Simulation of microdischarges during plasma electolytic oxidation: Influence of uncertain model inputs*

In the transportation and medical industries, the increasing use of light metals like aluminium, magnesium, and titanium and their alloys make corrosion and wear protection crucial. These can be improved by submerging these metals in electrolyte solutions and carrying out plasma electrolytic oxidation (PEO) to create a protective passivation layer on the surfaces. A significant challenge in controlling and optimising the PEO process is that the composition of the plasma and associated vapour bubbles formed is poorly understood. This work uses 0-D plasma-chemical kinetics simulations to get insight into the temporal evolution of charged and neutral particle densities in these systems.

These simulations use experimentally measured data for power deposition and bubble size as input. Since this is difficult to measure, particularly during the early stages of microdischarge formation, it represents a significant uncertainty in the model inputs. To assess the importance of this uncertainty, simulations are carried out under different assumptions to calculate this power density. Since it is challenging to simulate the EEDF accurately in these discharges, this also represents a major uncertainty. The sensitivity of the simulation outputs to the EEDF shape will also be presented and discussed.