Centrifugally cast 25 Cr superduplex solid corrosion resistant alloy (CRA) pipe for upstream oil and gas

摘要

Centrifugal casting is a process which allows for the manufacture of seamless pipes of various solid corrosion resistant alloys. This foundry process offers flexibility in terms of ability to produce different dimensions as well as offers advantage over static casting in the realization of key material properties. In this contribution the results obtained from a 25% Cr superduplex alloy are reported in terms of the mechanical properties, microstructural features as well as the corrosion properties. Microstructural studies on the as-cast state reveal that the addition of copper as an alloying element in the superduplex alloy leads to a refinement in the microstructure during solid state transformation of the ferrite to austenite. The presence of fine austenite leads to attainment of microstructures without intragranular chromium nitrides during the subsequent quenching step after solution-annealing. Additionally, the properties of this alloy in the solution annealed condition meet the minimum material requirements necessary as per industry standards for the wrought superduplex alloy grades used for line pipe applications in the oil and gas industry. Centrifugally cast super duplex pipe is a viable alternative for wrought seamless superduplex pipes.