Effect of antifriction polymer modifier on friction and wear of MAO coatings on Al–Cu–Mg aluminum alloy

Microarc oxidation allows to obtain protective coatings on the surface of aluminum alloys, including those for tribotechnical purposes. The disadvantage is a relatively high friction coefficient, as well as low resistance to shear deformation. Improving the properties of the coatings is possible through their modification by adding various additives to the electrolyte in order to increase the wear resistance of the coatings and reduce sliding friction with various materials. MAO coatings created on a commercial Al-Cu-Mg aluminium alloy were studied; a polymer modifier (finely dispersed fluoroplastic) was added to the base electrolyte in combination with Sintanol from 0.5 to 6 g/l, a total of five coatings. Friction tests were performed on tribotester MFT-5000 (Rtec, USA) in the mode of unidirectional sliding of a silicon carbide ball (diameter 10 mm) on the surface of samples in accordance with the ASTM G99 standard. Optical images of friction tracks and contact spots of the counter-body were obtained on the optical profilometer S neox 3D (Sensofar-Tech, Spain). It was found that the linear wear of the counter-body is no more than 10 μm. The values of the friction coefficient (from 0.4 to 0.6) are on average less than for the ceramic-to-ceramic contact, which is due to the presence of an antifriction modifier. The presence of a modifier in the electrolyte contributes to an increase in the porosity of the ceramic coating. The coating is wear-resistant (wear at the level of roughness) at low concentrations of the modifier. Thus, there is an optimal amount of modifier for these frictional contact conditions, which ensures a decrease in friction, but does not critically increase the porosity of the coating.