In the current study, steel coatings were deposited on pure copper and copper-alumina composite substrates using the electro-spark deposition (ESD) method. The objective was to investigate the influence of substrate type on the morphology and tribological properties of the coatings. Results showed that the surface roughness of the coatings on pure copper and the composite were 7 μm and 11 μm, respectively. The hardness values of the coatings were measured as 662 HV on copper and 748 HV on the composite. Microscopic observations revealed the formation of micro-cracks in the composite coating due to local differences in the thermal expansion coefficient and the presence of hard alumina particles. The Orowan strengthening mechanism, in the presence of alumina particles, enhanced the hardness of the coating. Electrochemical tests in a 3.5 wt.% NaCl solution revealed that the coating on the composite substrate exhibited a higher corrosion current density and lower corrosion resistance compared to the coating on pure copper, which is attributed to the micro-cracks providing pathways for corrosive species. Copper's low inherent friction coefficient resulted in a lower initial friction value. However, its performance degraded over time due to oxidation. Conversely, the composite material showed better performance in the test's later stages. This suggests copper primarily experienced adhesive wear, while the composite's wear was predominantly abrasive. Overall, the results indicate that substrate selection plays a key role in controlling the composition, tribology and corrosion properties of ESD coatings. • Substrate type critically controls coating morphology and integrity. The heterogeneous Cu-Al 2 O 3 composite yielded a rougher coating (11 μm) than pure copper (7 μm) due to hindered heat and mass transfer around hard alumina particles. • Micro-cracks form in the composite coating due to local thermal expansion mismatch and stress concentration on alumina particles, while the ductile copper substrate prevents cracking. • Coating hardness is enhanced by 13% (748 HV) on the composite substrate via the Orowan strengthening mechanism, where nano-alumina particles act as obstacles to dislocation motion. • The dominant wear mechanism shifts with the substrate: adhesive wear for copper and abrasive wear for the composite, affecting the friction coefficient evolution over time. • Corrosion resistance is superior on the pure copper substrate. Micro-cracks in the composite coating double the corrosion rate by providing pathways for chloride ions.
Ahmadkhanpour et al. (Sun,) studied this question.