Cold Spray Defects: An Investigation on Very Low Scanning Speeds

The Cold Spray process is one of the best options for restoring damaged aerospace components, made of different metal alloys, including aluminum-based ones. Among the most important process parameters there are gas temperature, gas supply pressure, particle size, type of the powder and the transverse scanning speed of the gun, during processing. This last parameter represents a key factor, still poorly studied. In particular, for very low translation speeds (< 30 mm/sec), the process is capable of obtaining single-pass thicknesses exceeding 0.5 mm. Moreover, low speeds are necessarily used when particular levels of detail have to be achieved. On the other hand the authors experienced that very low transverse speeds also imply defects such as coating deficiencies at the interface between base material and coating or between the deposition layers themselves. In this paper, the results are presented regarding an experimental study on the influence of low speeds, on the porosity of the interface, for depositions of aluminum-based alloys on substrate made of the same material. The experimental study pointed out the presence of evident defects, probably related to the low scanning speed.