iTSSe TSS ADVANCED MATERIALS & PROCESSES | APRIL 2024 37 iTSSe TSS FEATURE 8 Thermal spray (TS) emerged in the early 1900s as a technology capable of depositing various materials (ceramics, metals, and polymers) to form coatings with a diversity of mechanical and chemical properties. It has since been utilized in a wide range of industries including the oil and gas, electronics, biomedical, and power and energy sectors, to name a few[1,2]. Aside from engineering applications, TS processes have been used in the arts for drawing logos, repairing sculptures, and protecting wood from biological degradation while providing aesthetic characteristics[3]. These endeavors have mostly been accomplished using high temperature thermal spray processes. Cold gas dynamic spray (CGDS), a solid-state thermal spray process, has not been widely used to enhance or create large artworks. The project discussed here explores the development of Deep Time, a work of art created with six different metals, by evaluating the deposition resolution, deposition efficiency, and powder color palette. BACKGROUND The Deep Time project aims at replicating in 3D, on a 30 x 24 in. metallic canvas, the morphology, key features, and important details of a crinoid fossil discovered on Anticosti Island in Quebec, Canada, using the CGDS process as an art tool (Fig. 1). Anticosti Island is more than just the backdrop for this project—it holds the key to understanding a crucial moment in Earth’s history. This island’s limestone rocks contain countless well-preserved fossils spanning 15 million years, from the Upper Ordovician to Lower Silurian periods nearly 450 million years ago. Recently recognized by UNESCO as a World Heritage Site, Anticosti Island offers scientists a unique window into the world’s first mass extinction, offering invaluable insights into the prehistoric past. MATERIALS To reproduce the color palette found in the original fossil photograph, eight different powders were selected based on their initial as-received color. Spherical (Valimet, H35, CA, USA) and irregularly shaped (CenterLine, SST-A5001, ON, Canada) commercially pure aluminum, irregularly shaped zinc (CenterLine, SST-Z5001, ON, Canada), water atomized irregularly-shaped steel (Rio Tinto, Atomet 1025, Quebec, Canada), spherical titanium alloy (Ti64, Tekna, Ti64 53/20, Quebec, Canada), spherical (Hoganas, Amperit 176, AB, Sweden) and irregularly shaped (CenterLine, SST-N5001, ON, Canada) nickel and a nickel-base blend (CenterLine, SST-N0056, ON, Canada). The choice of two different morphologies for a specific powder was made to allow greater subtlety of the as-sprayed color palette, which is affected by the resulting as-sprayed surface roughness. The latter affects light reflection and can provide a rich palette according to the potential assprayed surface topology. Figure 2 shows particle geometry and size using scanning electron microscopy (SEM) alongside visible color palette pictures in a well-lit environment under a solar light source. To provide sufficient target surface deformation upon CGDS particle impact, while still offering rigidity and bending resistance to potential residual stress buildup, an aluminum PAINTING WITH METAL: WHEN HISTORY AND ART MEET THERMAL SPRAY Cold spray technology provides a multidisciplinary approach to additive manufacturing at the intersection of science and art. Aleksandra Nastic and Bertrand Jodoin, FASM* Cold Spray Laboratory, University of Ottawa, Canada Christine Fitzgerald Photo-based artist, Ottawa, Canada Sylvain Desaulniers,* Luc Pouliot, FASM,* Daniel MacDonald, Fernanda Caio,* Guillaume Dubois, Alexandre Duval, Vincent Tessier, and Christopher Etienne Polycontrols, Brossard, Canada *Member of ASM International Fig. 1 — (a) Crinoid fossil from Anticosti Island stored at Natural Resources Canada in Ottawa; and (b) cropped section used for the artwork. (a) (b)
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