A polymer-brush-based, surface-modification strategy for friction and wear reduction in hard contact under boundary-lubrication conditions is proposed, specifically for a non-aqueous environment. Surface-initiated atom-transfer radical polymerization was employed for the synthesis of three different oil-compatible, hydrophobic polymer brushes based on alkyl methacrylates. This study presents polymerization kinetics, chemical characterization by means of Fourier-transform infrared spectroscopy and surface morphologies observed in atomic force microscopy. The lubrication properties of the anchored polymers were evaluated macroscopically by means of ball-on-disk methods and on the nanonewton scale by lateral force microscopy and showed significant reduction in friction up to contact pressures as high as 460 MPa. The frictional response of surface-grafted polymers is shown to depend strongly on the compatibility of the polymer with the chosen lubricating fluid.

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Herein, role of microstructure on friction and wear properties of as‐cast and aged AZ91 alloy is investigated using atomic force microscopy (AFM) in lubricated conditions. The lubricant contains commercial antiwear additive zinc dialkyldithiophosphate (ZDDP), which reduces wear via sliding‐induced antiwear tribofilm. The tribofilm growth is found to be highly sensitive to the local microstructure of the alloy. For the case of as‐cast AZ91 alloy, the tribofilm readily forms on large Mg17Al12 precipitates, whereas α‐Mg matrix shows wear and absence of any tribofilm growth. Interestingly, for the aged alloy, the tribofilm formation on continuous precipitate (CP) and discontinuous precipitate (DP) regions is not observed. The stable sliding contact offered by large precipitates in the as‐cast microstructure is found to be critical for the tribofilm formation. Moreover, the results show a considerable difference in coefficient of friction (COF) for Mg17Al12 in the as‐cast microstructure as compared with that in the aged alloy.

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