Abstract
The good mechanical properties as well as the large range of corrosion resistance justify the use of super martensitics in oil and gas production fields. Nevertheless with UNS 17400, which is largely used, some in-service failures have occurred. In this context, the super martensitic stainless steel 15Cr5Ni0.8Mo, which has good mechanical and corrosion properties, could be a good candidate to replace it.
In this work, different alloying elements are studied with laboratory heats to optimize its chemical composition for oil & gas application. The control of microstructure eliminates residual ferrite and retained austenite as parameters in corrosion behavior. The positive influence of buffer test solution is described and the reinforcement of passive film in non sour medium is explained. Then the influence of H2S on passive film and corrosion mechanism is highlighted, in particular when the gas destabilizes a passive film allowing generalized corrosion. Influence of alloying elements is related to the corrosion mechanism: a positive effect of chromium, molybdenum and copper is observed on corrosion resistance in sulfur medium. The effect of molybdenum on SSC resistance is described.
