P. Richer

Cold gas dynamic spraying of iron-base amorphous alloy

This paper describes recent efforts to synthesize iron-base amorphous alloys coatings using cold gas dynamic spraying. Characterization of the gas-atomized iron-base (Fe-Cr-Mo-W-C-Mn-Si-Zr-B) powder shows that the powder is fully amorphous when the particle diameter is below 20 µm. The coatings produced were composed of the same microstructure as the one observed in the feedstock powder. The overall deformation suggests the occurrence of a localized deformation process at the particle/particle boundary and a possible adiabatic deformation softening inside the powder particles during splat formation. The synthesis of fully amorphous, porous-free coatings using cold gas dynamic spraying was demonstrated in this work.

Substrate roughness and thickness effects on cold spray nanocrystalline Al−Mg coatings

Nanocrystalline Al−Mg coatings were produced using the cold gas dynamic-spraying technique. Unsieved Al−Mg powder of average nanocrystalline grain size in the range of 10 to 30 nm and with a particle size distribution from 10 to >100 μm was used as the feedstock powder. The resulting coatings were evaluated using scanning electron microscopy (SEM), transmission electron microscopy, as well as microhardness and nanoindentation measurements. Coating observations suggest that the wide particle size distribution of the feedstock powder has a detrimental effect on the coating quality but that it can be successfully mitigated by optimizing the spraying parameters. Nanohardness values close to 3.6 GPa were observed in both the feedstock powder and coatings, suggesting the absence of cold-working hardening effects during the process. The effects of the substrate surface roughness and thickness on coating quality were investigated. The deposited mass measurements performed on the coatings showed that the effect of using different grit sizes for the substrate preparation is limited to small changes in the deposition efficiency of only the first few layers of deposited material. The SEM observation showed that the substrate surface roughness has no significant effect on the macrostructures and microstructures of the coating. The ability to use the cold gas dynamic spraying process to produce coatings on thin parts without noticeable substrate damage and with the same quality as coatings produced on thicker substrates was demonstrated in this work.

Pin Fin Array Heat Sinks By Cold Spray Additive Manufacturing: Economics Of Powder Recycling

As a result of the rise in processing power demands of today’s personal computers, water-cooled pin fin heat sinks are increasingly being employed for the cooling of graphical processing units. Currently, these high-performance devices are manufactured through high-cost, high-waste processes. In recent years, a new solution has emerged using the cold gas dynamic spray process, in which pin fins are manufactured onto a base plate by spraying metallic powder particles through a mask allowing for a high degree of adaptability to different graphics processing unit shapes and sizes. One drawback of this process is reduced deposition efficiency, resulting in a fair portion of the feedstock powder being wasted as substrate sensitivity to heat and mechanical residual stresses requires the use of reduced spray parameters. This work aims to demonstrate the feasibility of using powder recycling to mitigate this issue and compares coatings sprayed with reclaimed powder to their counterparts sprayed with as-received powder. The work demonstrates that cold gas dynamic spray is a highly flexible and economically competitive process for the production of pin fin heat sinks when using powder recycling. The heat transfer properties of the resulting fins are briefly addressed and demonstrated.