1 School of Metallurgy, Northeastern University, Shenyang 110819, Liaoning, China; 2 State Key Laboratory of Metal Material for Marine Equipment and Application, Anshan 114002, Liaoning, China
Effects of nitrogen content on pitting corrosion resistance of non-magnetic drill collar steel
1 School of Metallurgy, Northeastern University, Shenyang 110819, Liaoning, China; 2 State Key Laboratory of Metal Material for Marine Equipment and Application, Anshan 114002, Liaoning, China
摘要 High-nitrogen (N) austenitic stainless steel (Cr–Mn–N series) is commonly used for non-magnetic drill collars, which exhibits excellent mechanical properties and corrosion resistance. The effects of N content (0.63 to 0.86 wt.%) on the pitting corrosion behavior of the experimental non-magnetic drill collar steel were investigated using the electrochemical tests and immersion tests. Besides, X-ray photoelectron spectroscopy was used to analyze the constitution of the passive film. The results show that with the enhancement of N content from 0.63 to 0.86 wt.%, the metastable pitting corrosion sensitivity of the tested materials in 3.5 wt.% NaCl solution decreased and the pitting corrosion resistance increased. Meanwhile, the corrosion rate in 6 wt.% FeCl3 solution at 30 °C decreased from 10.40 to 4.93 mm/a. On the other hand, nitrogen was concentrated in the form of ammonia (NH4+ and NH3) on the outermost surface of the passive films. The contents of Cr2O3 and Fe2O3 raised in the passive films, together with the content of CrN, at metal/film interface increased as N content increased from 0.63 to 0.86 wt.%, which facilitated protective ability of the passive films, thus contributing to higher pitting corrosion resistance.
Abstract：High-nitrogen (N) austenitic stainless steel (Cr–Mn–N series) is commonly used for non-magnetic drill collars, which exhibits excellent mechanical properties and corrosion resistance. The effects of N content (0.63 to 0.86 wt.%) on the pitting corrosion behavior of the experimental non-magnetic drill collar steel were investigated using the electrochemical tests and immersion tests. Besides, X-ray photoelectron spectroscopy was used to analyze the constitution of the passive film. The results show that with the enhancement of N content from 0.63 to 0.86 wt.%, the metastable pitting corrosion sensitivity of the tested materials in 3.5 wt.% NaCl solution decreased and the pitting corrosion resistance increased. Meanwhile, the corrosion rate in 6 wt.% FeCl3 solution at 30 °C decreased from 10.40 to 4.93 mm/a. On the other hand, nitrogen was concentrated in the form of ammonia (NH4+ and NH3) on the outermost surface of the passive films. The contents of Cr2O3 and Fe2O3 raised in the passive films, together with the content of CrN, at metal/film interface increased as N content increased from 0.63 to 0.86 wt.%, which facilitated protective ability of the passive films, thus contributing to higher pitting corrosion resistance.
Li‑wei Xu,Hua‑bing Li,Huai‑bei Zheng, et al. Effects of nitrogen content on pitting corrosion resistance of non-magnetic drill collar steel[J]. Journal of Iron and Steel Research International, 2020, 27(12): 1466-1475.
2020, Vol. 27 
