THE ELEVATED TEMPERATURE PROPERTIES OF TYPE 301 EFH STAINLESS STEEL, TI-5AL-2.5SN AND TI-13V-11CR-3AL ALLOYS UNDER STEADY STATE AND CYCLIC CREEP CONDITIONS

The elevated temperature creep properties of Type 301 EFH Stainless Steel and two titanium alloys, Ti-5Al-2.5Sn and Ti-13V-11Cr-3Al were evaluated at 600F and 900F under steady state, cyclic load and cyclic temperature creep exposure. In addition the effects of creep strain on subsequent room temperature tensile properties were studied. On the basis of density compensated tensile and creep strength, the Ti-13V-11Cr-3Al alloy (B120VCA) was found to be the best alloy for use from room temperature to about 800F. Above 800F the Ti-5Al-2.5Sn alloy (A110AT) is the better material. Between 400F and 800F the 301 EFH and Ti-5Al-2.5Sn alloys are quite competitive when compared on a density compensated basis. On an over-all basis the stainless steel appears slightly superior in this temperature range. Below 400F the Ti-5Al-2.5Sn alloy may be the better choice. The effects of cyclic loading and cyclic temperature creep exposure compared to steady state creep exposure on the over-all creep strain and creep rate was quite small in general. Creep damage, i.e., the decrease in room temperature tensile properties due to prior exposure to stress at elevated temperatures, was quite small also except for elongation. In general, changes in F sub tu and F sub ty did not exceed 6 percent. Decreases in ductivity due to creep damage were quite large in some cases. For example, the elongation of the Ti-5Al-2.5Sn alloy decreased from 22 percent to about 7 percent when stressed for periods of 24 hours at 900F. Creep damage produced by cycle creep conditions was similar to that found under steady state creep conditions. (Author)