Influence of Y-Rich Compounds on High-Cycle Fatigue Performance of Y-Doped M951 Superalloy
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The performance of Y-doped M951 superalloy under high-cycle fatigue was investigated experimentally to determine the effect of Y-rich compounds on this behavior. The selected testing temperatures were 700 and 900 °C, and the stress ratio was R = 0.1. The fatigue life was shown to decrease as the stress amplitude increased, according to a typical Whöler S-N diagram. Two types of crack initiation sites were observed on the fractured surfaces: microshrinkage clusters and Y-rich compounds. Analysis by TEM indicated that the Y-rich compounds consisted of Al2Ni6Y3 particles with BCC structure and Ni5Y particles with hexagonal structure. Cracks had initiated and propagated along the interface between Al2Ni6Y3 phase and the matrix. These Y-rich compounds varied considerably in size, from 1 to 769 μm, and the large-size Y-rich compounds were shown to be the preferred site for fatigue crack origin. The ability of Y in the removal of sulfur was considered. And the small-size Y-S product from the reaction between Y and S was shown to exhibit no deleterious effect on the fatigue property of the M951 Ni-based superalloy.
Keywordscasting and solidification failure analysis high-cycle fatigue superalloys yttrium
This research was financially supported by the National Natural Science Foundation of China, No. 51471079, and Jiangsu Natural Science Foundation, BK20130464. The authors are also grateful for the financial support from the Jiangsu Government Scholarship for Oversea Studies.
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