Effect Of Shot Peening And Post-peeningheat Treatments On The Microstructure, Theresidual Stresses And Hardness, Corrosionand Deuterium Uptake Resistance OfZr-2.5Nb Pressure Tube Material

Abstract

The effect of shot peening and post-peening heat treatment on the microstructure, the residual stresses, hardness, corrosion and deuterium uptake behaviour of Zr-2.5Nb pressure tube material has been evaluated. Shot peening produced a heavily cold-worked microstructure, with the original grain structure completely obliterated by the shot-peening process. Shot peening also caused a change in the texture of this material. Heat treating shotpeened specimens at temperatures from 670 to 770 K caused recrystallization of the cold-worked surface layers and breakup of the grain-boundary 0-phase network. The recrystallization is accompanied by precipitation within the a-Zr grains of fine uniformly distributed Nb-rich 0-phase particles and the reduction in the Nb supersaturation of the a-Zr phase from =1.5 to =0.5 at.% Nb. Shot peening produced an improvement in the corrosion and deuterium uptake resistance of Zr-2.5Nb pressure tube material. The improved corrosion and deuterium uptake resistance was attributed to the intense cold work and to microstructural changes produced by shot peening and post-peening heat treatments.