Abstract
The corrosion properties of Fe-Cr-Mn-C-N high interstitial austenitic stainless cast steels were investigated for down-hole application in sour environments. The two cast alloys contained 0.66% and 0.71% of total nitrogen and carbon. The corrosion properties of the alloys that were solution-treated and fast-cooled were directly responsible for high corrosion resistance in NaCl solution, including resistance to pitting corrosion resulting from a better distribution of chromium chemical compound in the high interstitial stainless cast steel. However, the sour corrosion resistance of the alloys decreased with the fast cooling rate, which can be attributed to the increased amount of ferrite containing Fe2+, which causes iron sulfide precipitate formation in H2S.
Highlights
Serious corrosion is encountered in sour gas wells and reservoirs during the extraction of oil and gas
The corrosion properties of the developed alloys were investigated according to different conditions, such as solution treatment (1473.15 K for 2 h), different cooling rate (air (>1 K/s), water (>130 K/s)), and carbon and nitrogen content (0.66 wt.%/CN66, 0.71 wt.%/CN71)
High interstitial austenitic alloys and a stainless steel 316L, a benchmark alloy, it concluded that the benchmark alloy showed the highest corrosion rate (1 mpy), compared with high interstitial stainless steels
Summary
Serious corrosion is encountered in sour gas wells and reservoirs during the extraction of oil and gas. In order to ensure safety and the long-term development of gas wells, materials with superior corrosion resistance are required for well-production systems [1]. Austenitic stainless cast steels are widely used for the development of gas wells in the sour environment due to their superior mechanical performance. Nickel-based austenitic stainless cast steels are the most common. These austenitic stainless cast steels have a corrosion resistance when they form a passivation layer of chromium (III) oxide (Cr2 O3 ) to prevent oxidation. Degradation in corrosion resistance due to undesirable phases, such as the formation of various chemical compounds (chromium carbides and nitrides) in the steel, is a typical problem for down-hole applications [2,3]. The deleterious effects of the precipitation as either chromium carbide or nitride on pitting corrosion, with the formation of a chromium depletion zone adjacent to those compounds, have been reported and sensitization has occurred as a result [4]
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