Pitting Corrosion Resistance affecting Corrosion Fatigue Behavior of CrMn-stainless steel in Chloride-containing Solutions

摘要

Cyclical mechanical stresses in combination with corrosive environments significantly affect the integrity of austenitic CrMn-stainless steels that are typically used as structural materials in drillstring components. Consequently, environmental assisted cracking is one of the most frequent causes of tool failure during drilling operations. From practical experience it has been observed that environmental-assisted cracks start in many cases from pits formed at the material surface and propagate by the combined effect of the drilling-related loads and the drilling environment. Localized corrosion resistance of CrMn-stainless steels depends on environmental factors such as chloride concentration, alkalinity and temperature. As application temperatures increase the susceptibility to localized corrosion of CrMn-stainless steels increases, therefore, a good understanding on the relationship between localized corrosion resistance and environmental assisted cracking susceptibility is critical for material selection. The present paper discusses the synergistic effect of pitting corrosion and corrosion fatigue resistance on CrMn-stainless steel observed after electrochemical and corrosion fatigue tests were conducted in simulated drilling environments at different temperatures.