R-TECH Group received two lengths of tube from a boiler economiser tube from a power station. One of the samples had developed a leak. R-TECH Group were requested to determine the cause of the rupture.
Dye penetrant testing (DPI) was undertaken, but no defects were detected other than the perforation shown in Figure 2. A section was taken through the area of the perforation, and etched for metallographic preparation. This showed that the cracking initiated in the Heat Affected Zone (HAZ) of the butt weld (see Figure 3). There were no material defects associated with the cracking.
Sections taken away from the perforation showed the presence of numerous straight cracks all containing oxide (see Figures 4 and 5). These cracks are characteristic of thermal fatigue, and this was identified as the failure mechanism in this case.
A thorough failure analysis investigation is a valuable and informative tool to reduce the likelihood of a repeat incident which improves safety and productivity and can enable evolution towards a better product. If you would like to know more about our Failure Analysis services, please contact us.
Accurate testing, trusted insight, and practical solutions to help you make confident decisions where materials matter most.
