Creep rates and strengthening mechanisms in tungsten-strengthened 9Cr steels

The creep deformation behavior has been investigated for simple 9Cr–W and solute modified 9Cr–WVTa steels containing high W, where Fe2W Laves phase precipitates during creep. Creep tests were carried out at 823, 873 and 923 K for up to 15 000 h. The precipitation of Fe2W effectively decreases a minimum creep rate, but the large coarsening of Fe2W promotes the acceleration of creep rate after reaching a minimum creep rate. As a result, the effect of Fe2W on the extension of creep rupture time is rather small. The fine MC carbides are significantly effective for the stabilization of lath martensitic microstructure.