Volume-Based Deposition Factor - A Practical Approach to Estimate Deposition Efficiency

Deposition efficiency is an important indicator for the productivity of a thermal spray process. However, it requires dedicated samples and accurate measurements of weight before and after the spray process. On the other hand, there is the coating thickness or thickness per pass that can be measured directly at the sample or in the microscopy cross section. But in this case, crucial process parameters like feed rate, surface speed and for suspension spraying the solid content are not taken into account.

Therefore, a volume based deposition factor was developed that accounts for all variables in a typical spray parameter set while with a known coating thickness no additional measurements or special samples are needed. The correlation to traditional deposition efficiency will be demonstrated with various plasma and HVOF processes using powder and suspension as feedstock material. Also, the influence of coating porosity is discussed and it is shown how to take it into account as an additional factor.

The volume based deposition factor has advantages in high-number design of experiments, industrial scale production and can also be used to re-evaluate existing data sets where only spray parameters and coating thickness are documented.