MarBN steels, originally developed by Professor Fujio Abe at NIMS Japan, have undergone significant advancement in the UK through a series of government-funded collaborative projects (IMPACT, IMPEL, INMAP, IMPULSE, and IMPLANT). These initiatives have achieved several major milestones, including operational power plant trials, full-scale extruded pipe production, matching welding consumable development, and most notably, the creation of IBN-1—a new steel demonstrating 30-45% higher creep strength than Grade 92. However, like other creep strength-enhanced ferritic steels, IBN-1 shows reduced creep ductility under the lower stress conditions typical of operational use. Since adequate creep ductility is essential for component damage tolerance and effective in-service monitoring, this study investigates the effects of an alternative normalizing and tempering heat treatment on cast IBN-1. The research presents creep rupture test results showing improved ductility and analyzes the microstructural mechanisms responsible for this enhancement.

To meet worldwide emission targets many Government policies either avoid the use of coal burning plant for future energy production, or restrict emissions per kilogram of coal consumed beyond the capability of most conventional plant. As a result this has accelerated current worldwide developments of steel and nickel alloys for coal-fired plant to operate at temperatures in excess of 625°C. Within the UK a modified 9%Cr steel has been developed which is based on the MarBN steel first proposed by Professor Fujio Abe of NIMS Japan, and has been designated IBN-1. The steel is modified by additions of, typically, 3% cobalt and tungsten with controlled additions of boron and nitrogen. While development of 9%Cr steels has continued since the last EPRI high temperature material conference in 2016 (Portugal), parallel developments in nickel alloy castings for even higher temperature and pressure applications have also continued. This paper summarises the latest developments in both of these material types.