Dependence of creep crack propagation on columnar grain orientation in cast HK40 tube

Abstract

Compact tension specimens having a columnar grain orientation inclined to the notch plane at an angle θ in the range 0–60° were prepared from a centrifugally cast HK40 tube. Constant load creep crack propagation tests were carried out on these specimens at 871°C. It wasfound that the creep cracks tended to advance along the columnar grain boundaries, and the crack propagation resistance increased with increasing θ. The dependence of creep crack propagation rate da/dt on the columnar grain orientation can be expressed as da/dt=A[K_Icos²(θ/2)]^m, where A and m are constants and K_I is the stress intensity factor. A good correlation between the creep crack propagation rate and the path independent integral C* confirms that the integral C* is an appropriate controlling factor for creep crack propagation in cast HK40 alloy.

MST/3244