Effect of process parameters on deposition rate and coating roughness of electro discharge deposition on AA7075 aluminium alloy

Abstract

Nowadays, surface modification techniques are a big part of making metals and alloys better on the outside. Even though various metals and alloys are coated using surface modification techniques, improving the surface properties of the light alloys is difficult. To improve the surface properties of light alloys, electro-thermal techniques, namely electro discharge deposition (EDD), are suitable. Hence, in this investigation, a fly ash (FA)–copper (Cu) composite coating was developed on AA7075 using electro discharge deposition. The FA–Cu composite electrodes were manufactured by the powder metallurgy method. The effects of discharge current, pulse on time, and pulse off time on deposition rate (DR) and coating roughness (CR) have been studied. Tests were carried out according to the design matrix generated by central composite design in response surface methodology (RSM). An ANOVA was performed to determine the optimum parametric conditions for the responses. Pulse off time was the dominating parameter followed by discharge current and pulse on time for attaining the best response. Higher values of current, pulse on time, and pulse off time led to higher DR and CR values. Higher discharge current produced sufficient spark strength that melted both the tool electrode and the workpiece. The lower setting of parameters offered smooth roughness due to the even spark distribution. At a current of 8 A, bigger craters were observed due to the higher spark intensity that made the surface hard. The uneven mass was produced with a deeper shallow crater, resulting in a poor surface.