Creep crack growth verification testing in tubular components

A method is described for determining the creep crack growth (CCG) and stress rupture behavior of Alloy 800H tubular components containing longitudinal surface defects at 800 degrees C. The presence of the notch is found to systematically reduce the stress to rupture over a wide stress range. Creep crack growth rates derived from potential drop measurements across the notch show consistent KI and C* dependence. Comparison with creep crack growth behavior from conventional specimens confirms that C* is the most appropriate correlation factor. Finally, attention is drawn to the potential dangers of predicting component CCG behavior from conventional specimen data for structure sensitive materials such as Alloy 800H and conversely to the potential advantage of the component type CCG tests developed in the present work