Application of a modified hyperbolic sine creep rate equation to correlate uniaxial creep rupture data of Sanicro 25 and HR6W

ABSTRACT

Uniaxial creep life data is still used to estimate long-term creep strength and maximum allowable design stresses for structural materials. Many ‘single-line’ equations have been developed to correlate uniaxial creep life data, such as the Larson-Miller Parameter (LMP) and Wilshire (WS) equations; few are derived from the physics of creep. Some forms of these equations can be mathematically inconsistent with the behaviour of metals at high temperatures, making them potentially unreliable predictors of long-term life. Two modified hyperbolic sine minimum creep rate equations combined with the Monkman-Grant equation were used to correlate uniaxial creep life data of Sanicro 25 and HR6W, and then calculate their long-term creep strength. A modified hyperbolic sine equation was selected because it has a physical basis in dislocation creep and is numerically stable. It was found that the modified hyperbolic sine equations fit the experimental data as well as the LMP and WS equations.

KEYWORDS:

• Creep
• creep rupture
• Monkman-Grant equation
• Larson-Miller equation
• Wilshire equation
• hyperbolic sine equation
• Sanicro 25
• HR6W

Acknowledgments

This research was supported in part by the National Energy Technology Laboratory (NETL), sponsored by the U.S. Department of Energy (DOE) Office of Fossil Energy (FE) Mickey Leland Energy Fellowship (MLEF) program, and administered by the Oak Ridge Institute for Science and Education (ORISE).

Disclaimer

This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference therein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed therein do not necessarily state or reflect those of the United States Government or any agency thereof.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

KeyLogic Systems, Inc.’s contributions to this work were funded by the National Energy Technology Laboratory under the Mission Execution and Strategic Analysis contract [DE-FE0025912] for support services, and occurred while co-author Mark Render was an employee of KeyLogic Systems, Inc.