Question

A superalloy gas turbine component was originally designed to operate at temperatures up to 760°C and exhibited a stress rupture life of 900 hr. under this operating condition. An updated design calls for a thermal barrier coating (TBC) to be added to the same component to allow engine operation under the same conditions, but with an increase in reliability. If an increase in rupture life to 1800 hr. is desired, what temperature difference between the inside and outside of the component must be achieved by the addition of the TBC?

Answer 1

in this problem the value of larson millars constant should be given

since it not mentioned i have taken it as 20 which is general value

Tia 760c 7 760 +273 ) 1033 T2 = ? L =) 900 hr Iz zs 1800 h By Larson miller parameter Lmpz T (C+ lg 1) (y Larson's millor Constant Let say (assume) (= 20 sin Lup remains Constant To (C+ log L.) 1033 (20+ log (900)) = Tz (zot lag 1800) 23711173 Tz ( 23.2552) = Tz (Ct log L2) T2 = 1019.63 or 746.63 °C difference in temperature 760-746 (140 In this problem I assumed C = 20 *