AbstractCompact tension specimens having a columnar grain orientation inclined to the notch plane at an angleθin 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 increasingθ. The dependence of creep crack propagation rate da/dt on the columnar grain orientation can be expressed as da/dt=A[KIcos2(θ/2)]m, where A and m are constants and KIis 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