Atsushi Mitsuo

Friction and wear properties of CrAlN and CrVN films deposited by cathodic arc ion plating method

Abstract Chromium nitride (CrN) films are superior to the titanium nitride film in corrosion and wear resistances, and friction behavior. CrN has been widely applied to the molding dies, machine parts and sliding part. In the present paper, additions of aluminum and vanadium into CrN films were performed with an expectation of improvement in tribological properties. CrN, CrAlN and CrVN were deposited by a cathodic arc ion plating. Deposited films were characterized by X-ray diffraction for crystal structure identification and energy-dispersive X-ray spectroscopy for chemical composition analysis. Diffraction peaks that appeared were similar in position and orientation in all films because the crystal structure and the lattice constant for CrN, VN and AlN are close to each other. The composition of the film deposited with Al and V was estimated to be Cr70Al30N and Cr50V50N, respectively. Knoop hardness test showed that CrAlN was harder than CrN and CrVN. Friction and wear tests were carried out by a ball-on-disk tribometer with stainless steel and cemented carbide balls as a counter material, with and without lubricant. Flaking occurred on CrN with stainless steel ball in wear tests without lubrication by ball-on-disk tribometer, but that did not occur on CrAlN and CrVN films. In the case of the wear test with cemented carbide ball, depth of wear track on CrN film reached to the substrate. The friction coefficient was almost the same for CrN and CrAlN films; however, that for CrVN film was lower than other films, in motor oil. V addition into CrN film successfully improved its tribological properties.

Effect of aluminum concentration on friction and wear properties of titanium aluminum nitride films

Abstract It is well known that the hard thin ceramic films are utilized to industrial applications such as cutting tools, molding dies and sliding parts, because of its effect of reducing the wear. Recently, the demand of TiAlN film is expanding, because it has a high oxidation resistance at elevated temperature as well as good wear resistance. In this paper, friction and wear properties of TiAlN films having various concentration ratios of Ti/Al have been studied. The films were deposited by a cathodic arc ion plating method on cemented carbide substrate with a thickness of approximately 3 μm. Composition of the deposited film was evaluated by energy dispersive X-ray spectroscopy. Crystal structure of the deposited film was characterized by X-ray diffraction. Hardness of the films was measured by a nano-indentation tester. Friction and wear tests were carried out by a pin-on-disk tribometer at 300, 473, 673 and 873 K. Compositions of the films deposited from cathode materials that have atomic ratios (Ti:Al) of 50:50, 34:66 and 25:75 in TiAl alloys were Ti 0.6 Al 0.4 N, Ti 0.42 Al 0.58 N and Ti 0.3 Al 0.7 N, respectively. The crystal structure of Ti 0.6 Al 0.4 N Ti 0.42 Al 0.58 N and Ti 0.3 Al 0.7 N were found to be a B1, B4+B1 and B4, respectively. Nano-hardness decreased with increasing Al content in the films. There is no correlation between friction coefficient of each film and test temperature. The width of wear track for each film decreased above the temperature of 673 K. Ti 0.6 Al 0.4 N film was worn less than the other films at 873 K.

Self-lubrication mechanism of chlorine implanted TiN coatings

Different from the conventional physical modifications, significant reduction of wear and friction in severe dry conditions can be accommodated to titanium nitride (TiN) coating via the chlorine ion implantation. High friction coefficient with μ=0.8–1.2 for the as-deposited TiN is reduced to be less than 0.2 at room temperature. Titanium mono-oxide (TiO) and oxides with oxygen deficiency or Magneli phase with TinO2n−1, were formed inside the wear track of Cl-implanted TiN coating. Due to the shear deformability of titanium mono-oxide and crystallographic shearing planes in this Magneli phase, vicinity of the Cl-implanted TiN surface can be elasto-plastically deformed, resulting in reduction of shear stress, wear and friction. Micro-X-ray photoelectron spectroscopy (XPS) measurement as well as high-resolution transparent electron microscopy (HRTEM), were an effective tool to describe local surface reaction taking place inside and outside of the wear track. Oxidation process of TiN during wear is drastically changed at the presence of Cl-atoms on the surface. Cl-atoms diffuse from the inside of TiN to the surface to accelerate the formation of titanium oxides, and to escape out of the system together with oxide debris. Both wear volume and friction coefficient, are preserved to be as low as or lower than diamond like carbon (DLC) coatings. This preferable tribological property comes from self-lubrication mechanism of the Cl-implanted TiN due to significant change of surface reaction by the effect of Cl-atoms.

