Effects Of Sputtering Current Of Chromium On Microstructures And Properties Of Carbon-Chromium Coatings

C-Cr coatings were deposited on high-speed steel, aluminium alloy and Si wafers by closed field unbalanced magnetron sputter iron plating technique. The chemical composition and microstructures of the coatings were analyzed by XPS, SEM, AFM, XRD and TEM. The thickness of the coatings were measured using a ball crater device, the hardness of the coatings were measured using a Vickers microhardness tester, the coating-substrate adhesion of the coatings were measured using a Rockwell hardness tester and a scratch tester, and the tribological properties of the coatings were measured using a ball-on-disk tester. The effects of sputtering current of Cr on the microstructures and tribological properties of the coatings were investigated, and the mechanisms about the effects of sputtering current of Cr on the tribological properties of the coatings were also discussed in this thesis.The investigative results indicated that the C-Cr coatings were composed of Cr layer, Cr-C/Cr transition layer and C/Cr composite layer, and a gradient structure of "crystallineâ†'nanocrystalline/amorphousâ†'amorphous" was formed. With increasing sputtering current of Cr, the fibrous and columnar structures appeared in the coatings, but the crystal structures of the coatings did not change. The chromium bond existed as Cr-Cr, Cr-O, and Cr-C in C/Cr composite layer with higher sputtering current of Cr, the content of Cr-Cr bond was in the majority, and a periodic multilayered structure was formed in C/Cr composite layer. The Cr content of the coatings increased, the sp~3 carbon bond content of the coatings decreased, and the sp~2 carbon bond content at first increased and then decreased with increasing sputtering current of Cr. The hardness of coatings decreased, the coating-substrate adhesion and toughness of the coatings increased with increasing sputtering current of Cr. When tested in water and oil, the friction coefficients of the coatings varied slightly. When tested in air, the friction coefficients of the coatings at first decreased and then increased with increasing sputtering current of Cr. The specific wear rates of the coatings increased under a 2N-load with increasing sputtering current of Cr, and the specific wear rates of the coatings varied slightly under a 10N-load.The chemical composition and microstructures of the C-Cr coatings varied with increasing sputtering current of Cr, and led to the variations of the hardness and toughness of the coatings, which caused the variations of the tribological properties of the coatings. The wear-resistant properties of the coatings were determined by hardness under a lower load, and the influence of the toughness strengthened under a higher load.