Static creep crack growth tests and displacement controlled fatigue and creep-fatigue crack growth tests have been performed on austenitic feature weld specimens at 650°C. The creep-fatigue tests incorporated hold times of up to 96 h. During these tests, crack growth appeared to comprise cyclic and dwell components. Cyclic crack growth components were characterised by the fracture mechanics parameter K whilst creep crack growth contributions were correlated with C * . In order to determine K and C* for the non-standard feature weld specimen, elastic and elastic-plastic creep finite element analyses were conducted. Good correspondence is shown between the feature weld data and comparable data from compact tension specimen tests on similar materials. Equations obtained from the compact tension specimen results, which describe total crack growth rates as the sum of the cyclic and dwell contributions, are shown to adequately describe the features test results also. Furthermore, it is demonstrated that a reference stress approach can be used to estimate C* for the features specimens. NOMENCLATURE da/dN = crack growth rate (da /dN), = hold period contribution to crack growth rate during creep-fatigue test (da/dN), = cyclic contribution to crack growth rate during creep-fatigue test a = crack length B =thickness of compact tension specimen C* = creep crack growth correlating parameter E = Young's modulus J = non-linear elastic fracture mechanics parameter K = stress intensity factor ,f'(a/W) = C* calibration AKeK= stress intensity factor range for which cracks are open AK,,, =total stress intensity factor range P = load q, = ratio of load range for which cracks are open to total load range R = ratio of minimum load in cycle to maximum in cycle t = time t,, = hold period duration W =width of specimen Y = compliance function i = creep rate A P = load range = load line displacement rate during creep crack growth u , , = reference stress 187 188 D. N. GLADWIN et al.