gasfield Company, PetroChina, Chengdu, Sichuan 610213, China. DANQI WANG is with the Swagelok Center for Surface Analysis of Materials, Case Western Reserve University, 10900 Euclid Ave, Cleveland, OH 44106. Manuscript submitted May 4, 2017.

METALLURGICAL AND MATERIALS TRANSACTIONS A

significant progress has been made in the areas of corrosion behavior and mechanism, material selection, and failure prevention. Lauvstad et al. examined the effects of H2S and Cl on the pitting initiation of 316L austenitic stainless steel.[8] They proposed that oxidation of sulfide constitutes an extra anodic reaction in the passive potential range, significantly increasing the transportation of electrons through the oxide. SCC has also been attributed to hydrogen embrittlement induced by the formation of metallic sulfides from H2S.[9,10] In a corrosive medium, H2S reacts with the metal, producing metallic sulfides on the surface whilst simultaneously releasing hydrogen atoms, which can be absorbed on the metal surface and induce embrittlement.[11] A mechanism proceeding via iron sulfide formation based on the adsorption and reduction of H2S has also been proposed. An H2S-CO2-Cl environment is highly corrosive to metals, especially in wet H2S environments.[12,13] It was found that once H2S dissolves in water, it immediately ionizes and acidifies the solution, accelerating the corrosion rate and damaging the pipeline easily in combination with stress.[14] Low-temperature liquid nitridation technology is a new, green surface treatment, which requires less extensive equipment setup and involves a simpler process compared to other surface treatment techniques.[15] Low-temperature liquid nitridation is particularly effective on components with complex structures due to the

uniformity of the nitriding medium.[16] 316 Austenitic stainless steel is an ideal candidate to prevent or mitigate SCC of pipelines in deep, sour oil-gas fields. It has been es