Diamond-like carbon (DLC) film is widely used due to its excellent properties, such as high hardness and high wear resistance. To investigate the advantages of DLC film applied on the surface of Mg alloy, direct current (DC) pulse magnetron sputtering was used to prepare DLC film via plasma sputtering a graphite target and introducing C₂H₂ gas. The silicon interlayer was fabricated by sputtering the Si target. A scanning electron microscope (SEM), transmission electron microscope (TEM), a nano-indentation instrument, an electrochemical workstation and a pin-on-disc tester were employed to obtain the surface morphology, microstructure, mechanical properties, corrosion behavior and wear resistance of the obtained film, respectively. The results show that the DLC films are dense and compact, and the structure changes from amorphous to nanocrystalline with the increase of C₂H₂ flow. The film prepared at low C₂H₂ flow has larger surface roughness, lower deposition rate, higher hardness and elasticity modulus, poorer corrosion resistance and better wear resistance, compared with the film prepared at higher acetylene flow. The self-corrosion potential of the obtained DLC film is higher than −0.95 V, the corrosion current density is 10⁻⁷ A/cm² orders of magnitude, and the wear rate is 10⁻⁹ mm³/Nm orders of magnitude. The friction coefficient of the film is less than 0.065, the hardness is 17.3 to 22.1 MPa, and the elastic modulus is 145 to 170 MPa. The DLC films obtained on the surface of AZ91 alloy have good comprehensive properties.

To increase the service life of tool materials and further meet the demands of modern high-speed machining, a Si-doping CrN coating consisting of Si₃N₄ amorphous and CrN nanocrystalline was fabricated on top of W18Cr4V high-speed steel. The effect of coating thickness on its structure and properties was investigated by means of X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), scratch test, nano-indenter, and friction–abrasion tester. The thickness of the coating was modulated by the deposition time. The results show that the coating consists of a CrN phase distributed into an amorphous Si₃N₄ matrix. As the thickness increased, the surface defects decreased, and the residual compressive stress, hardness, and elastic modulus as well as the H/E and H³/E² factors increased, improving the wear resistance significantly. The adhesion between coating and substrate increased first and then decreased, and it reached the maximum when the coating thickness was 1.9 μm (deposition 60 min). Moreover, the effect of toughness on wear resistance and the wear mechanisms is discussed.

Composite titanium carbonitride (TiCN) thin films deposited on AZ31 by DC/RF magnetron sputtering were vacuum annealed at different temperatures. Vacuum annealing yields the following on the structure and properties of the films: the grain grows and the roughness increases with an increase of annealing temperature, the structure changes from polycrystalline to single crystal, and the distribution of each element becomes more uniform. The residual stress effectively decreases compared to the as-deposited film, and their corrosion resistance is much improved owing to the change of structure and fusion of surface defects, whereas the wear-resistance is degraded due to the grain growth and the increase of surface roughness under a certain temperature.