Effect of zirconium on physical properties and corrosion resistance of chromium and chromium nitride films

Abstract

Corrosion is a common phenomenon which usually undergoes on metal surface leading to structural failure. Consequently, this topic has attracted many researchers to look for ways to prevent corrosion and extend lifetime of service. Coating with chromium (Cr) or chromium nitride (CrN) is the one popular technique, given the high corrosion resistance and obviating whole part replacement. However, the conventional film’s properties might not provide enough resistance for using in some severe environments. Tailoring structure to amorphous is usually considered for improve corrosion resistance.

Thin amorphous featureless of CrZr-film was successfully fabricated by magnetron co-sputtering. The suitable composition (46 %at.Zr) with low energetic adatoms due to low sputtering power, restricted adatoms diffusion and nucleation in a similar way to frozen them like amorphous structure. The amorphous featureless in CrZr-film contributed to the excellent anti-corrosion property as seen by the high value of Rfilm, Ecorr with low Icorr and passivation ability. The co-existing of Cr and Zr played the important role for reducing dissolution of zirconium oxide (ZrO2) which was the major compound in CrZr-passive film.

For nitride films, the CrZrN could be fabricated by reactive magnetron co-sputtering. Complex nitride of Cr and Zr, (Cr,Zr)N, was the predominant phase in all sputtering films. Addition of Zr with higher concentration refined crystallite size of (Cr,Zr)N due to strain confinement and simultaneously promote an amorphous Zr2ON2. Addition of Zr at 0.578 atomic fraction was enough for promoting amorphous phase which was high enough content for detectable by XRD.

Modification interface between matrix and film is one parameter affecting film's crystillinity. This work revealed that addition of amorphous CrZr-interlayer could promote amorphous structure in the top nitride film by performing as “random atomic arrangement template” for top film. It was effective method for promoting amorphization as seen by no evidence of crystallinity in XRD result. This amorphous featureless nitride film contributed the excellent corrosion resistance due to less of susceptible points and columnar structure.