Effect of trace elements on creep properties of 0.06C-2.25Cr-1.6W-0.1Mo-0.25V-0.05Nb steel

摘要

Effect of trace elements such as Mn and B on creep properties of 0.06C-2.25Cr-1.6W-0.1Mo-0.25V-0.05Nb have been investigated from the stand point of long term microstructural stability. With decreasing Mn-content, creep rupture strength has beenincreased due to reduction of minimum creep rate. The addition of B has also increased the life time due to delaying transition to tertiary creep. The creep strength is mainly controlled by the phase stability of fine dispersed carbides. Fine MC-typecarbides, which are stable at high temperatures, have contributed to delay of dislocation recovery. M{sub}23C{sub}6 and M{sub}7C{sub}3, however, have been transformed into coarse M{sub}6C with concentration of W during long term aging. Mn and B have beenfound to change the phase stability of M{sub}6C as well as M{sub}23C{sub}6 and M{sub}7C{sub}3. The transformation into M{sub}6C has been delayed with decreasing Mn-content and increasing B-content, which coincides with increasing creep strength.