Powder Spray Laser Additive Manufacturing of Zirconium
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Zirconium is commonly used in nuclear, chemical processing and biomedical applications due to its low thermal neutron cross-section, relatively high corrosion resistance and great biocompatibility. Although it is an ideal candidate for laser cladding and Laser Additive Manufacturing (LAM), prior to this work very little research existed to prove that this was possible. This study used a Direct Energy Deposition (DED) method with localized shielding to successfully deposit commercially pure zirconium on zirconium alloy substrate. Effects of laser power, laser scan speed, laser spot size and powder feed rate were evaluated on deposition rate, dilution, geometrical circularity and presence of defects for single layer clads. Optimized parameters were used to deposit multilayer clads using recycled and as-received powder. Tempered as-received powder LAM deposits had higher ductility and Ultimate Tensile Strength (UTS) than commercially manufactured zirconium alloy. It is suggested that recycled powder deposits had reduced ductility due to presence of higher porosity and/or powder particles that were highly contaminated with atmospheric gases. These contaminated particles adhered poorly with the surrounding matrix and appeared as porosities during sample preparation and fracture testing. The optimized shielding gas nozzle design achieved levels of atmospheric contamination in LAM deposits comparable to conventionally manufactured zirconium alloys. Lack of adequate shielding resulted in changes in microstructure, microhardness, chemistry and appearance. Further optimization of shielding gas nozzle can allow in-situ repair of zirconium components and other reactive metals with just localized shielding.
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Arshad Harooni (2016). Powder Spray Laser Additive Manufacturing of Zirconium. UWSpace. http://hdl.handle.net/10012/11084