Effect of incorporating oxygen on microstructure and mechanical properties of AlCrSiON coatings deposited by arc ion plating

AlCrSiON coatings with a 0-48 at.% oxygen addition were deposited by arc ion plating process in an Ar-N2-O2 mixture atmosphere. The influence of varying oxygen content on elemental compositions, microstructure, residual stress, and mechanical properties of the AlCrSiON coatings was investigated. The results indicate that the oxygen content increases from 0 to 48 at.% with increasing the flow ratio O2 / (O2 + N2) from 0 to 18 at.%. The AlCrSiN coating reveals a nanocrystalline structure composed of fcc-CrN and c-AlN. The c-AlN dissolves into the fcc-CrN forming the solid-solution type (Cr, Al)N as the oxygen content increases to 16 at.%. Further increasing the oxygen content up to 48 at.%, both the c-(Cr, Al)N and the c-(Cr, Al)(O,N) phases were found in the coating. The AlCrSiON coating exhibits a nano-multilayer structure repeating at ~ 8 nm intervals due to the substrate rotation. Both the hardness and the residual stress of the AlCrSiON coatings decrease as the O content increases. The adhesion strength of the AlCrSiON coatings first increases and then decreases with the increase of oxygen content. The largest recorded value of 77 N was obtained for the coating with 8 at.% oxygen. The oxygen dissolved in the coatings reveals a minor effect on the friction coefficient at room temperature. However, the average friction coefficients of the AlCrSiON coatings decrease significantly compared to that of the O free AlCrSiN coating at 600-800 °C. The AlCrSiON coatings with a low O content (≤ 16 at.%) possess a superior wear resistance at elevated temperatures. However, the over added O deteriorates the wear resistance of the AlCrSiON coatings.