Today, newly developed 9% Cr-steels, such as T/P911 and T/P92, are used for power
plants with advanced steam parameters, thanks to their high creep rupture strength
values. They show an increase of creep values by around 10 to 25 %, compared with T/P91.
Nevertheless, their range of use is limited for high temperature because their oxidation
resistance is lower than that of the classical 12%Cr-steels, such as X20CrMoV12-1 or
the austenitic steels. In order to meet higher design parameters, a new steel, named VM12,
has been developed by Vallourec and Mannesmann Tubes (V&M). The aim was to keep the high
creep level of the T/P92 together with improvement of the steam oxidation resistance
to fit with design steam temperature up to 650°C.