Zhang Tonghe

Influence of the structure of implanted steel with Y, Y + C and Y + Cr on the behaviors of wear, oxidation and corrosion resistance

Abstract New methods were studied to improve the properties of corrosion, wear and oxidation resistance of implanted H13 steel using ions of Y, Cr, Y + C and Y + Cr, produced by a pulsed metal ion source (MEVVA). The results show that the behaviors of wear, corrosion and oxidation resistance were improved obviously for four kinds of ion implantation into H13 steel. The oxidation resistance of single Y implantation at 25 μA cm −2 is better than at higher fluxes. The wear and oxidation resistance of Y + C are better than those of Cr, Y and Y + Cr implantation. The corrosion resistance of high dose implantation is better than that of low dose implantation. The structural changes of the implanted layer before and after oxidation were measured by X-ray diffraction. An improvement in the above-mentioned properties is closely related to the structural change of yttrium-iron alloy and yttrium-iron oxidation compounds. The compounds were formed during a short-time (10 min) oxidation. Because of the compound formation, a strong Y atom concentration profile appeared. The shape of the profile is constant during oxidation at 800 °C for 40 min. Finally, the mechanism of influence of the oxidation compounds and the strange shape of the profile on the properties of the implanted layer is discussed.

Formation of intermetallic compounds with a high flux pulse molybdenum ion beam in steel and aluminium

Abstract Intermetallic compounds of molybdenum and tungsten implanted into H13 steel and aluminium were measured by transmission electron microscopy (TEM) and X-ray diffraction. Ions extracted from a metal vapour vacuum arc source with around 25–100 keV energy and a dose range (1–5) × 10 17 cm -2 were used for implantation. The ion fluxes were 25, 47, 68 and 320 μA cm -2 . It was found from the results that the target temperature increases with increasing ion flux from 310 °C (25 μA cm -2 ) to 580 °C (68 μA cm -2 ). Intermetallic compounds such as FeMo, Al 2 Mo, Al 12 Mo, Fe 7 W, Fe 2 W and Al 5 W, were easily observed by TEM and X-ray diffraction when the flux was greater than 47 μA cm -2 . In situ observation in a high voltage transmission electron microscope (HVEM) was used to investigate the structure and formation of intermetallic compounds of molybdenum-implanted H13 steel. The electron diffraction pattern of FeMo precipitates appeared at 500 °C. Recrystallization and grain growth occurred at 650 °C.

Industrialization of MEVVA source ion implantation

Abstract Ion implantation is being successfully applied for the reduction of corrosion, wear and oxidation of materials. As a result, ion implantation as an engineering tool is a powerful and relatively important technique. In order to develop applications of ion implantation for precision tooling, moulds and large number of engineering components, improvement in the MEtal Vapor Vacuum Arc (MEVVA) source implantor for industrial ion implantation now offers more attractive costs per unit area and a potentially greater throughput. Material modification was produced by MEVVA source implantation at high target temperature (200∼550°C) with high ion flux (25∼100 μA/cm 2 ). Metal ion implantation has yielded good results in the improvement of drills, cutters, dies, bearings and off-gas pumps for returnable artificial satellites using MEVVA source implantors. The results show that reduction of manufacturing costs and the challenges to improve component performance justify consideration of metal ion implantation in industrial processing. The ion implantation workshop was established with two implantors for industrial application. Millions of drills were processed per year. A large number of ion-implanted products have been exported up to now.

Influence of nanostructure on electrical and mechanical properties for Cu implanted PET

Abstract Polyethylene terephthalate (PET) has been modified by 40 KeV Cu ion using a metal vapor vacuum arc (MEVVA) source to fluence ranging from 1×10 16 to 2×10 17 ions/cm 2 . The surface morphology was observed by atomic force microscopy (AFM). The Cu atom precipitation and nano-structure of Cu implanted PET were observed. It is believed that the structure change improves the electrical properties and wear resistance of PET. The electrical properties of PET have been improved extremely after ion implantation. The surface resistance of implanted PET decreased obviously with an increase of ion dose. When metal ion dose was higher than 1×10 17 cm −2 , the surface resistivity of PET could be less than 0.1 Ω m. The results show that the conductive behavior of a Cu ion implanted sample is much better than that of non-metal Si- and C-ion implanted one. After Cu implantation, the surface hardness and Youngs modulus increase and the cross-section area of cutting groove is narrow and shallow comparing with the unimplanted PET. The modification mechanism of PET was discussed.

Polymer modification by MEVVA source deposited and ion implantation

Polyethylene terephthalate (PET) has been modified by Ti, Ni and W deposition using a metal vapor vacuum arc (MEVVA) source and implantation. The surface resistance of deposited PET could decrease to several hundred ohms. The adhesion of metal coating on polymers is very strong. The thickness of the deposited metal coating could be controlled from tens of nanometers to 1 μm. The hardness for thick Ti and W deposited PET is 3.81 and 2.54 GPa, which are several times greater than that of PET. The elastic modulus of deposited PET increases also. Similar results have been observed for other metal implanted PET. The thickness and atomic distribution of deposited metal coating was analyzed using RBS. The surface structure has varied after deposition and implantation. It is believed that the change would cause the improvement of the conductive properties and wear resistance.

