Influence of specimen thickness on the creep behavior of a directional solidification nickel-based superalloy

The effects of thickness and surface signature on the creep life of a directionally solidified nickel based superalloy were investigated. The creep tests of ground specimens in the thickness of 0.61 mm and 0.89 mm, as well as polished ones with 0.66 mm and 0.87 mm in thickness were performed at 980 °C/160 MPa. Based on the experimental results, the thin ones had inferior creep life compared with thick specimens. XRD exhibited that all the specimens were oxidized during the creep tests, however, the non-loading bear zones which caused by oxidation was insufficient to explain the creep life of specimens under different wall thicknesses. On the other hand, the morphology of fracture sections indicated that the interaction of cracks and creep damage could reveal this phenomena. It worth noting that the cracks played a more important role in the creeping of thin specimens, but creep damage influenced the thick specimens more effectly. In addition, the polished specimens had a better behavior during creep tests than the ground ones.