Creep behavior of oxide dispersion strengthened 8Cr-2WVTa and 8Cr-1W steels

Microstructures and creep behavior of two martensitic oxide dispersion strengthened (ODS) steels 8%Cr-2%W-0.2%V-0.1%Ta J1) and 8%Cr-1%W (J2) with finely dispersed Y2Ti2O7 have been investigated. Creep tests have been carried out at 670, 700 and 730 degrees C. Creep strength of J1 is stronger than that of any other ODS martensitic steels and the hoop strength of the ferritic ODS steel cladding. At the beginning of creep test, shrinkage was frequently observed for J1. This is one of the reasons for high creep strength of J1. The delta-ferrite, which is untransformed to austenite at hot isostatic press and hot rolling temperatures, was elongated along the rolling direction, and volume fraction of delta-ferrite in J1 is larger than J2. Although the elongated delta-ferrite affects the anisotropy of creep behavior, the extent of anisotropy in J1 is not so large as that of the ferritic ODS steel. (C) 2008 Elsevier B.V. All rights reserved.