Structure, phase transformation and corrosion resistance of CrAlN/CNx composite multilayer films in NaCl aqueous solution

摘要

Nanolayered CrAlN/CNx multilayer films (MFs) with varying modulation periods (thickness of the CNx layer: L-CNx) were deposited by ion beam assisted magnetron sputtering. The morphologies and microstructures of these films were investigated. Results indicated that the CNx layer in the CrAlN/CNx-MFs transferred from an amorphous structure into polycrystalline body-centered cubic C3N4 when its thickness was less than 1.6 nm. The corrosion behavior of these CrAlN/CNx-MFs was investigated by polarization test and electrochemical impedance spectroscopy in a 3.5 wt% NaCl aqueous solution. Results showed that the multilayer structure could effectively increase the corrosion resistance of the alloy in the NaCl solution. The thick CrAlN layer accelerated the growth of perforative columnar defects as L-CNx, increased, which destroyed the compact structure, accelerated the infiltration of corrosive medium, and increased the probability of pitting corrosion. The CrAlN/CNx-MFs had a 1.6 nm thickness of laminated CNx and their corrosion resistance was higher than those of the single layer CrAlN and single layer CNx because of the lack of surface cracks and pores.