Abstract
Multilayered hard coatings with a CrN matrix and an Al2O3, TiO2, or nanolaminate-Al2O3/TiO2 sealing layer were designed by a hybrid deposition process combined with physical vapor deposition (PVD) and atomic layer deposition (ALD). The strategy was to utilize ALD thin films as pinhole-free barriers to seal the intrinsic defects to protect the CrN matrix. The influences of the different sealing layers added in the coatings on the microstructure, surface roughness, and corrosion behaviors were investigated. The results indicated that the sealing layer added by ALD significantly decreased the average grain size and improved the corrosion resistance of the CrN coatings. The insertion of the nanolaminate-Al2O3/TiO2 sealing layers resulted in a further increase in corrosion resistance, which was attributed to the synergistic effect of Al2O3 and TiO2, both acting as excellent passivation barriers to the diffusion of corrosive substances.
Highlights
IntroductionDamage and failure of numerous metal components result from corrosion
In industrial applications, damage and failure of numerous metal components result from corrosion
The as-deposited chromium nitride (CrN) exhibited a pyramidlike surface with a porous columnar structure, and the pinhole defects were clearly observed, as seen in Fig. 3a, e, and i, which consisted of long columnar grains and clear grain boundaries throughout the whole coating
Summary
Damage and failure of numerous metal components result from corrosion. A variety of protective ceramic coatings, such as nitrides, carbides, silicides, and transition metal oxides, with relatively high corrosion resistance, wear resistance, and good mechanical strength, have been widely applied in the aviation, aerospace, electronics, petroleum, chemistry, machinery, textile, and automotive industries [4]. Among these protective ceramic coatings, chromium nitride (CrN) has been proven to be one of the most successfully and extensively used coatings in such industries due to its high hardness, excellent wear resistance, and remarkable stability against corrosion [5]. Depositing coatings with multilayered structures can overcome such intrinsic defects and improve the corrosion properties of hard coatings by synergistic effect of two or more materials [11, 12]
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