Effects of deposition temperature on structure, residual stress and corrosion behavior of Cr/TiN/Ti/TiN films

Magnesium alloys are the lowest-density structural metals with a wide range of applications, such as aircraft skins, engine casings and automobile hubs. However, its low surface hardness and non-corrosion resistance in natural environments limit its wide range of applications. In this work, Si-DLC coatings (Si: 15 at.%) are fabricated on AZ91 alloy using a hollow cathode discharge combined with a DC bias voltage from 0 to −300 V to increase the deposition rate and modulate the structure and properties of the coatings. The Si interlayer with a thickness of around 0.6 µm is deposited first to enhance the adhesion. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Raman spectroscopy are used to investigate the effect of DC bias on the microstructure evolution of Si-DLC coatings. Meanwhile, corrosion and wear resistance of the coatings at various bias voltages have been investigated using electrochemical workstations and pin-on-desk wear testers. It is shown that the bias-free coating has a loose structure and is less resistant to corrosion and wear. The bias coating has a compact structure, small carbon cluster size, high chloride ion corrosion resistance, and high wear resistance against Al2O3 spheres. The corrosion potential of the coating bias at −300 V is −0.98 V, the corrosion current density is 1.35 × 10−6 A·cm−2, the friction coefficient is 0.08, and the wear rate is 10−8 orders of magnitude. The formation of SiC nanocrystals and high sp3-C, as well as the formation of transfer films on the surface of their counterparts, are the main reasons for the ultra-high wear resistance of the bias coatings. The wear rate, coefficient of friction, and corrosion rate of the coating are 0.0069 times, 0.2 times, and 0.0088 times that of the AZ91 alloy, respectively. However, the bias coating has only short to medium-term protection against the magnesium alloy and no long-term protection due to cracks caused by its high internal stress.

“…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.…”

Section: Corrosion Behaviormentioning

confidence: 99%

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

Cui,

Yang

2024

“…Titanium nitride ceramic films prepared via magnetron sputtering exhibit good corrosion [6] and wear resistance [7]. However, because of the residual stress of TiN ceramic films prepared by magnetron sputtering, spalling or failure may occur when they are stored in a service environment, which affects their normal service performance and reduces their service life [8][9][10]. The reason for this phenomenon is the significant differences in the hardness [11], coefficient of thermal expansion (CTE) [12], and lattice spacing [13] of the substrate and film, resulting in a large amount of residual stress at the interface after film preparation.…”

Section: Introductionmentioning

confidence: 99%

Influence of Interlayers on Adhesion Strength of TiN Film on Mg Alloy

Liu,

Li,

et al. 2024

The wide application of Mg alloys has been restricted because of their poor corrosion and wear resistance. Titanium nitride ceramic films prepared via magnetron sputtering can improve the corrosion and wear resistance of Mg alloys. However, residual stress produced at the interface between the film and the Mg alloy substrate causes the TiN film to spall off and reduces its service life. One potential approach to mitigating residual stress involves enhancing the adhesive strength between the film and the substrate, thereby potentially extending the service life of the film. To increase the adhesion strength between the TiN film and the Mg alloy substrate, a Ti or Al interlayer was deposited on the Mg alloy by magnetron sputtering. Subsequently, the adhesion strengths of TiN/Ti and TiN/Al were determined under a single high shear force by scratch tests and were determined under multiple low shear forces by friction and wear tests. The results of scratch tests show that TiN with the Ti interlayer on the Mg alloy substrate has superior adhesion strength under a single high shear force. And the results of friction and wear tests show that both the TiN/Al and TiN/Ti films provided protection to the Mg alloy substrate against friction and wear, and TiN with the Ti interlayer on the Mg alloy substrate has superior adhesion strength under multiple low shear forces. This work can provide guidance for the selection of interlayers between Mg alloy substrates and hard ceramic films.

“…Therefore, the surface properties of magnesium alloys need to be improved. Hard coatings which can endow Mg alloys with higher hardness, anti-corrosion, and wear resistance have been widely used to improve the surface properties of Mg alloys [1][2][3][4]. For instance, CrSiN coatings, especially nanocomposite CrSiN coatings have been used extensively in recent years.…”

Section: Introductionmentioning

confidence: 99%

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

Cui

Yang

2023

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.