A. Anttila

Tribological characteristics of diamond-like films deposited with an arc-discharge method

Using an are-discharge method, we deposited a diamond-like carbon film 600 nm thick on hardened steel. Characterization of the film was carried out with Raman spectroscopy. In dry sliding wear and friction tests, with a hardened steel pin as a counterpart, we obtained a friction coefficient between 10000 and 20000 cycles, with the maximum value of 0.18. The value decreased to 0.12 after about 100000 cycles. We obtained a wear coefficient of 7 × 10−17 m3/mN. A transfer layer formed on the pin during sliding and probably had the dominating effect on the tribological behavior. We observed in nanoindentation measurements that the film softened in a wear track during the first 20000 cycles. Although fracture pits on the wear track occurred, fracture is not the dominant failure mechanism of these films. Degradation of good tribological properties was caused mainly by partial wear-through of the film after 370000 cycles and by a subsequent redeposition of the transfer film on the wear track during prolonged sliding.

Comparison of diamondlike coatings deposited with C+ and various hydrocarbon ion beams

The mechanical properties of the diamondlike coatings deposited with mass‐separated C+, CH+3, CH+4, and C2H+2 ion beams have been compared. The hardness, abrasive wear resistance, and adhesion of the coatings prepared with the C+ ion beam were superior to those of the coatings prepared with other ions. The most serious drawback of the films prepared with hydrocarbon beams was their brittleness and weak adhesion.The mechanical properties of the diamondlike coatings deposited with mass‐separated C+, CH+3, CH+4, and C2H+2 ion beams have been compared. The hardness, abrasive wear resistance, and adhesion of the coatings prepared with the C+ ion beam were superior to those of the coatings prepared with other ions. The most serious drawback of the films prepared with hydrocarbon beams was their brittleness and weak adhesion.

High adhesion of diamond-like films achieved by the pulsed arc-discharge method

Abstract The existence of an extremely good adhesion between a silicon substrate and hard diamond-like films (sp 3 bonding 78%) prepared by the pulsed filtered arc-discharge method has been pointed out. The deposition of the films was performed at room temperature with the rate 1 μm/h. The high adhesion was achieved by pretreating the silicon surface with “high energy” (140 eV) carbon plasma ions. The compressive stress of the films arisen during the preparation process caused the silicon surface layer to peel off even to the depth of 25 μm in bulk silicon. This effect indicates difficulties in the use of thick (> 1.5 μm) diamond-like films in the applications.

Correlation of carbon ion energy with sp2sp3 ratio in amorphous diamond films produced with a mass-separated ion beam

Abstract The ratio of sp 2 and sp 3 bondings in amorphous diamond films grown by a mass-separated carbon ion beam has been measured with the ESCA method. The energy of the carbon ion beam ranged from 5 to 1000 eV. The maximum of the sp 3 bondings (78%) was in the ion energy region of 40–140 eV. The results correlate well earlier molecular dynamics simulations.

On the optimization of an external PIXE arrangement

Abstract An external PIXE arrangement where the PIXE measurements can be normalized directly by the collected beam charge is presented. In the arrangement presented the beam current measurement was shown to be independent of the sample material by comparing the K-peak intensities of the Ar component of the air with the collected beam charges. In addition, a simple vacuum safety valve for the breakdown of the exit foil is presented and the importance of effective sample cooling and proper choice of exit foil material is emphasized.

Annealing behavior of implanted nitrogen in AISI 316 stainless steel

The behavior of implanted nitrogen during post‐implantation annealing has been studied at 400, 450, and 500u2009°C by depth profiling of 15N‐implanted samples using the nuclear resonance broadening method. During the initial states of the annealing the nitrogen depth profiles behaved as if all the nitrogen would be able to diffuse, i.e., to be in solution, whereas for the longer annealing times the concentration of migrated nitrogen in the unimplanted region reached equilibrium with the implanted layer. The diffusion coefficients were determined as well as the equilibrium concentrations at the temperatures involved. The published values of the diffusion coefficients were extended to temperatures more than 500°u2009C lower than before.

Energies of carbon plasma beams in the deposition of diamond-like coatings with the pulsed-arc-discharge method

The carbon plasma ion energies produced by the pulsed filtered arc-discharge method have been measured as a function of the anode-cathode voltage. The energies were determined by using the electro-optical time-of-flight method. The highest anode-cathode voltage was 5 kV and yielded the energy of 140 eV for the plasma ions. In addition, it was demonstrated that a rather slight change of the parameters in the arc-discharge method has a strong effect on the plasma ion energies and the properties of the diamond-like coatings prepared.

Tribological characterisation of hard carbon films produced by the pulsed vacuum arc discharge method

Abstract Hard diamond-like carbon (DLC) films were deposited on silicon and high-speed steel substrates using a pulsed vacuum arc discharge method. The plasma plume was focused on the substrate using a direct electromagnetic coil. Several methods were used for coating characterisation. The film composition was analysed using Rutherford backscattering spectroscopy and forward recoil spectroscopy. About 0.5 at.% oxygen and about 1 at.% hydrogen was detected in the film. The tribological properties of the carbon films were studied using pin-on-disc tests. The counterface materials employed were alumina and hardened steel (AISI 52100 and M50) pins, which were slid against the coated substrates. The friction coefficient was measured and the wear surfaces were studied. The sliding speed was in the range 0.02–0.6 m/s and the load in the range 5–20 N. The tests were carried out in air with a relative humidity of 50±2% and at a temperature of 24±3 °C. The test results show that the DLC coatings produced for this study generally had a coefficient of friction (μ) of about 0.2. The lowest value measured was μ =0.14. The wear resistance of the coatings was good, provided that the adhesion to the substrate was sufficient. The comparative tests with titanium nitride and titanium aluminium nitride coatings showed that DLC films are considerably more wear resistant than titanium-based coatings.

Analysis of boron using the (p, α) reaction

Abstract The applicability of the strong and broad resonance of the reaction 11 B(p , α) 8 Be at Ep = 675 keV to the elemental analysis of boron has been studied. To eliminate matrix effects and to optimize the measuring conditions a systematic study of the absolute thick-target yields of α-particles following proton bombardment has been carried out at Ep = 0.7 and 1.0 MeV for the elements Z = 3−9, 11−17s by. Summary spectra showing the α-peaks of light elements of interest in the elemental analysis of boron are given. An external beam measurement system has been developed to allow measurements to be carried out in He-gas at atmospheric pressure. Thus, problems arising in vacuo with insulating, medical and biological samples can be avoided. The detection limits of boron range from 0.1 ppm for biological samples containing nitrogen to below 0.01 ppm for samples with a low nitrogen concentration. An additional advantage of the method is that Li, F and N can be determined simultaneously with the boron analysis.

Wear and hardness of diamondlike coatings prepared by ion beam deposition

The wear rate of 10‐μm‐thick 12C coatings prepared by mass separated ion beam deposition has been measured to be 60 times lower than WC+Co hard metal and 10 times lower than the conventional hard coating material TiN. The hardness of the 12C coatings was measured to be at least the same as that of the natural diamonds.