Quality control of the intrinsic deposition efficiency from the controls of the splat morphologies and the deposit microstructure

A simple heuristic model was developed to demonstrate the major characteristics of impinging particles prior to impact and during the spreading stages. It is based on the determination of transfer functions between the powder particle size distribution and splat equivalent diameter distributions. The input data consist mainly of the aforementioned distributions, determined experimentally using a particle size analyzer for powder particle size analysis and the wipe test for splat equivalent diameter analysis. Output data relate to the major characteristics of the impinging particles: flattening degree, intrinsic deposition efficiency, impact velocity, etc. Comparisons of the model predictions with experimental data showed reasonable agreement. Implementation of this simple protocol provides understanding of interactions during the process and also has technological and economical impacts. It permits quality control (QC) of deposition efficiency by control of splat morphologies and aids in the definition of specifications for the powders used (for example, in terms of the lower and upper limits of the particle size distribution leading to the formation of a deposit with given processing parameters) allowing the optimization of the spray parameters to obtain high-integrity deposits.