Microstructure and properties of nitrogen ion implantation/AlN/CrAlN/MoS2-phenolic resin duplex coatings on magnesium alloys

Abstract

The novel nitrogen ion implantation/AlN/CrAlN/MoS2-phenolic resin duplex coatings are fabricated on the AM60 magnesium alloys. The microstructure, tribological and electrochemical properties of the duplex coatings are characterized by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, nano-indenter, electrochemical corrosion and wear tester. These studies reveal that the MoS2-phenolic resin coating has a two-phase microstructure crystalline MoS2 particles embedded in the amorphous phenolic resin matrix. The single-layer MoS2-phenolic resin enhances the corrosion resistance of magnesium alloys, but shows poor wear resistance due to the low substrate's load bearing capacity. The addition of nitrogen ion implantation/AlN/CrAlN interlayer in the MoS2-phenolic resin/substrate system greatly enhances the substrate's load bearing capacity. The AlN/CrAlN/MoS2-phenolic resin duplex coating with a high load bearing capacity demonstrates super wear resistance (i.e., long wear life and low friction coefficient). In addition, the nitrogen ion implantation/AlN interlayer greatly depresses the effect of galvanic corrosion because its potential is close to that of the magnesium alloys, but the nitrogen ion implantation/AlN/CrAlN interlayer is inefficient in reducing the galvanic corrosion due to the large potential difference between the CrN phase and the substrate. As a result, the nitrogen ion implantation/AlN/MoS2-phenolic resin duplex coating shows a better corrosion resistance compared to the nitrogen ion implantation/AlN/CrAlN/MoS2-phenolic resin.