High Temperature Tribology Performance of Ni alloys under Helium Environment for Very High Temperature Gas Cooled Reactors (VHTRs)
Currently the health and well-being of the global society are affected by energy source efficiency, reliability and enviromental impact. Nuclear power is one of the realiable energy resources with low greenhouse gas emissions per unit energy generated. Findings from the current research directly result in more reliable and efficient nuclear power plants. This project systematically studied the tribological (friction and wear) response of alloy 800H and Inconel 617 at very high temperatures and in the presence of helium coolant. The project targeted to address the need for mitigating the scarcity of available knowledge on the tribological performance of these alloys operating under relevant advanced reactor environments, as well as further enhancements in their tribological performance and durability. In this project, a comprehensive experimental investigation was performed to study and compare the friction, surface damage (wear, self-welding, oxidation) and contact response of tribo-pairs consisting of alloys 800H and 617 in simulated helium and also in air up to 950 °C. The results generated here contribute to the design and licensing of high temperature gas cooled reactors (HTGR) and very high temperature gas cooled reactors (VHTR) in Nuclear Regulatory Commission (NRC), especially with the forthcoming addition of Alloy 617 to the ASME Code. In addition, micro/nano-mechanical testing and material characterization were performed in high temperatures along with analytical/numerical modeling to obtain a fundamental knowledge of the failure mechanisms and tribological response, as well as to develop predictive models. The research project also investigated different solutions such as identification of optimized operating conditions and surface modifications to alleviate tribological problems with these materials under HTGR/VHTR conditions. The fundamental knowledge in high temperature tribology, especially in controlled gas atmosphere is limited, mainly due to complexity of experimental tests and analytical/numerical methods. The present work is pushing the boundaries of in-situ multiscale (nano/micro/macro) characterization of tribological materials in air/non-air ambient conditions at very high temperatures through novel experimental setups (e.g., very high temperature tribometer and very high temperature nano-indenter, under controlled Helium condiitons). Also, comprehensive surface layer composition studies using advanced electron microscopy and other material characterization techniques, provide insght into the prevention and failure mechanisms. In addition, this research impacts the surface engineering science community through identification of solutions to mitigate tribological problems under very high temperature conditions. Despite its importance, the field of tribology has not been acknowledged appropriately in different communities. The expansion of tribological science especially in the fields that deal directly with society heath, wealth, and comfort can provide tangible examples of engineering impact as well as useful and applicable science for the expert societies. This work provides new knowledge in the form of scientific papers, technical reports, and presentations that benefits a wide range of communities, and individuals. In addition, students active in the project had the opportunity to improve their hands-on skills on tribological testing, surface characterization, and nano-indentation measurements and simulations at high temperatures. Most importantly this work is showcasing the important tribological issues encountered in suture state-of-the-art nuclear reactors. Also, through close collaboration between three research universities and through effective integration of the research into graduate and undergraduate classes, the benefit of the current project have reached several members of the society.
- Research Organization:
- Texas A & M Univ., College Station, TX (United States)
- Sponsoring Organization:
- USDOE Office of Nuclear Energy (NE)
- Contributing Organization:
- Purdue University; George Mason University
- DOE Contract Number:
- NE0008549
- OSTI ID:
- 1580653
- Report Number(s):
- M2NU-16-TX-TAMU-030301-111; DUNS 847205572
- Country of Publication:
- United States
- Language:
- English
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