Delayed hydride cracking in Zr–2.5Nb pressure tube material: influence of fabrication routes

The delayed hydride cracking (DHC) velocity was measured for Zr–2.5Nb alloy pressure tubes manufactured from cold-worked and stress-relieved (CWSR) route and quenched and aged (Q&A) route at 162, 203, and 250 °C. It was observed that the DHC velocity in the pressure tubes produced from Q&A route is about half to one-third of that observed in the tubes produced from CWSR route. The lower DHC velocity in Q&A tubes compared to that in the CWSR tubes have been rationalized in terms of the difference in strength and effective hydrogen diffusivity compared to the tubes manufactured from CWSR route. A modification to Dutton–Puls model of DHC is suggested by proposing alternate expression for the elastic stress-field ahead of a sharp crack for an elasto-plastic material.