Papers by Keyword: Unbalanced Magnetron Sputtering

Abstract: In view of the present reality of sputtered plating bearings imported in our country, unbalanced magnetron sputtering deposition techniques was used to fabricate AlSn20 anti-friction coating on aluminum bearing alloy. Microstructure characterization of the coating was performed by SEM. Micro-hardness testing of Coating were measured with a Vickers indenter. Adhesion testing was carried out with a scratch tester. Wear and friction tests were performed with a pin-on-disc tribometer. The results revealed that the AlSn20 anti-friction coating (bias voltage in the range of-60V~-100V) showed finer crystal, better corrosion resistance (E_corr=-1.25V), higher hardness (up to 80HV0.025), better adhesion with substrate (up to 35N), and lower friction coefficients down to 0.15.

Abstract: In order to improve the cell biocompatibility of pure iron surface as cardio-vascular stent material, Fe-O film was deposited on single crystal silicon by unbalanced magnetron sputtering. Human umbilical vein endothelial cells were seeded on the 316L SS, pure iron and Fe-O film surface, whereafter cultured in vitro. Adhesion behavior was detected after 2 h incubation. Cell morphology and proliferation activities were assessed at 1, 3 and 5 days. The results show that the endothelial cells are easy to adhere and spread on the surface of Fe-O film. Compared with 316L SS samples, the cells count and area coverage of Fe-O film in 1 and 5 days make a difference significantly. These results demonstrated that the Fe-O film prepared by unbalanced magnetron sputtering technique has good cytocompatibility.

Abstract: Graphite-like carbon films were deposited on DC53 steel substrate by unbalanced magnetron sputtering. The microstructures of the resultant films were investigated by Raman spectroscopy, scanning electron microscope (SEM), energy dispersive spectrometer (EDS) and X-ray diffractometer (XRD), respectively. Ball-on-disc tribometer was employed to analyze the tribological properties of the film. The results show that the films were dominated by sp² sites. The surfaces are uniform and dense, the sectional morphology of the films present dense columnar crystal. The films have superior tribological properties under different loads, including low friction coefficient (0.18-0.33) and low wear rate (2.53×10^-17m³/(Nm)- 8.47×10^-17m³/(Nm)).

Abstract: As the trend of electronic industry is fast moving towards miniaturization, diversity, high efficiency and high throughput, the devices to be mounted onto a PCB are increasingly densely packed so are the holes needed to keep all elements in place. To effectively and economically generate so many holes of small diameter and high aspect ratio, the drilling process has to be done in a high speed manner and tool life has to be kept as long as possible. This study aimed to improve the tool life and the quality of the obtained holes by applying various hard coatings on the drills. The results showed that tool life could be effectively improved from 2500 hits to around 11000 hits at 155Krpm and 3.5m/min when proper hard coating was applied. It was found that wear of drill was resulted mainly from abrasive wear and adhesion wear. It was also showed in the research that while non-coated drills suffered serious deformation after 500 hits those coated with Al2O3 could finish 11000 hits with very limited wear land on the drills.

Abstract: This paper reports the effects of varying magnetic field strength on CrN films, deposited by a magnetic sputtering process. The strength of magnetic field in unbalanced magnetic sputtering processes is controlled by adjusting the gap distance between the magnet set and the target surface (GDMT). An improvement in overall intensity, at low GDMT, was observed by adjustable magnetic field distributions. In the chamber, it was readily noticeable that varying the magnetic field strength has an influence on the CrN structures. In experiments, at low GDMT, a high hardness value and lower wear rate become visible in the CrN films. In addition, the CrN films formed have a smooth surface with a dense tiny structure and display preferential orientation in the Cr2N(111) and Cr2N(002) planes, whereas CrN films prepared at higher GDMT exhibit more roughness and the CrN (200) plane is evident. Furthermore, the Cr2N (111) (002) plane possessed better tribological properties than that of the CrN(200) plane, where the wear scars show little failures on the coating surface.

