Development of empirical model and surface integrity enhancement of electro-discharge alloyed AA2024 aluminium substrate using a sintered P/M electrode

Electro-discharge alloying (EDA) is an efficient surface modification technique used for improving hardness and wear resistance. However, studies on ternary powder metallurgy (P/M) electrodes are still limited. In this investigation, Ni80–Cr10–Gr10 ternary P/M electrode was deposited on AA2024 aluminium alloy using the EDA process. The EDA variables, namely spark current (Is: 3-7A), pulse-on time (Ton: 15–25 µs) and pulse-off time (Toff: 4–8 µs) were varied to evaluate their effects on deposition rate (DR) and surface roughness (SR). Response surface methodology (RSM) was employed to develop a predictive model with a regression coefficient of 99.05% for DR and 98.05% for SR. ANOVA results identified that ‘Is’ is the most dominating factor for DR and SR, followed by Ton and Toff. Energy-dispersive spectroscope (EDS) confirmed the presence of Ni (23.47 wt.%), Cr (15.32 wt.%) and C (6.58 wt.%) on the coated surface. The average coating thickness was 125 µm. SEM analysis revealed deep craters at 7A, micro-voids at 15 µs, and agglomeration at 8 µs. The maximum DR of 0.3854 g/min and minimum SR of 4.1622 µm were attained at Is:5 A, Ton:19 µs and Toff:7 µs, with prediction error of 2.62% and 3.51%, respectively, and a composite desirability value of 0.9613.