Effect of manufacturing route on thermal creep behaviour of Zr-2.5Nb pressure tube alloy used in Indian PHWR

•The present study compares the thermal creep behaviour of different generations of the Zr-2.5Nb pressure tube used in Indian Pressurized Heavy Water Reactors.•Pressure tubes manufactured from new route were found to be more creep resistant than the tubes manufactured from old route.•Both grain size and aspect ratio of the new route tubes were higher than that of old route tubes.•Higher extrusion ratios incorporated in fabrication of new route tubes produced stronger texture, which resulted in better creep properties.•Stress exponent and activation energy values revealed that the creep deformation mechanism was dislocation creep mechanism (dislocation climb – rate controlling mechanism, dislocation glide – strain producing mechanism).