Effects of microstructures on fatigue crack initiation and short crack propagation at room temperature in an advanced disc superalloy

MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING

卷:641

Article

Jiang, R.¹  Karpasitis, N.¹  Gao, N.¹  Reed, P. A. S.¹ 

[1] Univ Southampton, Mat Res Grp, Engn & Environm, Southampton SO17 1BJ, Hants, England

关键词: Ni-based superalloys;    Twin boundary;    Schmid factor;    Slip band;    Fatigue cracking;   

DOI  :  10.1016/j.msea.2015.05.065

来源: Elsevier

【 摘 要 】

Fatigue crack initiation and early short crack propagation behaviour in two microstructural variants of a recently developed Low Solvus, High Refractory (LSHR) disc superalloy at room temperature has been investigated by three-point bending with replication procedure. The results shows that fine gained (FG) LSHR possesses higher fatigue life due to its better crack initiation resistance, limited crack coalescence and comparable Stage I crack propagation resistance to the coarse grained (CG) LSHR, although its resistance to Stage II crack propagation is inferior. Twin boundary (TB) cracking in the relatively large grains dominates the crack initiation process along with occasional crack initiation due to slip band cracking. Activation of the primary slip systems parallel to the TB at matrix and twin and high resolved shear stress associated with high Schmid factor (SF) are required for TB crack initiation. Cracks preferentially propagate along slip bands associated with high SF slip systems after initiation. But cracks also propagate along slip bands associated with slip systems with lower SF if the inclination angle between the slip band ahead of the crack tip and the crack segment of the crack tip is small enough to enable a steady transition (or non-deflected growth) of cracks across the grain boundary. (C) 2015 Elsevier B.V. All rights reserved.

【 授权许可】

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