Mechanical properties of zirconium films prepared by ion-beam assisted deposition

Abstract Zirconium nitride films were prepared by ion-beam assisted deposition on single-crystal silicon substrates. The films were synthesized by depositing the zirconium vapor from an electron-beam source, under the irradiation of nitrogen ions from an arc ion source. Transport ratio of Zr to N was varied from 1.0 to 3.0 by controlling the deposition rate of Zr. The ion beam density was kept constant, 0.2 mA/cm 2 . The ion beam energy was varied between 0.5 and 2.0 keV. The films were characterized by X-ray diffraction (XRD) and Auger electron spectroscopy. Hardness of the films was measured by the nano-indentation tester. The tribological behavior of films was evaluated by the ball-and-disk tribometer, under the normal load of 2 N and the relative sliding speed of 10 mm/s. The steel balls were used as a counter material. Formation of ZrN was recognized in XRD pattern for all deposition conditions. Depth profiles measured by X-ray photoelectron spectroscopy showed that the composition ratio of Zr to N was uniform in the inside of film. The hardness of the films increased with decreasing the transport ratio. Tribological properties of films are also discussed.

Friction and wear properties of carbon-ion implanted titanium nitride films

Abstract TiN films were deposited by ion plating on high speed tool steel substrates, and implanted by carbon ions with fluences up to 5×10 17 ions/cm 2 and with energies ranging from 50 to 150 keV. Friction and wear tests were carried out by a pin-on-disk tribometer with stainless steel balls as a counter material. The surface layers of TiN films modified by the carbon-ion implantation were characterized by X-ray diffraction (XRD) for crystal structure identification and X-ray photoelectron spectroscopy (XPS) for chemical composition analysis. The carbon-ion implantation reduced the friction coefficient of the TiN films against the stainless steel balls, and also the wear volume of the steel balls. The duration of the low friction coefficient was extended with increasing carbon dose. Adhesion of the counter material could be prevented by the carbon-ion implantation into TiN film, leading to a drastic decrease of the friction coefficient. The tribological properties of the carbon-implanted TiN films can be controlled by carbon dose and ion energy: wear rate and frictional behavior of the TiN coating can be reduced.

Feasibility study of self-lubrication by chlorine implantation

Implantation of chlorine into titanium nitride (TiN) coating on the high-speed steel substrate has succeeded in significant reduction of wear rate and friction coefficient for original TiN under dry wear condition. Through precise investigation on the surface reaction in the wear track, in situ formation of oxygen-deficient titanium oxides was found to play a role as a lubricious oxide. In the present paper, this self-lubrication mechanism is further investigated for various wearing conditions. For wide range of sliding speed and normal load in the wear map, the wear volume of a counter material is actually reduced with comparison to the un-implanted TiN. Effect of the ion implantation dose on this self-lubrication mechanism is also studied for practical use. Some comments are made on further application of this self-lubrication to manufacturing.

Self-lubrication of nitride ceramic coating by the chlorine ion implantation

Abstract Various kinds of ceramic nitride coatings are widely utilized as a protective or tribological film for cutting tools or metal forming dies. Although most of them have a potential to reduce the wear rate of steel, aluminum or titanium alloy parts, further improvement of oxidation resistance and wear toughness with less use of lubricants is still needed to meet the severe wearing conditions required by the coming automotive parts. Dry forming and dry machining has become a promising green, environmentally benign manufacturing process. In addition to diamond-like carbon or MoS2 coatings, the tribological film via the self-lubrication process is also a useful approach to attain low wear and friction state. In the present paper, ideal tribo-film can be accommodated by the chlorine implantation to titanium nitride (TiN) films. No physical change occurred for surface roughness and lattice structure of TiN. In the presence of chlorine, the vicinity of TiN coating surface is oxidized to significantly reduce the surface hardness. Since the elasto-plastically deforming Magneli phase is in situ formed during wearing, both friction coefficient and wear volume are reduced all through the life of original TiN coating. Through this experimental demonstration of practical usefulness, the further research and development toward dry forming and dry machining is discussed.

