The realization of advanced thermal power plants with increased efficiencies requires the development of new materials with enhanced capabilities in respect to high temperature strength and steam oxidation behavior. The change in the environmental policy and the increasing contribution of renewable energy sources into the public electric grid has changed the operation mode of the existing power plants in Europe. Instead of quasi stationary operation, for which the conventional thermal power plant fleet was designed, cyclic operation modes will dominate the power plant service lifetime. The creep-fatigue phenomena, however, may be responsible for significant lifetime reductions compared with the original design lifetime. Revamping of the existing power plants by application of “stronger” materials with improved steam-oxidation behavior, allowing wall thickness reduction can be a possible way to address the topic. Recently, Vallourec developed a new high-Cr ferritic-martensitic steel that combines excellent creep rupture strength properties and enhanced steam oxidation resistance of 12%Cr steels such as VM12-SHC or X20CrMoV11-1. Industrial products were successfully manufactured and the creep and steam oxidation properties were validated.

A new modified 9 wt% Cr steel has been developed in order to improve the resistance against coke deposition on the internal surface of refinery tube furnaces, in comparison to widely used grades, such as Grade 5 (5 wt% Cr) or Grade 9 (9 wt% Cr). The new grade has an improved composition, based on Cr and Si and further additions of Cu and Ni. This optimal chemical analysis has been specified after extensive laboratory testing on different laboratory and industrial heats. Thermogravimetric analyses have been performed to benchmark various materials (ferritic and austenitic grades) in terms of coking rate. Specimens of these alloys have been exposed to this coking atmosphere in a wide temperature range. The new modified 9Cr steel exhibits an almost 10 times lower coking rates than typical Grade 9 steel. The new 9Cr steel shows allowable stress levels up to 90% higher than Grade 9 at temperatures below 500°C (time independent regime) and up to 7% higher stress levels at temperatures above 500°C (creep regime). The industrial feasibility of production of elbows has been successfully implemented and a welding solution using a commercially available filler material has been established.