Study On Corrosion Properties Of Atomic Layer Deposited Oxide Based Films

In this paper,TiO₂ films and Ti-based fumaric acid hybrid coatings were deposited by atomic layer deposition system on Si?100?wafers.After annealing,the TiO₂ coatings and C-TiO₂ coatings with different annealing temperatures were obtained.Meanwhile,the atomic layer depositied TiO₂ and Al₂O₃coatings were deposited on 316L stainless steels and Si?100?wafers.Finally,a series of TiN/Al₂O₃/TiN composite coatings were deposited on 316L stainless steels and Si?100?wafers by the combination of atomic layer deposition and magnetron sputtering.X-ray diffraction,X-ray photoelectron spectroscopy and scanning electron microscopy were used to analyze the phase structures,compositions,surface and cross-sectional profiles of coatings.The adhesion strength between the coatings and substrates,hardness,elastic modulus and surface roughness of coatings were analyzed by scratch tester,nano-indentation tester and three dimensional profilometer.The corrosion resistances of the coatings were investigated by an electrochemical workstation in 3.5wt.%NaCl solution.After corrosion,the surface morphology of the coating was observed by the optical microscope.The corrosion mechanism was also discussed.Additionally,the tribological properties of the coatings were tested by a ball-on-disk tribometer in 3.5wt.%NaCl solution.The wear tracks on coatings were analyzed by an optical microscope and three dimensional profilometer.The main achievements are summarized as follows:1)All of the unannealed coatings are amorphous,and the surface morphologies of the coatings are smooth.The TiO₂ coatings are the island growth mode.While the C-TiO₂ coatings show the layered growth mode.As the increase of annealing temperature,the crystalline phase of TiO₂ and C-TiO₂coatings transforms from the anatase phase to rutile phase.For TiO₂ coatings,the grains and surface roughness of the coatings become larger,and the corrosion resistances are improved.For C-TiO₂coatings,the grain sizes increase,and the roughness decreases firstly and then increases,the corrosion resistances are enhanced.2)Both the as-prepared Al₂O₃ and TiO₂ coatings are amorphous with the island growth mode.The surfaces of Al₂O₃ coatings are smooth and compact without any obvious pores and cracks.While there are a few white spots existed in the smooth surface of TiO₂ coatings.Compared with bare 316L stainless steel,Al₂O₃ and TiO₂ coatings have better corrosion resistances in 3.5 wt.%NaCl solution.For the TiO₂coatings,the solution began to infiltrate into the coatings at the initial soaking time.The Al₂O₃ coatings can effectively prevent the infiltration during the initial soaking period.At the mid-soaking time,the anti-infiltration ability of the coating turns worse.With the further increase of the soaking time,the coatings become completely invalid.3)TiN coatings with the columnar growth have large surface roughness and low surface hardness.For the TiN/Al₂O₃/TiN compsite coatings with the amorphous Al₂O₃ interlayers,when the insertion position of the Al₂O₃ interlayer is shifted upward,the particles on the surface and surface roughness of the coatings turn smaller,the surface become denser.The adhesion strength between the coatings and substrates increases.The hardness,H/E and H³/E² of the coatings become larger.Compared with pure TiN coating,the composite coatings show better corrosion resistance and anti-friction performance in3.5 wt.%NaCl solution.Shifted up the Al₂O₃ interlayers,the anti-corrosion behavior of the composite coatings turns further better.While the TiN/Al₂O₃/TiN composite coatings show better anti-friction properties than the TiN coatings.