S.A. Plotnikov

The effect of substrate and DLC morphology on the tribological properties coating

Abstract We studied the effect of the initial substrate surface roughness and as grown DLC microrelief on the tribological properties of coating. The diamond-like films were prepared by pulse arc sputtering of graphite onto R6M5 and 20Cr13 tool steel substrates. Special attention was paid to production of the DLC having increased the friction coefficients necessary for such device as printing machine valves and chuck’s jaws. The tribological properties of the deposited coatings were studied under conditions of dry sliding friction and under the action of an abrasive-particle jet. It was shown using both testing methods that the substrate surface roughness (R) is the decisive parameter for the wear resistance of the DLC to external loads. The wear resistance of coating is increased several-fold at some optimal R-value as compared to the smoother surface. The optimal R-value depends on the coating thickness, h. The optimal R/h value should not deviate largely from the ratio R/h∼0.2–0.3.

Effect of adhesion strength of DLC to steel on the coating erosion mechanism

Abstract The wear of DLCs deposited onto steel substrates using a graphite arc-pulse sputtering technique in a corundum particle jet was studied. Two sample sets had different adhesion strength to the substrate due to different adhesive sublayer structures. It was found that the DLC itself does not wear, so that coating destruction occurs due to peeling. Analysis of the wear results for coatings having different (0.4–2.6 μm) thickness revealed that peeling is a result of two basic crack systems: (i) from the DLC surface inside the coating; and (ii) along the DLC–substrate interface.

The effect of additional treatment on tribological properties of amorphous carbon coatings on metals

Abstract We have developed the effect of additional treatment on improvement of tribological properties of diamond-like coatings (DLCs) on steels. It is shown that a maximum realization of the strengthening properties of DLCs is possible either through preliminary hardening of the substrate with ion implantation and additional thermal treatment or using etching of the coating surface with ions of active gas.

Friction, wear and service properties of i-C coatings on steel

Abstract We have developed a high-accuracy test unit that permits the testing of wear of coatings by a flux of solids. The unit features the following advantages: • - Special abrasive particle collectors are provided which enable one to determine accurately the number of particles that have caused the wear of a given specimen; • - Spatial homogeneity of the particle effect on a specimen is ensured, owing to scanning a particle jet perpendicular to the plane of its rotation. Friction studies and tests of i-C diamond-like coatings (DLCs) in a flux of solids have shown that the surface hardening effect is determined by the adhesion of coating to the substrate and by the critical degree of plastic deformation at the substrate coat interface. On the basis of the tests performed, a procedure of applying surface-hardening i-C DLCs on various tools has been developed which permits the operational life of tools to be extended considerably.

Modification of amorphous diamond-like films by bombardment with low-energy ions☆

Abstract The study is concerned with the influence that bombardment with low-energy (approximately 1 keV) ions of argon, oxygen, nitrogen or hydrogen exerts on properties of the amorphous diamond-like coatings (DLCs) produced by vacuum pulse sputtering of graphite in an arc discharge. It is shown that hydrogen treatment leads to the formation of C:H films whose composition depends on specific bombardment conditions. Bombardment with the other ions results in etching and smoothing of the DLC relief, while the film composition remains unchanged. Ionic bombardment increases the share of the diamond-like component in the film structure.

Practical use of strength and anticorrosion properties of amorphous carbon thin films

Abstract A study was made of the protective properties of amorphous C thin films deposited by the method of pulse sputtering of graphite on substrates having a temperature of approximately 175°C. It is shown that the films can be successfully used to improve the service properties of audio or video heads and surgical cutting instruments.

Service properties of cutting tools hardened with a diamond-like coating☆

Abstract Mill-type cutting tools with and without a hardening amorphous-carbon coating were tested for wear and serviceability. The feed rate, speed, and cutting width were varied. Mathematical processing was used to determine wear and service life as a function of the cutting parameters. It was found that the cutting edge may be blunted during coating application. The calculated dependences allow choice of the most favorable operating conditions for tools hardened with a carbon coating. The inferences made from the study were checked under actual conditions of operation. The results are reported.

Breakdown of a-C coatings on ion-implantation-modified metal alloys with a jet of abrasive particles

Abstract N+ and C+ were implanted (30 keV, 1017–1018cm−2) into amorphous diamond-like coatings (DLCs) produced by pulse-arc sputtering and into the substrates (stainless steel and hard tungsten-cobalt alloy) on which the DLCs were deposited. Wear resistance of the implanted DLCs and that of DLCs on the implanted substrates were studied. It is shown that ion beams stimulate graphitization of the DLCs and thus make the coatings weaker. By contrast, implantation of the ions into the substrates enhances wear resistance of DLCs, thanks to an increase in the material hardness under the coating and improvement of adhesion.

The use of deuterium for examination of C:H films

Abstract The method of nuclear reactions has been exploited to determine the hydrogen composition of diamond-like C:H films. Amorphous films 1–3 × 10 3 A thick were prepared from methane enriched with deuterium to 99% via decomposition from high-frequency or d.c. plasmas. Substrates were glass, Ge, or Cu. For determination of composition, use was made of 12 C(d, p) 13 C and D(d, p)T reactions on deuterons. A Van de Graaff electrostatic accelerator produced a beam of deuterons with energy 900 keV. Nuclear reaction products (protons) were observed with a surface-barrier detector of resolution 25 keV. Concentration ratios x = C D / C C were determined in the films; the ratios were found to be within the interval x = 1.5-0.5, depending on the sputtering conditions It was found that during measurement the amount of hydrogen in the films decreases as the absorbed dose W increases up to W ⋍ 5 × 10 4 MH , after which it stabilizes. Carbon content remains unchanged. The values of ∂ x /∂ W differed at the initial irradiation stages for films condensed under various conditions. The relation x = f ( W ) for films sputtered under the same conditions is similar for different substrates. This study has shown that ion irradiation results in the breaking of C-H bonds, the appearance of mobile hydrogen, and a simultaneous increase in the concentration of hydrogen “traps”.

Nanocomposite films prepared by arc-plasma deposition of titanium and carbon

The composition, structure, and properties of films prepared by depositing both titanium and carbon have been investigated. It was found that the films consist of an amorphous carbon matrix with uniformly distributed therein nanoparticles of titanium carbide (less than or equal to 20 nm in size). With increasing carbon concentration above 20 wt %, the film density decreases and the microhardness of the films increases, which reflects the diamond-like nature of the amorphous constituent of the composite film.