How surface treatment of porous copper samples dictates dry friction and wear

• Friction in porous copper: 0.25 after vibro- and 0.65 after electropolishing. • Friction rises with roughness from 0.11 µm for vibro- to 1.63 µm for electropolished. • Higher surface roughness increases subsurface deformation depth from 0.1 µm to 3.8 µm. • Differences detected in tribo-oxidation, cracking, delamination, wear behavior. • Vibropolishing keeps friction below 0.3 for 5000 cycles (33.3 h) in porous copper. Surface treatments such as electropolishing and chemical–mechanical vibropolishing are widely used to enhance surface quality in medical technology, semiconductor, and aerospace. Copper, commonly used in heat exchangers and electronics, can benefit from improved tribological behavior to increase efficiency, reliability, and lifespan. This study investigates how surface treatments affect tribological performance and evaluates the long-term effectiveness of the more promising treatment. Specimens with varying porosity were either vibropolished or electropolished and tested using a reciprocating ball-on-flat tribometer for 1000 and 5000 cycles. Electropolishing enlarged sintering pores. This led to an increase in S a from 0.1 to 1.6 µm, higher surface stresses, as well as more deformation; causing deeper wear tracks and pronounced grooves, smeared pores, and finer grains. These friction-induced changes include formation of new grain boundaries, promoting tribo-oxidation, cracking, and delamination. In contrast, vibropolished surfaces show minimal subsurface deformation. These mechanisms correlate with a coefficient of friction of 0.25 after vibropolishing and 0.65 after electropolishing. Long-term performance was assessed by examining whether vibropolished specimens, despite minimal subsurface deformation, behave similarly to electropolished ones. High-porosity vibropolished samples kept friction below 0.3 over 5000 cycles, despite increased tribo-oxidation, while the low-porosity one developed cracks, delamination, maintaining high friction around 0.65.