Effect of chlorine distribution profiles on tribological properties for chlorine-implanted titanium nitride films

Abstract The tribological properties of chlorine-implanted TiN films prepared on high-speed tool steel were investigated. Chlorine ion implantation up to 1×10 17 ions/cm 2 was performed at energy ranging from 33 to 100 keV. Friction and wear tests were carried out using a pin-on-disk tribometer with steel balls as the counter material. The modified surface layers were characterized by X-ray diffractometry (XRD) and transmission electron microscopy (TEM) for crystal structure identification, and by glow-discharge optical emission spectrometry (GD-OES) for chemical composition analysis. Auger electron spectroscopy (AES) was also utilized for composition analysis of the wear debris. The chlorine ion implantation reduced the friction coefficient of the TiN films from 1.1 to less than 0.2 against the stainless steel balls. The wear volume of the stainless steel balls was also reduced. We suggest that adhesion of the counter material has been prevented in the wear track by the chlorine ion implantation. The tribological behavior of TiN film is related to the distribution of the implanted chlorine atoms. In the case of the low implantation energy, the low dose of chlorine was enough to improve the tribological properties of the TiN film in the initial stages of testing. This is because the implanted chlorine atoms have been distributed close to the surface of the TiN film in a manner dependent on the implantation energy.

Effect of aluminum ion implantation on high temperature oxidation of nickel-based alloys

Abstract The thermal oxidation properties of Al-ion-implanted, Ni-based alloys used for thermocouples of Inconel 600, alumel, chromel and constantan have been studied in humid O 2 atmospheres at 970 K for 50 h. The Al ion implantation was performed with doses ranging from 1 × 10 16 to 2 × 10 17 ion cm -2 at an energy of 50 keV. The depth profiles measured by Auger electron spectroscopy showed that the concentrations of Al and O were higher near the surface of the alloys after implantation. The implanted alumel and constantan exhibited no effect on the suppression of oxidation. However, implantation above a dose of 1 × 10 17 Al ion cm -2 significantly slowed the oxidation of the Inconel 600 and chromel alloys containing Cr. The thermoelectric properties of the actual thermocouples modified by Al ion implantation are discussed.

Thermal oxidation and characterization for surface layers of Al implanted TiN films

Thermal oxidation behavior of aluminum ion implanted titanium nitride films have been studied in dry oxygen atmosphere. TiN films of approximately 2 /spl mu/m in thickness were prepared on 18-8 stainless steel (corresponding to AISI 304) substrates by a hollow cathode discharge ion plating. Aluminum ion implantation was performed at energies of 50 and 100 keV with the doses up to 4.5/spl times/10/sup 17/ ions/cm/sup 2/. Continuous oxidation tests were carried out of TiN films implanted with Al, and oxidation inhibition was evaluated from their mass gain. The structure of the surface layers was characterized by X-ray diffractometer (XRD). X-ray photoelectron spectroscopy (XPS) was used to analyze the chemical bonding states of elements in surface layers of films. The oxidized surfaces of as-deposited TiN films have rutile TiO/sub 2/ above the temperature of 873 K. However, Al implantation caused the oxidation rate of TiN films to slow down at the initial stage of oxidation. In the case of TiN films implanted with 3/spl times/10/sup 17/ Al/cm/sup 2/ and oxidized at 1073 K for 2 hours, the Al/sub 2p/ XPS spectrum reveals oxide states as Al/sub 2/O/sub 3/, although no oxides were found on XRD patterns. The Al oxides formed on the Al implanted TiN films are considered to improve the oxidation of these films. The initial oxidation behaviors of the Al implanted TiN films are similar to that of TiAlN films deposited by a cathodic are ion plating.