Investigation of TiC films synthesized by low energy ion bombardment
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Low energy bombardment of CH n+ at 100-800 eV has been used to prepare TiC film at room temperature by dual ion beam sputtering. The ion bombardment energies and densities obviously affect the metallographic morphology, the crystalline orientation, and constituent ratio of TiC films. TiC films formed under 200-600 eV CH" + bombarding with 120-190 /tA/cm 2 possess much finer and compact microstructure in the compressive stress state. Its hardness is in the range of 2650-2880 kgf/mm 2 . The tribological tests indicate that TiC films synthesized on AISI 52100 steel by DIBS with low energy bombardment exhibit low friction coefficient and good wear resistance.
I. INTRODUCTION
II. EXPERIMENTAL
Titanium carbide (TiC) coating, as a refractory carbide, is of increasing interest due to its useful, and in some ways unique, physical and chemical properties. Its high hardness, good chemical inertness, and excellent resistance to wear and abrasion have rendered TiC very useful as a hard coating in industrial applications, such as to protect the surface of cutting tools from wear and erosion, extending the tool life.1'2 Dual ion beam sputtering (DIBS), based on the ion beam assisted deposition (IBAD), is currently one of the most promising techniques for preparing hard coatings. By means of ion-assisted bombardment, the films fabricated by DIBS have an excellent adhesion to substrates as a wide atomic intermixed zone is formed at the film/substrate interface. In addition, hard coatings can be deposited by DIBS on steel substrates at a low (even room) temperature, so the tempering and undesirable decarburization of steel substrate would not take place during deposition. It has been reported that a recent trend in ion beam metallurgy is to apply the ion-assisted bombardment to improve the properties of hard coatings in depositions.3"6 However, the bombarding energy used for synthesizing TiC film is usually much higher than 1 keV.3'5 To our knowledge, the effects of low energy ( < 1 keV) ion bombardment on the film formation and its implications for properties are rarely reported. In this article, we mainly investigated the effects of low energy ion bombardment in the DIBS process on the characteristics of TiC films, such as the preferred crystallization, the surface morphology, and the constituent ratio of TiC film. In addition, the microhardness measurements and some tribological tests were carried out to evaluate the properties of obtained TiC films.
Silicon (111) wafer and AISI 52100 steel (HRC 61) were used as substrates for deposition. TiC films were synthesized by using a multifunctional ion beam assisted deposition system. The vacuum chamber for film deposition, shown in Fig. 1, is mainly equipped with three broad-beam ion sources, one rotatable watercooled sample holder, and one rotatable water-cooled target holder. Detailed operating parameters are described in Ref. 7. In experiments, the base pressure of the chamber was below 3 X 10~6 Torr, and the working pressure (including methane partial pressure of about 8 X 10"
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