Investigation of the Effect of Surface Oxide on the Critical Impact Velocity during the Cold Spray Process of High Purity Aluminum Powder
Committee: Investigation of the Effect of Surface Oxide on the Critical Impact Velocity during the Cold Spray Process of High Purity Aluminum PowderExecutive SummaryThe objective of the proposed research is to understand the particle/substrate interaction of micron-sized High Purity (HP) aluminum (Al) powder particles with varying thickness of surface oxide/hydroxide layers, during single particle impact and determine the critical impact velocity (CIV). Advancements in analytical techniques enable in-situ supersonic impact of individual metallic micro-particles on substrates with micro-scale and nanosecond-level resolution. This allows direct observation and measurement of a material-dependent threshold velocity, above which the particle undergoes impact-induced material ejection and adheres to the substrate, (critical impact velocity). This data will then be compared to empirical as well as predicted values of the CIV from published data that are based upon theoretical iso-entropic fluid dynamics models. A major emphasis of this research is to perform, in-depth characterization of the Al powder in the as-received, gas atomized state and subsequent to controlled temperature and humidity exposure (designed to form a prescribed oxide and/or hydroxide surface layer) and finally after single particle impact. Analytical techniques including XPS, ICP, IGF, TEM and SEM will be performed to determine the species of oxide and/or hydroxide, bulk chemical composition, oxygen content and thickness of the surface oxide/hydroxide layer. Finally, bulk samples of material will be produced by the cold spray process, from powder representing select test groups and subsequently characterized to determine tensile and hardness properties, chemistry, microstructure and conductivity. A fundamental understanding of the role of surface oxidization in relationship to particle deformation during impact and the bonding mechanism will be applicable toward the development of optimized parameters for the cold spray (CS) process. Results from this study will aid in the development of industrial practices for producing, packaging and storing Al powders.
Prof. Richard Sisson - Advisor
Prof. Diran Apelian
Prof. Danielle Cote
Dr. Tim Eden - Pennsylvania State University
Dr. Christian Widener - South Dakota School of Mines