Search

The paper presents the adhesive strength measurements of the Ni–Cu surface alloy formed on a copper substrate at a different thickness of the transition layer. The formation of the surface alloy is provided by the low-energy high-current electron beam of a microsecond duration; the different thickness of the transition layer is varied by the thickness of the nickel film sputtered. The multiple deposition-irradiation process is performed during one vacuum cycle. It is found that the cross-section of the film (Ni)-substrate (Cu) interface is rather developed and curved. The transition layer thickness reduces with increasing thickness of the deposited nickel film. Scratch testing shows that the adhesive strength of the Ni–Cu surface alloy obtained by using the low-energy high-current electron beam, is higher than that of the sputter-deposited surface alloy. The highest adhesion is observed for the Ni–Cu surface alloy obtained by the nickel film deposition 0.125 μm thick. In this case, the crack formation and localized film delamination occur under the critical loads of 15 and 17 N, respectively. Nevertheless, a complete delamination of the surface alloy is not observed.

The structural features of the surface of a TiNi-based powder alloy produced by diffusion sintering are studied. Two-dimensional porous samples based on a TiNi powder alloy are manufactured for the experimental investigation of their structural features by the methods of non-destructive testing. It is determined that the phase composition of the TiNi-based powder alloy is represented by the TiNi (B2) austenitic phase and precipitates of the secondary phases enriched with nickel – Ti3Ni4 and titanium – Ti2Ni. The chemical compositions of the TiNi compound and the Ti2Ni secondary-phase particles are determined. A three-dimensional reconstruction of the surface of the TiNi-based powder alloy is performed by optical profilometry. It is shown that, depending on the sintering temperature regime and particle size distribution of the TiNi powder, it is possible to obtain a developed rough surface with a roughness coefficient within Ra = 64–87 μm. An analysis of the surface microstructure of the resulting material indicates the existence of several types of terraced relief — hexagonal islands of regular shape 5–10 μm and large terraced structures up to 30– 40 μm in size.

Results of investigations of acoustic signals induced in a copper plate irradiated with a microsecond lowenergy high-current electron beam (LEHCEB) are presented. The characteristic acoustic signal waveforms, their amplitudes, phases, and frequencies are experimentally measured. It has been established that the acoustic signals induced by LEHCEB irradiation have groups of characteristic spectral components with fundamental frequencies of 6, 11, 22–24, 80, and 100–120 kHz whose amplitudes increased with charging voltage. It has been established that from the change of the 80 kHz harmonic with the charging voltage, the beginning of LEHCEB generation, its stable or unstable phase, and the beginning of target melting can be traced. It has been found that for a fixed charging voltage of each pulse in a series, the amplitude and phase-frequency structure of acoustic signals are almost the same.

The paper presents research results of the synthesis of Ni–Al surface alloy performed in a single vacuum cycle via magnetron sputtering of Ni (0.5 μm)–Al (1.5 μm)–Ni (0.5 μm) composite coating onto a steel substrate and its successive single pulse irradiation with low-energy, high-current electron beam (LEHCEB) of a microsecond duration. The numerical solution of the heat equation is used to determine the optimum LEHCEB modes which provide melting of all the films deposited. It is shown that the single pulse irradiation of thin films leads to the formation of the surface alloy consisting mainly of high-melting-point NiAl intermetallic phase. The structure of the surface alloy is a 2 μm thick homogeneous coating with 2×4 μm globules beneath separated by a thin layer of the substrate material. It is found that the wear resistance of the obtained Ni–Al surface layer is 2.7 times higher than that of the untreated steel substrate.

The paper presents research results into the microstructure of Cu–Cr composite material affected by the highcurrent vacuum arc. The investigation of the electrode cross-sections allows us to emphasize two zones both for anode and cathode: 1) the exposure zone of the vacuum arc and 2) the virgin material. The first zone locates on the surface of electrodes and is just a zone that crystallizes after the electrode melting due to the exposure to the high-current vacuum arc. It is interesting that on anode there appears a narrow, transition layer enriched with chromium nearby the virgin material and with copper in the exposure zone of the vacuum arc. The formation of such a layer on cathode is not observed.

The paper deals with the formation of the stainless steel-copper surface alloy which occurs during the single vacuum cycle. Deposition of the stainless steel film onto a copper substrate is performed via successive magnetron sputtering followed by its liquid-phase mixing with copper using the low-energy, high-current electron beam of microsecond length. Numerical calculations are used to identify the optimum irradiation modes for the surface alloying. It is found that the optimum irradiation modes provide the homogeneous surface alloying, and the copper concentration in the obtained layer increases with the increase in energy density of the low-energy, high-current electron beam. The formation of the stainless steel-copper surface alloy increases the wear resistance of copper specimens by 7.5 times as compared to the original specimens. In addition, it is ascertained that the wear resistance of the surface alloy exceeds that of the common film coating (1 μm) more than 5 times.