A three-dimensional characterization of creep void formation in hydrogen reformer tubes

The techniques of serial sectioning and three-dimensional reconstruction were used to characterize creep voids occurring in an ex-service hydrogen reformer tube. The influence of variations in temperature, stress and microstructure types on the characteristics of creep voids are considered in the study. The results revealed that the highest void density per grain boundary area occurred at the outer wall of the tube where the temperature is highest and the microstructure consists of large columnar grains, compared to the inner wall of the tube consisting of smaller equiaxed grains.