Characterization of as-deposited cold sprayed Cr-coating on Optimized ZIRLO™ claddings

As-produced Cr-coated Optimized ZIRLO (TM) cladding material fabricated with the cold-spray (CS) deposition process is studied. Cross-sectional electron microscopy, nano-hardness profiling, transmission electron microscopy, transmission Kikuchi diffraction, and atom probe tomography (APT) were performed to investigate the nature of the CS Cr-coating/Optimized ZIRLO (TM) interface, the microstructure of the coating, and the effects of the deposition on the Zr-substrate microstructure. The former surface of the Zr-substrate was found to have a highly deformed nano-crystalline microstructure, the formation of which was attributed to dynamic recrystallization occurring during coating deposition. This microstructural change, evaluated with electron backscattered diffraction and nano-hardness profiling, appeared to be confined to a depth of a few microns. Through APT analysis, a 10-20 nm thick intermixed bonding region was observed at the interface between coating and substrate. The chemical composition of this region suggests that this layer originated from a highly localized shearing and heating of a thin volume of the outermost former surface of the substrate. The study of the intermixed bonding region's crystalline structure was performed with high resolution transmission electron microscopy and revealed a distorted hexagonal close-packed structure. (C) 2021 The Authors. Published by Elsevier B.V.

Automated summary

The study investigated the nature of the CS Cr-coating/Optimized ZIRLO (TM) interface, the microstructure of the coating, and the effects of the deposition on the Zr-substrate microstructure. Results showed that during coating deposition, the former surface of the Zr-substrate underwent significant microstructural changes, forming a highly deformed nano-crystalline microstructure, and a 10-20 nm thick intermixed bonding region was observed at the interface between coating and substrate.