Influence of surface recrystallization on the low cycle fatigue behaviour of a single crystal superalloy

ABSTRACT This paper investigated the effect of surface recrystallization (RX) on the low cycle fatigue (LCF) behaviour of a single crystal (SX) superalloy. LCF tests on both raw and recrystallized samples showed that fatigue life was significantly reduced by surface RX. Fractography indicated that f...

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Bibliographic Details
Published in:Fatigue & fracture of engineering materials & structures 2015-03, Vol.38 (3), p.340-351
Main Authors: Ma, X., Shi, H.-J., Gu, J., Yang, Z., Chen, G., Luesebrink, O., Harders, H.
Format: Article
Language:English
Subjects:
Alloys
Crack initiation
Crack propagation
low cycle fatigue
Metal fatigue
Recrystallization
single crystal superalloy
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Summary:ABSTRACT This paper investigated the effect of surface recrystallization (RX) on the low cycle fatigue (LCF) behaviour of a single crystal (SX) superalloy. LCF tests on both raw and recrystallized samples showed that fatigue life was significantly reduced by surface RX. Fractography indicated that fatigue cracks initiated from the casting defects in RX layer and multiple crack initiations were commonly observed. Moreover, RX grains exhibited predominantly transgranular cracking, in contrast to the intergranular fracture reported in literature. The fatigue crack propagation behaviour was discussed in light of fracture mechanics and crack growth life model. The fatigue cycles required to penetrate RX layer were estimated to be about one magnitude lower than that in forming an equivalent crack in SX specimens. It is suggested that the earlier crack initiation and promoted crack propagation in RX layer, as well as the trend of multiple initiations, are responsible for the fatigue degradation by RX.
ISSN:8756-758X
1460-2695
DOI:10.1111/ffe.12236