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Diamondlike carbon (DLC) films are deposited on AISI 304 stainless-steel substrates using hollow-cathode chemical vapor deposition. The effects of the substrate bias on the structural and mechanical properties of the films are studied. X-ray photoelectron spectroscopy reveals the existence of CC (sp2) and C–C (sp3) functional groups in the films, and Raman spectra show that the ratio of the G (graphite) peak to the D (disorder) peak depends on the sample bias. The DLC film deposited at −50V bias has the highest sp3 content, and this is consistent with the G-band position and D-band full width at half maximum as a result of substrate biasing. The sample bias also has a critical influence on the thickness and hardness of the deposited films. The largest thickness (1700nm) and highest hardness (HV1099) are achieved at a bias voltage of −50V. All the films show low friction coefficients, and the sample treated at −200V gives rise to the lowest friction coefficient.

Amorphous hydrogenated carbon (a-C:H) films have been deposited on polyethylene terephthalate by plasma immersion ion implantation and deposition. The influence of deposition parameters such as gas pressure, bias voltage, and nitrogen incorporation on the mechanical properties of the a-C:H films are investigated. X-ray photoelectron spectroscopy reveals that the ratio of sp3 to sp2 is 0.24 indicating that the film is mainly composed of graphitelike carbon. Nanoindentation tests disclose enhanced surface hardness of ∼6GPa. The friction coefficient of the film deposited at higher gas pressure, for instance, 2.0Pa, is lower than that of the film deposited at a lower pressure such as 0.5Pa. The films deposited using a low bias voltage tend to fail easily in the friction tests and nitrogen incorporation into the a-C:H films decreases the friction coefficient. Mechanical folding tests show that deformation failure is worse on a thinner a-C:H film.

Titanium nitride (TiN) films have been deposited on AISI 304 stainless steel substrates using hollow cathode reactive plasma vapor deposition. Titanium is introduced by sputtering the Ti cathode nozzle and TiN is formed in the presence of a nitrogen plasma excited by radio frequency. The substrate bias voltage is varied from 0to−300V to investigate its effect on the mechanical and structural properties of the films. X-ray diffraction results show the formation of TiN (111) and Ti2N (220) phases in the films. The sample bias has a critical influence on the thickness of the deposited films. The bias of −200V leads to the thickest films (about 1680nm) and the deposition rate is 18.7nm∕min. The microhardness, root-mean-square (rms) roughness values, and tribological properties also exhibit nonlinear relationship with increasing bias voltages. The highest hardness of about 1027 hardness vickers and best wear resistance are achieved at a bias voltage of −100V. Atomic force microscopy results reveal the lowest r...

Degradable metal alloys constitute a new class of materials for load-bearing biomedical implants. Owing to their good mechanical properties and biocompatibility, magnesium alloys are promising in degradable prosthetic implants. The objective of this study is to improve the corrosion behavior of surgical AZ91 magnesium alloy by titanium ion implantation. The surface characteristics of the ion implanted layer in the magnesium alloys are examined. The authors’ results disclose that an intermixed layer is produced and the surface oxidized films are mainly composed of titanium oxide with a lesser amount of magnesium oxide. X-ray photoelectron spectroscopy reveals that the oxide has three layers. The outer layer which is 10nm thick is mainly composed of MgO and TiO2 with some Mg(OH)2. The middle layer that is 50nm thick comprises predominantly TiO2 and MgO with minor contributions from MgAl2O4 and TiO. The third layer from the surface is rich in metallic Mg, Ti, Al, and Ti3Al. The effects of Ti ion implantation...

Plasma immersion ion implantation (PIII) is an effective materials modification and synthesis technique but has seldom been applied to ceramic materials due to the high electrical resistance that reduces the ion bombardment energy and sometimes causes serious electrical arcing in the instrument. Even in cases where PIII is applicable, the surface properties of the implanted insulating materials can be seriously affected due to the low ion energy and materials damage from electrical arcing. In order to enhance the surface and mechanical properties such as wear resistance of ceramic materials used in many industrial applications, surface modification is needed. In this work, we conduct carbon implantation into sintered α-SiC (silicon carbides that are widely used in vacuum ceramic bearings) using mesh-assisted plasma immersion ion implantation to enhance the surface properties. The use of a conducting grid is necessitated by the high electrical resistance that induces a large voltage drop across the substra...

Plasma immersion ion implantation and deposition (PIII–D) offers a non-line-of-sight fabrication method for various types of thin films on steels to improve the surface properties. In this work, titanium films were first deposited on 9Cr18 (AISI440) stainless bearing steel by metal plasma immersion ion implantation and deposition (MePIII–D) using a titanium vacuum arc plasma source. Afterwards, carbon implantation and carbon film deposition were performed by acetylene (C2H2) plasma immersion ion implantation. Multiple-layered structures with superior properties were produced by conducting Ti MePIII–D + C2H2 PIII successively. The composition and structure of the films were investigated employing Auger electron spectroscopy and Raman spectroscopy. It is shown that the mixing for Ti and C atoms is much better when the target bias is higher during Ti MePIII–D. A top diamond-like carbon layer and a titanium oxycarbide layer are formed on the 9Cr18 steel surface. The wear test results indicate that this dual P...