Abstract: This paper presents the optimal chromium nitride (CrN) deposited performance by tuning magnetic systems on die steel in PVD. The strength of magnetic fields was controlled by adjusting the gap distance between magnet sets and target surfaces of the unbalanced magnetic field of sputtering systems. In L18 orthogonal experiments, the effect of control factors were explored such as gap distance between magnet set and target surface (GDMT), target current, argon and nitrogen flow rate, DC pulse frequency, and work distance. Hardness and wear behavior of the CrN films were analyzed using a statistical method. The wear rate was estimated by Pappus’s theorem. Among the results, the Cr2N phase with the mixture crystallographic orientations of (111) and (002) exhibited better wear resistance than CrN(200) with a single preferential orientation. In addition, variance analysis exhibited the largest percentage contribution to friction coefficient in comparison with the other two properties of friction coefficient and GDMT, which showed that GDMT is extremely sensitive to friction coefficient.

Abstract: Quaternary CrTiAlN hard coatings were deposited by closed field unbalanced magnetron sputtering ion plating technique onto steel substrates, and their structural, mechanical, and tribological properties after heat treatment in air at different temperatures (500-900 oC) were studied and compared by means of scanning electron microscopy (SEM), X-ray diffraction (XRD), micro-indentation, and pin-on-disc (POD) tribometer, etc. The onset temperature of oxidation was determined by thermogravimetric analyser (TGA). The compositional depth profiles before and after the heat treatments were examined by X-ray photoelectron spectroscopy (XPS) in order to study the oxidation mechanism. The experimental results indicate that the CrTiAlN coatings have excellent oxidation resistance and thermal stability, and outperform the traditional hard coatings like TiN and TiAlN in terms of higher oxidation temperature, hardness, adhesion, and wear resistance. It is expected that the CrTiAlN coatings with superior properties should have better performance in dry high speed machining.

Abstract: Ti-doped diamond-like carbon(Ti-DLC) coatings and undoped diamond-like carbon(DLC) coatings were synthesized by unbalanced magnetron sputtering using carburized Chromium Molybdenum Steels (SCM415) as substrates. Nanocomposite structure coatings with metal carbides nanocrystals uniformly dispersing in the amorphous carbon matrix were obtained by the optimization of the kinds of doped metals and deposited parameters. This kind of nanocomposite structure permits improved hardness while maintaining a lower residual stress and getting thick coatings. The friction coefficients of Ti doping DLC coatings are relatively lower compared with undoping DLC coatings in engine oil. The analysis on the wear surface of coatings have indicated that: the surface of DLC doped with metal absorbs more elements from the engine oil, which indicates that the doping of metal can improve the affinity of the coating for the engine oil, enhance the formation of lubrication oil films, and reduce the friction coefficient thereby.

Abstract: Si-N-O films have drawn researcher’s much attention recently due to their potential superiority in blood compatibility of biomaterials. In this paper, Si-N-O films were synthesized on <100> silicon substrates by pulsed reactive unbalanced magnetron sputtering a single crystal silicon target with high purity in a mixture atmosphere of Ar and N2. XPS and FTIR results showed the Si-N-O films synthesized at higher N2 flux could be described to random bonding model (RBM). In RBM, the Si2p existed in the form of a-Si3N4 and SiNνO4-ν (ν=0,1,2,3,4) components. Platelet adhesion behavior on Si-N-O films was assessed by platelet adhesion test and Lactate dehydrogenase (LDH) assay, qualitatively and quantitatively separately. The correlativity of film chemical structure and blood compatibility was investigated. The results of platelet adhesion and activation showed that the RBM film with higher N/O ratio exhibited favorable blood compatibility. It was shown that the Si-N-O film with specific composition and chemical bonding state was superior in blood compatibility compared to low temperature isotropic carbon (LTIC).

Abstract: The magnetic filed arrangement of unbalance magnetron sputtering can be changed employed to expand the plasma region and induce more ions to bombard the films for fabricating excellent quality films. In this paper, four targets closed-filed unbalance magnetron sputtering was introduced, the effect of the different magnetic field arrangement on the titanium oxide films properties was investigated. By changing the distance from target to vacuum center, the different unbalance state of the magnetic field was formed around the substrate. The titanium oxide films were synthesized at different unbalance state of the magnetic field. The microstructure of the titanium oxide films was studied by X-Ray Diffraction (XRD), and the residual stress measurement for the films was determined by grazing incidence XRD. The results revealed that the higher unbalance of the magnetic field around the substrate, the higher ion current of the substrate. Comparing with increasing the substrate bias voltage, the ion current increased 2~4 times through changing magnetic field arrangement to induce higher unbalance of the magnetic field. Ion/atom ratio increase was in favor of rutile phase formation for titanium oxide film. The unbalance state increase resulted in more higher compressive stress in the films.