Study of Structural, Mechanical, and Corrosion Resistance of a Nanocomposite CrSiN/CrN/Cr Coating Deposited on AZ31: Effects of Deposition Time

Abstract

To improve the surface properties of Mg alloys and expand the applications of CrN-based materials, composite CrSiN coatings consisting of amorphous Si3N4 and nano CrN phases have been prepared on AZ31 based on the theory of fine grain strengthening and multigrain boundaries. The effect of the thickness of the coating on the structure and properties was investigated. The microstructure was studied by means of X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM). The mechanical properties, adhesion properties, and corrosion resistance were investigated using a nanoindentater, scratch testers, and electrochemical workstations. The results show that the coating consists of a face-centered cubic CrN phase, that Si3N4 is not found in the diffraction pattern, and that the HRTEM images show a composite structure of amorphous and nanocrystalline phases. With the increase in deposition time (thickness), the surface roughness decreases, the defects disappear, and the interface has no visible defects. Moreover, the hardness and elastic modulus of the coating increase, corrosion resistance improves, adhesion performance first increases and then decreases. The adhesion between coating and substrate reaches the maximum when sputtering time is 50 min, which corresponds to the CrSiN thickness of 0.79 μm.

Enhanced Wear and Corrosion Resistance of AZ91 Magnesium Alloy via Adherent Si-DLC Coating with Si-Interlayer: Impact of Biasing Voltage

“…Moreover, Table 2 shows that the I corr of the bias coating is two orders of magnitude lower than that of the AZ91 alloy. The coating biased at −300 V has the lowest corrosion rate, which is calculated by Equation ( 2) [15]. The AZ91 alloy has the highest corrosion rate at 17.77 mm/year, and the −200 V and −300 V coatings have very similar values, around 0.152 mm/year.…”

“…Figure 4a exhibits the Tafel polarization curves (TPC), which obtain polarization parameters of the coatings [5,15,16]. The electrochemical parameters are listed in Table 2.…”