NSUF 18-1519: in-situ Transmission Electron Microscopy during Ion-Irradiation Studies of Cold Spray Coatings for Accident Tolerant Cladding
The goal of the proposed RTE research, led by the University of Wisconsin, Madison (UW), is to investigate irradiation effects in oxidation-resistant coatings deposited on zirconium-alloy cladding using the cold spray deposition process. Instrument time is requested for in-situ Transmission Electron Microscope (TEM) at the Intermediate Voltage Electron Microscope (IVEM) facilities at Argonne National Laboratory (ANL). In the cold spray process, powder particles of a material are propelled at supersonic velocities on to the surface of a substrate to form a dense, adherent coating on the surface. The particle temperature is low and deposition occurs in solid state. Coating formation occurs by an adiabatic shear process of the near surface of the particles. Under the auspices of Department of Energy’s Phase 2 Accident Tolerant Fuel (ATF) program, UW in collaboration with Westinghouse Electric Company (WEC) has successfully developed Cr cold spray coatings for this application. The coatings have been successfully tested up to 1300°C in air/steam environment and mechanical testing has shown good coating ductility. However, there are still unanswered questions in regards to the radiation performance of these coating materials which must be necessarily addressed before implementation of lead test rods and assemblies. The effects of the high dislocation density caused by severe plastic deformation on the radiation damage tolerance is largely unknown and the proposed research will unravel some of these novel effects.The first question this RTE proposal will seek to answer relates to the ability of severely plastically deformed (SPD) materials to resist radiation damage due to the presence of a high density of deformation induced defects that act as sinks for irradiation defects. Since particle bonding occurs by an adiabatic shear process at the surfaces of colliding particles, the deformation can be quite high depending on the processing parameters. The process gas composition (nitrogen vs. helium/nitrogen ratios) has been investigated with increased deformation observed with higher helium content in the propellant gas. The differences in radiation damage tolerances for the varied processing conditions will be probed using in-situ TEM since it is uniquely suited for observation of deformation defect interaction with radiation defects. Initial in-situ TEM of cold spray Cr has shown increased damage tolerance to roughly 3dpa, however, different microstructures resulting from the process may change the radiation damage response. The proposed sample has a microstructure more similar to that of the coating which will be used commercially. Increased amounts of defects and/or nanoscale dynamic recrystallization from the increased plastic deformation from the adiabatic shear process may further improve the damage tolerance. The second question this RTE will seek to answer is how well heavy ion irradiation can simulate neutron radiation damage in cold spray deposited Cr coatings. Several iterations of these coatings are being exposed in reactors worldwide and one of the first iteration produced is undergoing post-irradiation-examination (PIE) after exposure to 0.8 dpa in the MIT reactor. In-situ ion irradiation and TEM of a counterpart coating (fabricated with the same cold spray conditions) will provide further insight into both the development of defects during irradiation and if ion irradiation can simulate neutron radiation damage in the cold spray deposited Cr coatings.Supporting work (outside RTE proposal): (i) Focused ion beam (FIB) milling of TEM lamella of cold spray coated samples will be performed at UW, (ii) TEM at UW of the as-deposited coatings fabricated with different techniques, (iii) neutron irradiation tests of coatings at Halden reactor, Norway, MITR, and ATR facility (tests began in 2017 and will continue in 2018).
Additional Info
| Field | Value |
|---|---|
| Abstract | The goal of the proposed RTE research, led by the University of Wisconsin, Madison (UW), is to investigate irradiation effects in oxidation-resistant coatings deposited on zirconium-alloy cladding using the cold spray deposition process. Instrument time is requested for in-situ Transmission Electron Microscope (TEM) at the Intermediate Voltage Electron Microscope (IVEM) facilities at Argonne National Laboratory (ANL). In the cold spray process, powder particles of a material are propelled at supersonic velocities on to the surface of a substrate to form a dense, adherent coating on the surface. The particle temperature is low and deposition occurs in solid state. Coating formation occurs by an adiabatic shear process of the near surface of the particles. Under the auspices of Department of Energy’s Phase 2 Accident Tolerant Fuel (ATF) program, UW in collaboration with Westinghouse Electric Company (WEC) has successfully developed Cr cold spray coatings for this application. The coatings have been successfully tested up to 1300°C in air/steam environment and mechanical testing has shown good coating ductility. However, there are still unanswered questions in regards to the radiation performance of these coating materials which must be necessarily addressed before implementation of lead test rods and assemblies. The effects of the high dislocation density caused by severe plastic deformation on the radiation damage tolerance is largely unknown and the proposed research will unravel some of these novel effects.The first question this RTE proposal will seek to answer relates to the ability of severely plastically deformed (SPD) materials to resist radiation damage due to the presence of a high density of deformation induced defects that act as sinks for irradiation defects. Since particle bonding occurs by an adiabatic shear process at the surfaces of colliding particles, the deformation can be quite high depending on the processing parameters. The process gas composition (nitrogen vs. helium/nitrogen ratios) has been investigated with increased deformation observed with higher helium content in the propellant gas. The differences in radiation damage tolerances for the varied processing conditions will be probed using in-situ TEM since it is uniquely suited for observation of deformation defect interaction with radiation defects. Initial in-situ TEM of cold spray Cr has shown increased damage tolerance to roughly 3dpa, however, different microstructures resulting from the process may change the radiation damage response. The proposed sample has a microstructure more similar to that of the coating which will be used commercially. Increased amounts of defects and/or nanoscale dynamic recrystallization from the increased plastic deformation from the adiabatic shear process may further improve the damage tolerance. The second question this RTE will seek to answer is how well heavy ion irradiation can simulate neutron radiation damage in cold spray deposited Cr coatings. Several iterations of these coatings are being exposed in reactors worldwide and one of the first iteration produced is undergoing post-irradiation-examination (PIE) after exposure to 0.8 dpa in the MIT reactor. In-situ ion irradiation and TEM of a counterpart coating (fabricated with the same cold spray conditions) will provide further insight into both the development of defects during irradiation and if ion irradiation can simulate neutron radiation damage in the cold spray deposited Cr coatings.Supporting work (outside RTE proposal): (i) Focused ion beam (FIB) milling of TEM lamella of cold spray coated samples will be performed at UW, (ii) TEM at UW of the as-deposited coatings fabricated with different techniques, (iii) neutron irradiation tests of coatings at Halden reactor, Norway, MITR, and ATR facility (tests began in 2017 and will continue in 2018). |
| Award Announced Date | 2018-09-17T00:00:00 |
| Awarded Institution | None |
| Facility | None |
| Facility Tech Lead | Wei-Ying Chen |
| Irradiation Facility | None |
| PI | Ben Maier |
| PI Email | [email protected] |
| Project Type | RTE |
| RTE Number | 1519 |