Dynamic plasma-based thin-film deposition incorporating ion mixing and plasma immersion is an effective technique to synthesize nitride-based hard films. We have fabricated TiN films using a filtered titanium vacuum arc in a nitrogen plasma environment. A pulsed high voltage is applied to the target for a short time when the metallic arc is fired to attain simultaneous plasma deposition and ion mixing. We investigate the dependence of the corrosion resistance and interfacial structure of the treated samples on the applied voltage. Our Auger results reveal an oxygen-rich surface film due to the non-ultra-high-vacuum conditions and high affinity of oxygen to titanium. The corrosion current is reduced by two orders of magnitude comparing the sample processed at 8 kV to the untreated sample, but the 23 kV sample unexpectedly shows worse results. The pitting potential diminishes substantially although the corrosion current is similar to that observed in the 8 kV sample. The polarization test data are consistent with our scanning electron microscopy observation, corroborating the difference in the pitting distribution and appearance. This anomalous behavior is believed to be due to the change in the chemical composition as a result of high-energy ion bombardment.

Compared to conventional direct current magnetron sputtering, high power impulse magnetron sputtering (HiPIMS) gives rise to higher plasma activity which can be exploited to deposit films with the preferred microstructure and higher critical load, but in practice, most of the electrons are not effectively utilized and lost to the anode (chamber wall). In order to achieve higher ion flux to substrate and denser microstructure of the films, an external magnetic field is introduced. In our HiPIMS system, a coil around the magnetron target induces larger enhancement effects, and the substrate current can be increased by a factor of 2 or more if the proper current flows through the coil to intensify and confine the glow discharge. The magnetic-field-enhanced HiPIMS technology is adopted to produce (AlTi)xN1-x films with smooth surfaces and better mechanical properties such as surface hardness and a larger coil current produces films with lower friction. The improvement is attributed to enhanced glow discharge,...

Elevated-temperature plasma immersion ion implantation can be used to improve the surface properties of austenite stainless steels. Unlike previous investigations conducted using radio frequency plasma at a moderate gas pressure (0.1–0.5 Pa), we recently conducted a series of experiments at lower pressure (∼0.06 Pa) utilizing nitrogen plasma sustained by hot filament glow discharge. The implantation voltage was varied from 8 to 25 kV and the sample temperature was kept at 360 °C by adjusting the implantation current density. To elucidate the mechanism and dynamics of the process, the treated samples were characterized by Auger electron spectroscopy and Rutherford backscattering spectrometry. Our experimental results show that surface oxidation is very severe at lower pressure due to higher oxygen partial pressure. It affects the nitrogen profile and diffusion. Since typical plasma immersion ion implanters are not designed for ultrahigh vacuum, the presence of the oxygen in the residual vacuum can give ris...

A surface layer consisting of titanium, nitrogen, and oxygen is implanted/deposited onto SS304 stainless steel using dynamic mixing and plasma immersion ion implantation. Titanium is introduced into a nitrogen glow discharge plasma from a metal arc plasma source. Dynamic mixing is achieved via the co-implantation of Ti ions with high charge states as well as nitrogen and oxygen ions in the plasma. The resulting surface layer possesses superior tribological properties and corrosion resistance. The observed improvement in the wear resistance is more than a factor of 10. The enhancement in the surface properties is believed to be due to the synergistic effects of the coexistence and dynamic mixing of titanium, nitrogen, and oxygen at the interface.

Dual plasma deposition based on plasma immersion ion implantation and plasma deposition is a fledgling technique for the fabrication of functional thin films. One of its advantages is the easy adjustment of the ion kinetic energy during the process. It is straightforward to control the ion kinetic energy during the fabrication of conducting thin films on conducting substrates by simply varying the negative dc voltage applied to the targets. However, for the fabrication of insulating thin films or film deposition on insulating substrates, charge accumulation makes it difficult for ions to attain the proper kinetic energy. In these cases, a pulse or ac voltage is commonly employed. In this article, we theoretically investigate the process window in dual plasma deposition with respect to the pulse width and frequency of the applied voltage to avoid electrical breakdown of the film as well as large ion kinetic energy deviation. The model can deal with the deposition of insulating thin films on conducting or i...

Plasma immersion ion implantation is a nonline-of-sight method for fabricating amorphous carbon or diamond-like-carbon coatings on steels to improve the surface properties. In this work, carbon thin films are synthesized on 9Crl8 (AISI440) stainless bearing steel by acetylene (C2H2) plasma immersion ion implantation (PIII). The effects of the processing parameters, including rf power, sample voltage pulse duty cycle, and target bias, on the structure and surface properties of the carbon thin films is systematically investigated employing Raman spectroscopy, Auger electron spectroscopy, friction coefficient measurement, and wear test. The results reveal that carbon films several hundred nanometers thick with a well-mixed interface are formed on the 9Crl8 steel after C2H2 PIII, but the structure and properties of the carbon films vary greatly under different PIII conditions. There is an optimal process window within which the synthesized films have superior properties, and current densities that are too hig...