Multiphase nanocomposite thin films composed of nanocrystalline TiN, nanosized amorphous Si3N4, and occasionally amorphous or nanocrysralline TiSi2, were deposited on high-speed steel substrate at 550 1C, using an industrial setup of pulsed-d.c. plasma-enhanced chemical vapor deposition technique. Feed gases used were TiCl4, SiCl4, N2, and H2. The composition of the films could be controlled well, through adjustment of mixing ratio of chlorides. The Si contents in films varied in the range 0-35 at%. It was found that Si contents in coatings play a great role on the quality of Ti-Si-N coatings. Ti-Si-N coatings of high Si contents were less dense than that of low Si contents. Ti-Si-N coatings with coarse grains show poor adhesion to substrates and high electrical resistance. The results indicated clearly that wear-resistant properties of TiN coating remarkably increase with addition of silicon, while friction coefficient remains high (about 0.8) at room temperature and reduces only slightly at elevated temperature (about 0.7 at 400℃). There was a much lower wear resistance in higher-Si-content films due to coarse mirostructure during formation of coating.

Superhard nanocomposite nc-TiN/a-Si3N4 coatings were prepared by reactive magnetron sputtering (RMS) and pulsed dc plasma-induced chemical vapour deposition (PCVD) on stainless steel substrates. The tribological behaviour of these coatings at room and elevated temperature was compared with that of TiN coatings deposited by RMS and PCVD. The results show that the superhard nanocomposite nc-TiN/a-Si3N4 coatings have a somewhat higher friction coefficient of 0.55-0.7 at room temperature that decreases to about 0.4-0.5 at 550 ℃. However, the friction coefficient of pure TiN coatings is 0.6 at room temperature and increases to 0.7 after a sliding distance of 0.1 km at 550℃.

The possibility of surface modification on dyes and tools is investigated with pulsed d.c. plasma enhanced chemical vapor deposition PECVD.on an industrial scale. The effects of pulsed parameters such as pulsed voltage and pulsed frequency on the performance of the coated samples are analyzed based on mechanical testing and microstructural examinations. The tested samples are titanium nitride film coated on steels and cemented carbides. Experiments indicate that the inner-wall of the holes can be coated with the aid of pulsed d.c. plasma, and the quality of coatings depends to a great extent on the pulsed parameters. The adhesion strength characterized by the critical force in indentation test can be increased over 1000N on the high-speed steel substrate when the processing condition is optimized, and the processing procedure plays an important role in the pulsing deposition.

Ti-6Al-4V alloy has been used with some success in orthopedic devices and other engineering components due to several beneficial properties. However, inadequate wear behavior of Ti-6Al-4Valloy has largely restricted fields of application for this material. In this paper, a new method of plasma nitriding and plasma-enhanced chemical vapor deposition (plasma-duplex process) was conducted on Ti-6Al-4V alloy in order to modify its wear performance. The results indicate that the plasma nitriding processing temperature plays a dominant role in nitrided layer formation when compared to other nitriding parameters (e.g. treatment time, gas flow ratio of H2/N2 etc.). It is also shown that plasma nitriding and TiN coatings produced by plasma-duplex processing provide a marked improvement in the wear performance of the modified Ti-6Al-4V alloy surface. However, the friction coefficients of plasma-duplex treated samples increased significantly compared to the substrate. There is also a negative effect on the wear behavior if the TiN coating adhesion is poor.

In order to design coatings with optimized wear and corrosion performance, knowledge of residual stress in hard coatings and its dependence on the processing parameters is required. In the present paper, TiN coatings deposited onto tool steels using pulsed d.c. plasma enhanced chemical vapor deposition were investigated. The processing parameters, including pulse voltage, pulse frequency and pre-nitriding time were varied. The residual stress was measured with X-ray diffraction and the interfacial adhesion between the coating and the substrate was evaluated using both indentation test(Pc)and scratch test(Lc). It was found that the residual stress and the adhesion could be adjusted by the processing parameters, and a correlation between these two properties was established. It was also evident that the residual stresses in coating deposited in the industrial-scale pulsed d.c. plasma CVD facility were much smaller than in those deposited in a conventional laboratory-scale chamber with d.c. power.

