Toward high load bearing capacity and corrosion resistance Cr/Cr2N nano-multilayer coatings against seawater attack

• Cr/Cr2N nano-multilayer coatings were fabricated by multi-arc ion plating.
• Coating with proper thickness ratio of Cr and Cr2N layer possessed high toughness.
• Corrosion behavior of multilayer coating depended on porosity and interface effect.
• High toughness and tribolayer contributed to good tribological behavior of coating.

Cr/Cr2N nano-multilayer coatings with varied individual thickness of Cr2N layer were fabricated on 316L stainless steel substrates by multi-arc ion plating system. The evolutions of microstructures and mechanical properties were investigated by scanning electron microscopy, X-ray diffraction, nanoindentation and scratch testing. The corrosion behaviors and tribological properties in seawater conditions were evaluated using polarization resistance and reciprocating-sliding friction tests, respectively. Results showed that the multilayer coatings with thicker individual Cr2N layer presented higher hardness at the expense of toughness, and the coating with thickness ratio of Cr and Cr2N layers at 0.45 possessed both high hardness and toughness. The dominant feature influencing the corrosion resistance of deposited multilayer coating was the porosity and interface effect. While the excellent tribological performances of coatings with high load bearing capacity were attributed to the optimization of thickness ratio presenting high mechanical properties. Furthermore, the tribolayer formed during wear process, which small debris particles of chromium nitride embedded into the lubricative matrix and well adhered in the wear track, played a significant role in the anti-wear property. The superior anti-corrosion and anti-wear performances of nano-multilayer coatings made them good candidate protective materials in engineering applications in seawater environments.