Structure and corrosion properties of PVD Cr–N coatings

Abstract

Corrosion behavior of Zr modified CrN coatings using metal vapor vacuum arc ion implantationPVD Cr-N coatings produced by physical vapor deposition ͑PVD͒ are increasingly used for mechanical and tribological applications in various industrial sectors. These coatings are particularly attractive for their excellent corrosion resistance, which further enhances the lifetime and service quality of coated components. PVD Cr-N coated steels in an aqueous solution are usually corroded by galvanic attack via through-coating ''permeable'' defects ͑e.g., pores͒. Therefore, the corrosion performance of Cr-N coated steel is determined by a number of variables of the coating properties and corrosive environment. These variables include: ͑i͒ surface continuity and uniformity; ͑ii͒ through-coating porosity; ͑iii͒ film density and chemical stability; ͑iv͒ growth stresses; ͑v͒ interfacial and intermediate layers; ͑vi͒ coating thickness; ͑vii͒ coating composition; and ͑viii͒ substrate properties. In this article, PVD Cr-N coatings were prepared, by electron-beam PVD and sputter deposition, with different compositions, thicknesses, and surface roughnesses, by changing the N 2 flow rate, applying multilayering techniques and changing the substrate finish prior to coating. The microstructure of such coatings is investigated by various analytical techniques such as glancing angle x-ray diffraction and scanning electron microscopy, which are also correlated with the corrosion performance of the coated steel. Both dc polarization and ac impedance spectroscopy were employed to investigate the corrosion resistance of Cr-N coated steel in a 0.5N NaCl solution. It has been found that the N 2 flow rate during reactive deposition strongly determines the microstructure of Cr-N coatings ͑due to the changing nitrogen content in the film͒ and can thus affect the corrosion resistance of coated systems. The surface finish of the steel substrate also affects the uniformity and coverage of PVD coatings; grooves and inclusions on the original substrate can raise the susceptibility of coated systems to crevice corrosion. Increased coating thickness can also greatly reduce the incidence of through-coating porosity such that the improvement in corrosion performance of thicker Cr-N coatings is significant.

Structural and mechanical properties of compositionally gradient CrNx coatings prepared by arc ion plating

“…Increasing attention has been paid to chromium nitride (CrN) coatings due to its favorable properties, such as good oxidation resistance [1], excellent wear and corrosion resistance [2]. Owning an environment-friendly feature and pretty color of shining silver, CrN coating synthesized by physical vapor deposition (PVD) has been regarded as a good substitution for electroplating chromium coatings, which contain hazardous hexavalent chromium and bring in badly pollution in electroplating process.…”

The effect of coating architecture and defects on the corrosion behaviour of a PVD multilayer Inconel 625/Cr coating

“…There are many ways which have been proposed for the improvement in the corrosion-barrier performance of PVD coatings, such as the use of thicker coatings, multilayering, intermediate etching, alloying and through the elimination of droplets by modification of the deposition process [19][20][21][22]. During intermediate etching, the grown film surface is bombarded by ions.…”

The effect of Zircaloy-4 substrate surface condition on the adhesion strength and corrosion of SiC coatings

“…doi:10.1016/j.jnucmat.2005.05.016 difference in corrosion potential between metal and coating material exists at the coating/substrate interface in through-coating defects. However, it is possible to enhance the corrosion performance of ceramic coatings by improving adhesion [7,8]. Several acceptable techniques have been proposed to increase the adhesion.…”

“…These variables include surface continuity and uniformity, coating defects, adhesion, and substrate roughness [7][8][9][10][11].…”