Magnesium alloys are lightweight materials with great potential,and plasma electrolytic oxidation(PEO)is effective surface treatment for necessary improvement of corrosion resistance of magnesium alloys.However,the∼1...Magnesium alloys are lightweight materials with great potential,and plasma electrolytic oxidation(PEO)is effective surface treatment for necessary improvement of corrosion resistance of magnesium alloys.However,the∼14µm thick and rough PEO protection layer has inferior wear resistance,which limits magnesium alloys as sliding or reciprocating parts,where magnesium alloys have special advantages by their inherent damping and denoising properties and attractive light-weighting.Here a novel super wear-resistant coating for magnesium alloys was achieved,via the discontinuous sealing(DCS)of a 1.3µm thick polytetrafluoroethylene(PTFE)polymer layer with an initial area fraction(A_(f))of 70%on the necessary PEO protection layer by selective spraying,and the wear resistance was exceptionally enhanced by∼5500 times in comparison with the base PEO coating.The initial surface roughness(Sa)under PEO+DCS(1.54µm)was imperfectly 59%higher than that under PEO and conventional continuous sealing(CS).Interestingly,DCS was surprisingly 20 times superior for enhancing wear resistance in contrast to CS.DCS induced nano-cracks that splitted DCS layer into multilayer nano-blocks,and DCS also provided extra space for the movement of nano-blocks,which resulted in rolling friction and nano lubrication.Further,DCS promoted mixed wear of the PTFE polymer layer and the PEO coating,and the PTFE layer(HV:6 Kg·mm^(−2),A_(f):92.2%)and the PEO coating(HV:310 Kg·mm^(−2),A_(f):7.8%)served as the soft matrix and the hard point,respectively.Moreover,the dynamic decrease of Sa by 29%during wear also contributed to the super wear resistance.The strategy of depositing a low-frictional discontinuous layer on a rough and hard layer or matrix also opens a window for achieving super wear-resistant coatings in other materials.展开更多
基金This work was financially supported by the Jiangsu Distinguished Professor Project,the Innovate UK(Project reference:10004694)the National Key R&D Program of China 2021YFB3401200.The Experimental Techniques Centre at Brunel University London and Nanjing University of Aeronautics and Astronautics are acknowledged.The authors also acknowledge the characterization facility at Shanghai Jiao Tong University,Central South University,University of Birmingham and University of Lille.
文摘Magnesium alloys are lightweight materials with great potential,and plasma electrolytic oxidation(PEO)is effective surface treatment for necessary improvement of corrosion resistance of magnesium alloys.However,the∼14µm thick and rough PEO protection layer has inferior wear resistance,which limits magnesium alloys as sliding or reciprocating parts,where magnesium alloys have special advantages by their inherent damping and denoising properties and attractive light-weighting.Here a novel super wear-resistant coating for magnesium alloys was achieved,via the discontinuous sealing(DCS)of a 1.3µm thick polytetrafluoroethylene(PTFE)polymer layer with an initial area fraction(A_(f))of 70%on the necessary PEO protection layer by selective spraying,and the wear resistance was exceptionally enhanced by∼5500 times in comparison with the base PEO coating.The initial surface roughness(Sa)under PEO+DCS(1.54µm)was imperfectly 59%higher than that under PEO and conventional continuous sealing(CS).Interestingly,DCS was surprisingly 20 times superior for enhancing wear resistance in contrast to CS.DCS induced nano-cracks that splitted DCS layer into multilayer nano-blocks,and DCS also provided extra space for the movement of nano-blocks,which resulted in rolling friction and nano lubrication.Further,DCS promoted mixed wear of the PTFE polymer layer and the PEO coating,and the PTFE layer(HV:6 Kg·mm^(−2),A_(f):92.2%)and the PEO coating(HV:310 Kg·mm^(−2),A_(f):7.8%)served as the soft matrix and the hard point,respectively.Moreover,the dynamic decrease of Sa by 29%during wear also contributed to the super wear resistance.The strategy of depositing a low-frictional discontinuous layer on a rough and hard layer or matrix also opens a window for achieving super wear-resistant coatings in other materials.
