W.J. Zhao

Behaviour of MEVVA metal ion implantation for surface modification of materials

Abstract MEVVA ion implantation of Mo, Mo + C and Ti + C in H13 steel at high ion flux was studied. The results show that dispersive hardening phases grow with increasing ion flux. The growth of the phases is accelerated by annealing. The resistance to wear and corrosion for Mo-implanted steel is improved relative to unimplanted steel. After corrosion, the dispersive hardening phases which inhibit corrosion can be observed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). A dense network of phases for Mo + C-implanted steel is observed by SEM and TEM. The corrosion resistance of Mo + C-implanted H13 steel is much better than that of Mo-implanted H13 steel. The corrosion current density for Ti + C-implanted H13 steel is very small (0.1 mA cm −2 ); after annealing, the current density is near zero. SEM observation shows that, after corrosion for 50 voltage loops, no corrosion trace can be observed.

The thermodynamical process in metal surface due to the irradiation of intense pulsed ion beam

Abstract In this paper, a new simulation model of interactions between IPIB and target material was constructed, that is T-coupled fluid elastoplastic equations, considering thermal conduction of target materials. The calculation program steipib was written with C ++ language. Meantime the distributions of energy deposition of intense pulsed ion beam (IPIB) with the energy and time spectrum were studied carefully as pulsed heat sources. As the results of the thermodynamical simulation calculation for the distributions of temperature and its gradient, stresses near the surface layer, the generation and propagation of shocks and so on are given. Also important influences of pulse parameters of IPIB on the ion beam modification of materials are discussed. The radical factor, leading to surface modification by energy impinging of IPIB, is the high power density of IPIB or the high absorption power density of the target. Moreover, the energy-based modification mechanism with the main characteristics of the flash heating and the long-range interaction was explained. Especially, the strengthening effects at the backside of the thin target under the influence of some shock were predicted and proved experimentally.

Intense pulsed ion beam sources for industrial applications

The different kinds of intense pulsed ion beam (IPIB) sources and their applications to surface modification of materials, e.g., IPIB technology, are reviewed. Intense pulsed energy effects on the surface microstructure as well as properties of 45# steel have been experimentally investigated in this work with different pulse parameters of the IPIB, such as current density and pulse duration. It is shown that ion beams with power density (106–108u200aW/cm2) are very promising ones, but the modification result is affected significantly by the pulsed ion beam parameters. New requirements to the IPIB sources for the industrial applications are discussed.

The corrosion behavior of nano-meter embedded phase in Ti implanted H13 steel

On the SEM micrographs of Ti implanted H13 steel, a tree-branch-like structure can be observed. Further investigation with TEM shows that the newly formed composition is a formation of nano-meter FeTi2 phase in Ti implanted layer. The layer with a relatively high corrosion resistance has been formed in Ti implanted H13 steel with this structure. The results of electrochemical measurement show that the corrosion current density decreases obviously with an increase of ion dose. The corrosion current density in Ti implanted steel with a dose of 1.3×1018/cm2 is 8–20 times less than that of Ti implanted steel with a dose of 6×1017/cm2. The corrosion behavior of Ti implanted steel with a dose of 6×1017/cm2 could be further improved as the sample was annealed at 500°C for 20 min and the corrosion current density decreases by 48–80 times compared to that of non-implanted samples. The corrosion trace was not observed on the annealing sample by SEM, after multi-sweep cyclic voltammetry of 40 cycles were performed. This indicates that terrific corrosion resistance can be obtained after annealing for Ti implanted sample.

Numerical analysis of thermodynamical process in the thin metal samples irradiated by IPIB

Abstract In this paper, we simulate, based on our one-dimensional coupled fluid–plastic model, the thermodynamical processes in the thin metal samples that are irradiated by intense pulsed ion beam (IPIB) with different pulse parameters. The pulse parameters are: ion energy from 300 to 1000 keV, current density from 10 to 100 A/cm 2 and pulse duration from 10 to 80 ns. With the calculation result, distributions of the sample densities and temperatures are discussed. Furthermore the shocks generated by IPIB are paid more attention in our discussion, including their generation, propagation, reflection at the back and surface of the sample, and its possible influence on the sample properties as well.

