| In naitoanl marine defense construction, aviation aircraft and military equipment are expected to suffer tough environment typically erosion and freeze in a long run. which may significantlly influence its usability even shorten lifetime. Inspired by lotus effect, in recent years, surface modification by means of superhydrophobic films has become an important way to promote materials performance. Superhydrophobic films can effectively inhibit surface corrosion and oxidation, and in further improve the ability of self-cleaning and anti-icing. In addition, superhydrophobic films also exhibit outstanding advantages in other fileds such as self-cleaning, transport, microfluidic devices and biomedical area. However, superhydrophobic films are supposed to meet tough service environment in actual applications. In certain fields such as aeroengine inlet cold end parts and artificial joints, superhydrophobic films are expected to be, on the one hand, anti-icing and anti-corrosion with prominent hydrophobicity, on the other hand, antifriction and wear-resistant with excellent mechanical properties. Although the traditional hydrophobic coating with polymer structure has excellent hydrophobic performance, even can exhibit self-cleaning effect, its application is limited by some factors such as low mechanical strength, poor impact resistance, as well as expensive cost. Therefore, significance of developing composite films with strong mechanical properties and excellent hydrophobicity turns out to be apparent.Nanocomposite films nowadays have attracted increasing interest due to unique nanostructure as well as outstanding mechanical properties, which can be used to overcome the problem of low mechanical strength for organic hydrophobic coatings. In addition, it should be noticed that the super-hydrophobicity come from the synergic effects of low surface energy materials and rough surface morphology. With the characteristics of low deposition temperature, low residual stress, grain refinement and macro-particle cleaning, plused bias arc ion plating (PBAIP) is suitable for deposition of nanostructure films. This paper aims to systematically investigate mechanical and hydrophobic properties of different nanocomposite hard films mainly TiN/a-C-、TiC/a-C(Cu) and TiN/Cu deposited on high speed steel (W6Mo5Cr4V2) substrates by pulsed bias arc ion plating, and furthermore, improve hydrophobic performance by means of ultrafast laser processing. Key points and results are listed as follows:1. Two-phase nanocrystalline/amorphous TiN/a-C films were successfully deposited on HSS substrates by pulsed bias arc ion plating. The deposition parameters such as bias voltage and arc current on structure and properties of the films were discussed. Applying a bias voltage of-300V in TiN/a-C films induces strong crystalline characteristic, and the film hardness and elastic modulus reach the maximum value of32.5GPa and367.4GPa. In addition, element contents vary in a wide range while adjusting arc currents and nitrogen flow rate, which obviously change phase structure and mechanical properties of the film. Based on structural analysis, TiN/a-C films show nanocomposite structure with nanocrystalline Ti(C.N) embedded in amorphous carbon matrix even if amorphous carbon takes a small amount. Hardness and friction coefficient reduce with amorphous carbon component rising. The highest hardness of37.5GPa is obtained at the level C15.6at.%and Ti45.6at.%, and the corresponding friction coefficient is around0.25. The as-deposited TiN/a-C films exhibit hydrophily with the water contact angle of80～89°, which could be attributed to high surface energy.2. A series of TiC/a-C composite films were synthesized by PBAIP using graphite and Ti targets. GIXRD reveals obvious TiC crystal phase in the film while XPS and Raman spectrum prove amorphous carbon phase either. Thanks to the increase of TiC fraction, film hardness increases from25.4to36.0GPa with Ti from38.1to49.7at.%. Compared with TiN/a-C films, the hydrophobicity of TiC/a-C films is enhanced and the highest water contact angle is102.2°. Samll amount of Cu was added into TiC/a-C films. The TiC/a-C(Cu) films show poor crystallinity and the Cu exists as metallic state in the films. The coefficient friction decreases from0.35to0.18with the increase of carbon content, while the hardness is in the range of17.6-25.2GPa. Due to the addition of Cu into TiC/a-C films, the surface energy reduces, and thus the hydrophobicity is further improved. The corresponding water contact angle of the films increases from102.7°to106.6°.3. Two-phase TiN/Cu superhard nanocomposite films were prepared by PBAIP from pure Ti and TiCu multi-component targets. Results from XRD, XPS and HRTEM indicate that the deposition films of type nc-TiN/nc-Cu exhibit nanocomposite structure with very tiny Cu nanocrystallites dispersing around the TiN crystallites. The structure of these films are strongly correlated with Cu content. A small amount of Cu can promote the growth of TiN grains, and the film shows a coarse columnar structure. With increasing in the Cu content, sufficient Cu phases are formed and resultant films are composed of equiaxed grains with random orientation. The mechanical prperties of the films are enhanced by adding trace amounts of Cu. The TiN/Cu film with0.6at.%Cu exhibits the highest hardness of40.2GPa and has good thermal stability. However, the incorporation of excess Cu causes the decrease of film hardness and elastic modulus. The hydrophobicity of TiN/Cu films is improved by adding Cu into TiN film, which is attributed to the reduction of surface energy. Water contact angle appears to be114.0°when Cu content reaches5.8at.%.4. The different square column morphology were fabricated by picosecond laser processing on the nanocomposite film surfaces. The effect of micro-nano structure on hydrophobicity of the films was investigated. It turns out that periodic square column plays a significant role in improving hydrophobic property. The water contact angles of TiN/Cu and TiN/a-C achieve the highest136.8°and130.1°while keep the width of suare column as70um, which are separately increased by32.2°and43.1°to smooth surface films. Water drops at this point appear to be Cassie state, which can be contributed to improve the ability of freezing resistance and corrosion resistance. In addition, the wear-resistant of TiN/Cu films is enhanced due to the periodic microstructure. |
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