SYMPOSIA PAPER Published: 01 January 1988
STP33111S

Near-Threshold Crack Growth in Nickel-Base Superalloys

Source

The influence of stress ratio on the elevated-temperature crack growth behavior of the nickel-base superalloys René 95 and Alloy 718 is discussed. The near-threshold and Region II crack growth behavior of a wide variety of microstructures for each alloy are explained using phenomenological descriptions of closure, that is, K-dependent or K-independent closure. K-dependent closure is the type of closure observed for nickel-base superalloys where increasing the R-ratio causes a uniform lateral shift of the entire fatigue crack growth curve. K-independent closure is the type commonly reported for steels and titanium alloys where increasing the R-ratio has a larger influence on near-threshold crack growth than on Region II crack growth. The existence of K-dependent closure in nickel-base superalloys results in microstructurally sensitive crack growth rates, even at high R-ratios. This permits the use of K-based crack growth prediction techniques and simplifies alloy and process development for applications having complex loading spectra.

Author Information

Van Stone, HR
General Electric Co., Cincinnati, OH
Krueger, DD
General Electric Co., Cincinnati, OH
Price: $25.00
Contact Sales
Related
Reprints and Permissions
Reprints and copyright permissions can be requested through the
Copyright Clearance Center
Details
Developed by Committee: E08
Pages: 883–906
DOI: 10.1520/STP33111S
ISBN-EB: 978-0-8031-5041-6
ISBN-13: 978-0-8031-0972-8