Crack growth behaviour of a nickel-based powder metallurgy superalloy under elevated temperature

Crack growth behaviour of a nickel-based powder metallurgy superalloy has been studied under elevated temperatures. Test results show that there is a turning point for RT, 550 °C and 650 °C crack growth curves. Above this point, the three curves merge together and influence of elevated temperature disappears. Material characteristic microstructure length (grain size) is considered to be responsible for this phenomenon. However, this turning point is suppressed at 750 °C possibly by grain boundary weakening. Dwell tests show that effect of 90 s holding time on the crack growth rate is limited at 650 °C but much significant at 750 °C due to creep damage.