Initiation and growth of small fatigue cracks in a Ni-base superalloy

This article reports research on the initiation and growth of small fatigue cracks in a nickel-base superalloy at 298 and 77 K. The experimental samples were square-bar specimens with polished surfaces, loaded in four-point bending. The crack initiation sites, crack growth rates, and microstructural...

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Bibliographic Details
Published in:Metallurgical and materials transactions. A, Physical metallurgy and materials science Physical metallurgy and materials science, 1995-08, Vol.26 (8), p.2063-2073
Main Authors: MEI, Z, KRENN, C. R, MORRIS, J. W
Format: Article
Language:English
Subjects:
Applied sciences
Exact sciences and technology
Fractures
Mechanical properties and methods of testing. Rheology. Fracture mechanics. Tribology
Metals. Metallurgy
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Summary:This article reports research on the initiation and growth of small fatigue cracks in a nickel-base superalloy at 298 and 77 K. The experimental samples were square-bar specimens with polished surfaces, loaded in four-point bending. The crack initiation sites, crack growth rates, and microstructural crack paths were determined, as was the large-crack growth behavior, both at constant load ratio and at constant maximum stress intensity. Small surface cracks initiated predominantly at (Nb, Ti)(x)C(y) inclusion particles, and, less frequently, at grain boundaries. Small cracks grew predominantly along 111-planes in individual grains and were perturbed or arrested at grain boundaries. For values of Delta K above the large-crack threshold, the average rate of small-crack growth was reasonably close to that of large cracks tested under closure-free conditions. However, short-crack growth rates varied widely, reflecting the local heterogeneity of the microstructure. (Author)
ISSN:1073-5623
1543-1940
DOI:10.1007/BF02670678