Creep-damaged pipe steels probed with positron spectroscopy

Using positron lifetime spectroscopy (POLIS) the degree of damage in creep-influenced pipe steels was found to decrease with depth, as measured from the physical surface of the samples. Ultrasonic measurements were revealed to mostly note the differences in internal stresses, not in the microstructure. A critical limit of 160 ps average positron lifetime was determined at about 80% of material lifetime consumption in a creep experiment, independent of the material or the creep test parameters. The results suggest the technique of positron lifetime spectroscopy as a method for nondestructive monitoring of creep damage