A study on the effect of a dynamic contact force control for improving electrospark coating properties

Abstract

Abstract The electrospark deposition (ESD) technique was used to apply aluminum-diffusion coatings over a thin stainless steel sheet under low energy discharge conditions to minimize substrate damage. In order to produce uniform coating properties over relatively large areas, automatic deposition treatments were conducted in a multi-scan mode under a dynamic control of the contact force parameter, which was realized by means of a spring-loaded electrode contact. A continuous and uniform Al coating layer was obtained indicating that a dynamic contact force system may be effective in suppressing several coating defects, which are notoriously produced with conventional ESD processes. The benefits of the dynamic force control are mostly related to the concept of a mobile electrode contact, which creates a momentary gap expansion during the spark discharge. The expanded gap is believed to reduce the effect of surface roughness on spark reproducibility and at the same time to stabilize the streamer regime of the spark breakdown, which are both essential for more uniform ESD depositions and lower cathode erosion.