Development of High Interstitial Stainless Steel and Evaluation of Its NaCl Corrosion Resistance
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Development of High Interstitial Stainless Steel and Evaluation of Its NaCl Corrosion Resistance Cheolmin Ahn1 · Hyunju Lee2 · Yoonseok Lee3 · Seungchan Cho4 · Brajendra Mishra5 · Eunkyung Lee1 Received: 14 August 2019 / Accepted: 14 October 2019 © The Korean Institute of Metals and Materials 2019
Abstract High interstitial Fe–Cr–Mn–C–N stainless steels, CN66 (0.38 wt% N + 0.28 wt% C) and CN71 (0.44 wt% N + 0.27 wt% C), were cast under atmospheric pressure to develop a new drill collar for use in petroleum industry. To evaluate the corrosion property, CN66 and CN71 were compared with high-Mn stainless steel, P550, which is currently being used as a drill collar material. Through the measurement of the corrosion resistance based on the chemical compositions, CN71 exhibited the highest corrosion property, a mean of 35.74, corresponding to strong corrosion resistance. However, CN71 exhibited a mean of 0.517 mpy for the corrosion rate compared to 0.37 mpy for P550, after the immersion experiment in 3.5 wt% NaCl. With high C content, the formation of carbide along the grain boundaries in CN71 and CN66 caused intergranular corrosion. However, this could be restricted by heat treatment at 1050 °C and 1180 °C with uniform distributions of chemical compositions via air cooling, decreasing the corrosion rates significantly. Keywords High interstitial stainless steel · Corrosion resistance · Microstructure · Heat treatment
1 Introduction Recently, petroleum processing under severe conditions, such as deep and high-pressure sour gas wells, has been conducted inevitably owing to its rapid consumption as an energy source. To efficiently collect the gas under the deep
* Eunkyung Lee [email protected] Brajendra Mishra [email protected] 1
Department of Ocean Advanced Materials Convergence Engineering, Korea Maritime and Ocean University, Busan 49112, Republic of Korea
2
Mineral Resources Research Division, Korea Institute of Geoscience and Mineral Resources, Daejeon 34132, Republic of Korea
3
Graduate School of Natural Science and Technology, Okayama University, 3‑1‑1 Tsushima‑naka Kita‑ku, Okayama, Japan
4
Functional Composites Department, Korea Institute of Materials Science (KIMS), Changwon 51508, Republic of Korea
5
Metal Processing Institute, Worcester Polytechnic Institute, Worcester, MA 01609, USA
conditions, drill bits are used in the process. To enhance productivity, a drill collar can be used on the drill bit. Although the parts of the drill bit benefit petroleum processing, they are easily exposed to a sour environment, which causes detrimental abrasion and corrosion. These severe conditions include exposure to large amounts of hydrogen sulfide ( H2S) and carbon dioxide (CO2), which result in electrochemical corrosion of the material [1]. Therefore, new materials with superior corrosion resistance are required to avoid deleterious corrosion under sour gas well, which is harmful to the life of materials [2]. Therefore, high-corrosion-resistant materials such as stainless steels have been applie
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