The creep strength of martensitic 9% chromium steels is strongly coupled with the formation and interaction of different precipitate populations like MX (Nb,V)(C,N), M23C6, laves phase and modified Z-phase. Changes in microstructure can be correlated to a change in creep strength. Within this work, a boron-nitrogen balanced 9Cr3W3CoVNb steel is investigated in normalised and tempered (as-received), creep exposed and welded condition. Microstructural characterisation of as-received and creep exposed samples have been carried out by elemental mapping techniques in transmission electron microscopy. The creep strength of the base material has been evaluated at 650°C up to a current testing duration of 24,000 hours. Comparison of creep rupture strength after 20,000 hours shows a benefit in strength of the new grade of about 25 MPa compared to conventional steel grade P92 and 45 MPa to grade P91. The results of the microstructural investigation show only very little changes of the initial microstructure after 10,000 h of creep exposure. The investigations imply a higher microstructural stability of the new steel, compared to other 9% chromium steel grades.In welded condition, the steel shows unique formation of its heat-affected zone. Although the steel experiences several phase transformations during the weld thermal cycle, the original base material grain structure is almost completely retained in the heat-affected zone. The formation of a homogeneous grain refined region is suppressed and, therefore, less susceptibility to Type IV cracking is expected. Creep tests of crossweld specimens at 650°C and various stress levels show similar creep strength to grade P91 base material.