Study of tribological properties of high-speed steel implanted by high-dose carbon ions

Abstract The changes in tribological behaviour of high-speed steel (M2) samples implanted with carbon ions at high fluences (5×10 17 ∼3×10 18 xa0cm −2 ) have been studied. The ion energies used were 50 and 100xa0keV leading to a modified layer of 200 and 400xa0nm, respectively. Obviously, the samples show an improved tribological behaviour, although the microhardness of the surface decreased after implantation. Tribological measurements, microhardness measurements, RBS, SEM and EDX analyses were performed before and after ion implantation. The experimental results are discussed, and it is concluded that the improvement of wear behaviour can be correlated to an improved toughness of the near surface layer modified by the ion implantation.

Properties of IBAD alumina coatings of different thicknesses

Abstract Alumina coatings of different thicknesses were deposited on CK45 steel substrate under the bombardment of 10xa0keV Ar + with an incidence angle of 45° by using an ion beam assisted deposition (IBAD) facility. The composition and structure of these coatings was analyzed by RBS, AES and XRD methods. The adhesion between the coatings and the substrates was measured by pull-off tests, and the microhardness was also measured using a Vickers indentor. Corrosion protection ability to the steel substrate, both in Cl − -containing and non-Cl − -containing buffered acetic solutions was evaluated by electrochemistry method. Experimental results show that a stoichiometric, amorphous Al 2 O 3 coating with excellent adhesion to CK45 steel substrate can be obtained by using the IBAD technique. Microhardness and corrosion resistance can be improved significantly by the use of alumina coating, and the amount of improvement depends greatly on the coating thickness.

Simulations of intense pulsed ion beam uniformity in a planar magnetically insulated ion diode

Using the self-consistent, 2-1/2-dimensional particle-in-cell MAGIC code, based upon the explosive emission model, we have simulated the characteristics of the proton flux extracted from a planar magnetically insulated diode with a 200-mm-wide and an 8 mm anode-cathode gap. Results of numerical calculation, e.g., the spatial distributions of the extracted proton current density vs time and the spatial distribution of particles in diode gap are presented at a diode voltage of 300 kV with 40 ns pulse duration and an externally insulating magnetic field of 0–4Bcrit. With the increase of the magnetic field, the uniformity of the extracted proton flux is significantly improved; however, the maximum of the proton current density and one of the proton energy density decrease from 150 to 45 A/cm2 and from 1.0 to 0.3 J/cm2, respectively, when B varied from 0 to 4Bcrit. The effects of the magnetic field on uniformity of the extracted proton flux are discussed in this article.

The phase and microstructure changes in 45# steel irradiated by intense pulsed ion beams

Intense pulsed ion beam (IPIB) treatment is a new technology of surface modification. Compared to traditional ion implantation, the intense pulsed energy effect takes the main role in the IPIB modification processes. Therefore, the phase and microstructure changes induced by IPIB irradiation is much stronger than those induced by traditional ion implantation. We investigated the phase and microstructure changes in surface layer of 45# steel samples irradiated with intense pulsed ion beams at different pulsed energy densities by transmission electron microscopy (TEM), scanning electron microscopy (SEM) and X-ray diffraction (XRD). The nanohardness distribution in a cross-section of the sample surface layer was also measured. The ferrite and laminated pearlite structures in near surface layer was changed in different degrees that grow with the pulsed energy density. The depths of these modified layers are much deeper than the ion range. Polished surfaces of samples were roughened with 10 μm-scale width and 1 μm-scale depth craters. The results of above analyses are discussed.

The surface microstructure of high-dose, carbon-implanted high-speed steel

Abstract Carbon ions generated by MEVVA ion facility with 70-keV energy were implanted into high-speed steel(HSS) samples at doses of 5×10 17 ∼3×10 18 xa0cm −2 . RBS, TEM, XRD, SEM and EDX were used to analyze the surface microstructure of implanted samples. It has been found that the dose reached saturation as the fluence reached 1×10 18 xa0cm −2 . The W, V concentration on the surface became much higher after implantation. An amorphous layer embedding some nano-size carbide particles was formed on the surface of high-dose carbon-implanted samples. There are also some unclear nano-structures appearing in the tungsten-rich area under the TEM.