| The object of this study is to characterize the high temperature properties and the effect of aging treatment on mechanical properties in modified Fe-15Cr-26Ni-1.25Mo type precipitation hardening alloy containing Ti content of 1.1-1.3 wt%. It has been investigated mainly by tensile test, micro-vickers hardness test, scanning electron microscopy EDAX, charpy n-notch impact, low cycle fatigue, and combination smooth-notch stress-rupture test. The results obtained are summerized as follows; For modified Fe-15Cr-26Ni-1.25Mo type precipitation hardening alloy The optimum heat treatment condition are selected. It is clarified that an optimum Ti content of 1.1-1.3% meets the required mechanical properties of ultra supercritical steam turbine at 649℃. The charpy absorbed energy was almost stable at 13㎏-m∼12㎏-m from R.T to -140℃ The failure cycles(N_f) are 13,022 in Δε_t(%)=0.5 and 1,254 in Δε_t(%)=1 at 650℃. It appers lower notch sensitivity in combination smooth-notch stress-rupture test at 650℃, judging from not fractured at notched part but at smooth part. |
|
