An Attempt to Understand Stainless 316 Powders for Cold-spray Deposition

Abstract

Cold gas dynamic spray (CS) is a unique technique to deposit material using high strain rate solid state deformation. A major challenge for this technique is its dependence on the powder properties and lack of standards to assess them between lots and manufacturers. The motivation of this research was to understand the variability in powder atomization techniques for stainless steel powders and their subsequent properties for their corresponding impact on CS. A drastic difference (~30%) was observed in deposition efficiencies (DE) of unaltered, spherical, and similar sized stainless steel (316) powders produced using centrifugal (C.A) and traditional gas atomization (G.A) techniques. The study highlights more on differences on precursor level. Using recent advancements in large scale statistical measurements like laser diffraction shape analysis, µCT scanning, traditional methods like EBSD, nano-indentation, an attempt is made to understand the powder property. Insights on powder size and shape are documented. Significant differences were observed between C.A and G.A powders in terms of grain size, fraction of higher angle grain boundaries (HAGB) and nano hardness. The outcomes of this study would be helpful to understand the commercialization of the cold-spray process for bulk manufacturing of powder precursors