Assessment of creep crack growth in dissimilar metal welds

Experimental and analytical work is described which extends existing creep crack growth estimation methods based on the creep fracture mechanics parameter C* to interfacial crack growth in dissimilar metal welds (DMW) between austenitic and ferritic steels. Creep crack growth tests on DMW test specimens with an Inconel filler are reported and the results presented in terms of measured crack growth rate d a/d t versus experimentally determined C*. The data are compared with homogeneous specimen data on the ferritic material and shown to lie below the ferritic upper-bound line. Similar data for a DMW with an austenitic filler are referenced. Finite element bi-material calculations of the compact tension test specimens are also described under both load and displacement control. It is shown that the results of this work support a simple approach to assessing creep crack growth in DMW based on homogeneous approximations.