NSUF 17-1069: Atomic Probe Tomography Studies of Irradiated 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 Atomic Probe Tomography (APT) and associated focused ion beam (FIB) APT sample preparation instruments at Idaho National Laboratory (INL). 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 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 and FeCrAl 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 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 first question this RTE proposal will seek to answer relates to the inevitable thin native oxide layer (~1 to 10 nm) on the surfaces of the powders, the precursor for the cold spray process. Since particle bonding occurs by an adiabatic shear process at the surfaces of colliding particles, the deformation and fracture behavior of this thin oxide layer plays a critical role in the formation of the coating. The APT technique is uniquely suited for identifying the spatial distribution of oxygen atoms at the interparticle boundaries (IPB). Radiation is known to cause interfacial mixing and is expected to promote bonding at IPBs. The oxygen atoms can in effect act as ‘markers’ to identify the extent of interfacial mixing at the IPBs. This phase of the RTE will be performed using Cr cold spray coatings.
The second question this RTE will seek to answer is the formation of brittle Cr-rich alpha-prime phase precipitates in FeCrAl alloys under radiation. Recent work led by Oak Ridge National Laboratory and UW has shown that the formation of alpha-prime precipitates depends on the initial microstructure of the alloy.5 In this regard the microstructure of cold sprayed FeCrAl alloy is very unique, consisting of a very high density of dislocations compared to conventional microstructures investigated thus far. Thus, it is of considerable scientific interest to understand the evolution and growth of alpha-prime precipitates in cold spray coating microstructures.
Supporting work (outside RTE proposal): (i) Ion irradiation of cold spray coated samples is being performed at UWs accelerator facilities using 3 MeV Fe+2 ions to a damage level of 100dpa (to be completed at UW by 6/10/17), (ii) TEM of the ion irradiated coatings (to be completed at UW by 9/31/17), (iii) neutron irradiation tests of coatings at Halden reactor, Norway, MITR, and ATR facility (tests to begin in 2017).
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 Atomic Probe Tomography (APT) and associated focused ion beam (FIB) APT sample preparation instruments at Idaho National Laboratory (INL). 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 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 and FeCrAl 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 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 first question this RTE proposal will seek to answer relates to the inevitable thin native oxide layer (~1 to 10 nm) on the surfaces of the powders, the precursor for the cold spray process. Since particle bonding occurs by an adiabatic shear process at the surfaces of colliding particles, the deformation and fracture behavior of this thin oxide layer plays a critical role in the formation of the coating. The APT technique is uniquely suited for identifying the spatial distribution of oxygen atoms at the interparticle boundaries (IPB). Radiation is known to cause interfacial mixing and is expected to promote bonding at IPBs. The oxygen atoms can in effect act as ‘markers’ to identify the extent of interfacial mixing at the IPBs. This phase of the RTE will be performed using Cr cold spray coatings. The second question this RTE will seek to answer is the formation of brittle Cr-rich alpha-prime phase precipitates in FeCrAl alloys under radiation. Recent work led by Oak Ridge National Laboratory and UW has shown that the formation of alpha-prime precipitates depends on the initial microstructure of the alloy.5 In this regard the microstructure of cold sprayed FeCrAl alloy is very unique, consisting of a very high density of dislocations compared to conventional microstructures investigated thus far. Thus, it is of considerable scientific interest to understand the evolution and growth of alpha-prime precipitates in cold spray coating microstructures. Supporting work (outside RTE proposal): (i) Ion irradiation of cold spray coated samples is being performed at UWs accelerator facilities using 3 MeV Fe+2 ions to a damage level of 100dpa (to be completed at UW by 6/10/17), (ii) TEM of the ion irradiated coatings (to be completed at UW by 9/31/17), (iii) neutron irradiation tests of coatings at Halden reactor, Norway, MITR, and ATR facility (tests to begin in 2017). |
| Award Announced Date | 2017-09-20T12:36:31.007 |
| Awarded Institution | None |
| Facility | None |
| Facility Tech Lead | Yaqiao Wu |
| Irradiation Facility | None |
| PI | Ben Maier |
| PI Email | [email protected] |
| Project Type | RTE |
| RTE Number | 1069 |