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7336 |
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Friday, May 06, 2022, Hall G1 11:00 AM Cold Gas Spraying III |
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Tailoring powder strengths for enhancing quality of cold sprayed Al6061 deposits |
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Chunjie Huang* / Northwestern Polytechnical Univerisity, China Thomas Klassen / Universität der Bundeswehr HamburgHelmut-Schmidt-University/University of the Federal Armed Forces Hamburg, Germany Alexander List/ Helmut-Schmidt-University/University of the Federal Armed Forces Hamburg, Germany Frank Gärtner/ Helmut-Schmidt-University/University of the Federal Armed Forces Hamburg, Germany |
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As verified by literature data, solution heat-treatments of as-atomized Al alloys powders prior to cold spray, result in a microstructural homogenization, as well as an increase in deposition efficiency. Howev-er, so far, a straightforward correlation between powder mechanical properties and consequences for the per-formance in cold spraying and attainable deposit properties is still missing. For providing a reliable, general description, the present study thus applies direct analyses of powder strengths in as-atomized and stored as well as soft annealed states to the calculation of respective critical velocities for successful layer formation in cold spraying. By using real powder data, a more realistic description of the critical velocity in CS and the respec-tive deposit quality parameter ? is obtained. This allows for deriving associated influences of powder strength on single-particle deformation and adhesion as well as on full deposit microstructures and properties. By soft annealing of as-atomized and stored powder, its strength is reduced by about 60% and respectively decreases the critical velocity for successful deposition. Consequences on deposit properties were investigated by systematic variation of impact condition via the process gas temperatures. The experimental results demon-strate that the powder strength-based calculation of the quality parameter ? allows for a more realistic descrip-tion of microstructural characteristics and deposits properties, as proved by analyses of porosity, electrical con-ductivity, and mechanical properties as microhardness and deposit strengths. The single-particle impact mor-phologies as well as the detachment features of adhering splats in cavitation tests visualize the respective depo-sition characteristics and bonding behaviors. The lower critical velocities by soft annealing contribute to better single splat adhesion, lower porosity, higher electrical conductivity, as well as an improved tensile strength of deposits. The direct correlation of powder pre-treatments and strengths in combination with cold spray parame-ter variation allows to define effective strategies for improving deposit properties. |