Taguchi optimization of the thickness of a coating deposited by LPCS

The low-pressure cold spray (LPCS) technique is used to produce conducting, anticorrosive, insulating, etc., coatings. In order to increase the efficiency of the process the latter is often automated by attaching the spraying gun to a robot or a manipulator. However, because of the large number of interdependent parameters the thickness of the run obtained in one pass of the spraying gun may range from a few hundred micrometres to as much as a few millimetres. As a result, a coating with varied surface waviness and roughness is obtained. This paper focuses on determining the optimal LPCS process parameters yielding a coating having the desired thickness. For this purpose, the Taguchi method was employed whereby the experiment could be properly designed and the principal parameters having the greatest influence on the process could be determined. The L16′ orthogonal table, four key process parameters and four levels of values for each were used. The input parameters were: powder feeding rate, spraying gun travel velocity, gas pressure and temperature. The output parameter was coating thickness. For verification purposes composite (aluminium + alumina) coatings were deposited.