Pulsed direct current (dc) plasma-enhanced chemical-vapor deposition (PECVD) holds great advantages such as plasma permeation and deposition in the inner wall of holes and narrow cracks usually encountered in complex components. In this work, plasma nitriding and TiCN coatings on H13 steel have been developed using pulsed dc PECVD. The composite layer has been characterized with respect to its microhardness, adhesion, and microstructure. The results indicate that with the assistance of plasma nitriding, the composite layer improves the surface microhardness and interfacial adhesion between the coating and substrate. The application of this duplex-plasma processing on a hot-working die made of AISI H13 steel provides a significant increase in lifetime for the steel. This is a more-successful processing technique than conventional techniques, which usually do not improve the surface properties of dies, with complex shapes and demanding performance requirement conditions. However, extra hardening of this composite layer is not always advantageous. Microhardness (related to layer's strength) and adhesion, as well as the toughness of the coating system, should all be considered together.

Using direct current plasma-enhanced chemical vapor deposition (PECVD) techniques, the nanocomposite coatings of nc-TiN/a-Si3N4 11 were deposited on stainless steel substrates. The coatings were characterized by nano-indentation, elastic recoil detection spectroscopy 12 (ERD), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). The effects of 13 oxygen and chlorine were investigated in this paper. A certain content of oxygen and chlorine can strongly decrease the hardness of superhard 14 of nc-TiN/a-Si3N4. It is shown that 1-1.5 at.% of oxygen causes a decrease in hardness decrease to a value of about 30 GPa as compared to 15 45-55 GPa for a the that of below 0.2 at.% oxygen.

Multiphase nanocomposite thin films composed of nanocrystalline TiN, nano-sized amorphous Si3N4, free silicon, and occasionally amorphous or nanocrystalline TiSi2, were deposited on HSS substrate at 550 ℃ using an industrial set-up of pulsedd. c. plasma enhanced chemical vapor deposition technique. The composition of the films could be controlled well through adjustment of N2 flow rate and the mixing ratio of the chlorides. The Si contents in the films varied in a range of 0-40 at.%. The microhardness of the coatings increased firstly with increasing Si content, reached a maximum value of about Hv 5700 at the content of 13 at.% Si in the coatings, and then decreased at high Si contents.

Ti-Si-N coatings have been investigated widely in recent years due to their unique nanocomposite microstructure and attractive properties of superhardness, fairly good oxidation-resistance nearly to 1000℃, etc. In this study, Ti-Si-N coatings have been prepared by pulsed dc plasma-enhanced chemical vapor deposition in an industrial-scale chamber. Structural characterization of Ti-Si-N coatings was examined by x-ray diffraction, x-ray photoelectron spectroscopy, scanning electron micrograph, and transmission electron microscopy. The results show that: (1) The microstructure of Ti-Si-N coatings varies significantly with the processing parameters, (2) the microstructure can be confirmed as nanocomposite Ti-Si-N where nanocrystalline TiN and/or TiSi2 particles are embedded into an amorphous matrix of Si3N4, and (3) the nanocrystals have a multioriented microstructure. However, the silicon content in Ti-Si-N coatings and coating thickness as well as crystalline size all increase when the inlet gas ratio of X=[SiCl4/(TiCl4+SiCl4)]% increases. Whereas the microhardness of the coatings first increases with increased Si content, microhardness reaches a maximum value of about Hv5800 at 13 at.% Si and then decreases slightly.

In order to improve the adhesion behavior of TiN coatings deposited on H13 steel, a layered composite structure has been developed by plasma nitriding and plasma-enhanced CVD in the present studies. Effects of the nitriding process on the microstructure, adhesion and microhardness, as well as the residual stress of composite nitrided H13 TiN coatings were investigated. Experimental results showed that the adhesion of TiN coatings to substrate could be remarkably enhanced by an optimized plasma nitriding process conducted at a 25% flow ratio of N2 (H2 N2) for 1h. The formation of a new compound layer during a nitriding process at a 50% flow ratio of N2 (H2 N2) deteriorates the adhesion of TiN coatings due to premature brittle fracture between the coating and the substrate. The surface hardness of nitrided H13 TiN coatings and compressive residual stress in the diffusion interlayer increase with increasing pre-nitriding time, but the adhesion of the coatings decreases to some extent.