The influence of Ti, N and Ti + N implantation on phase change, microstructure, growth of metallic compounds and correlated effects in hardness and wear resistance in H13 steel

Abstract The lattice damage, small intermetallic compound (Fe 2 Ti), metallic compound (TiN, Fe 2 N) formation and supersaturated solutions of Ti or Ti + N-ion implanted into steel with various ion doses and energies were measured by TEM and X-ray diffraction Formation and growth of the metallic compound Has found to depend on ion dose and energy. Change of phases and microstructure were particularly enhanced with high dose and high energy. Metal hardening also increases with increasing ion dose, energy and the amount and size of metallic compounds. Specimens implanted at target temperature ranging from 300°C to 400°C (HT) or implanted at room temperature (RT) and then annealed at temperature ranging from 300 to 500°C, showed significant increase in hardness. The wear resistance of high energy and high dose implanted steel is better than that of low energy and lower dose implantation. The wear rate decreases 2–2.6 times for low temperature implantation, 10.4 times for HT implantation and high energy implantation. The Fe 2 Ti and TiC precipitates, phase and microstructural changes in the implanted layer are responsible for such a drastic reduction in wear.

The formation of metallic silicides of Ti, Y, Fe, Mo and W using metal vapour vacuum arc implantation

Abstract The formation of metallic silicides was studied using implantation into Si with ions of Ti, Y, Fe, Mo and W produced by a metal vapour vacuum arc ion source. The electrical properties were measured by four-probe and spread-resistance probe devices. The resistivities are from tens to hundreds of micro-ohm centimetres for the implantation of these ions. The resistivity of Ti-, Y- and Fe-implanted layers decreased obviously with increasing ion flux. In contrast, the lowest resistivity is found for Mo and W implantations at 50 μA cm-2. The glossy surface changes into a rough surface and the resistivity increases, if the ion flux of Mo and W is larger than 75 μA cm-2. The silicide phases were distinguished by X-ray diffraction and Rutherford backscattering spectrometry. The metallic silicides TiSi, TiSi2, YSi, YSi2, FeSi, FeSi2, MoSi2 and WSi2 were fully formed if the ion flux was as high as 50 μA cm-2. The surface atomic ratio was about 40%–60% for Ti, Y and Fe, and 20%–25% for Mo and W, if implanted doses of (3–5) × 1017 cm-2 were used. The distribution depth of the silicides was about 30–80 nm. The new process technique is suitable and can be employed for shallow junction technologies of very-large-scale integration.

Metallic ion implantation by using a MEVVA ion source

Abstract Metallic ions (Ti, Mo, W, V, Ni, Y, Fe and Al) extracted from a MEVVA source have been implanted up to high doses (>1 × 1017 cm−2) into Al and H13 steel. Because of beam heating, rather low energy ions could penetrate quite deeper in the substrates than predicted, stable intermetallic compounds appear as fine precipitates in the doped region, and hence the retained concentration of implants even exceeds the sputter-limited maximum. Multiply charged beam, enhanced diffusion and chemical reaction give great influences to the concentration distribution of implants. All these features are strongly dependent on the chosen ion-target combination.

Improvement of Friction and Wear Resistance for Ta or Ta+C Implanted H21 Steel

Ta and C ions extracted from a metal vapor vacuum arc ion source were implanted into H21 steel, with an implantation dose of 3 × 1017 cm-2, extraction acceleration 42 kV, and average ion beam flux about 40 μAcm-2. Rutherford backscattering spectrum was used to measure the surface composition after Ta or Ta+C implantation. Observation of phase induced by Ta and C implantation was carried out by x-ray diffraction analysis. Experimental results showed that the wear rate of the implanted layer dropped 30% for Ta ion implantation and by a factor of 2.5 for Ta+C dual ion implantation. Thus Ta+C dual ion implantation was found to significantly reduce the friction coefficient of H21 steel. The wear mechanisms of the implanted layer were discussed.

A study of enhanced diffusion during high dose high flux pulsed metal ion implantation into steel and aluminium

Abstract The depth profiles of metal ions implanted into steel and aluminium were measured by Rutherford backscattering (RBS). The ions of Mo, W and Y, produced by a metal vapour vacuum arc ion source (MEVVA) were implanted at an energy range from 25 to 50 keV for doses of (2–5)×1017 cm−2 into H13 steel and aluminium. Beam currents were from 0.5 to 1.0 A. The beam flux is in the range of 25 to 75 μAcm−2. In order to simulate the profiles, a formula which includes the sputtering yield, diffusion coefficients and reaction rate was obtained. The results demonstrate that the penetration depth and retained dose increase with increasing beam flux for Mo implanted into aluminum. The peak concentration of Mo implanted H13 steel increases with increasing ion flux. In contrast to this for Y implantation into steel, the peak concentration of Y decreases with increasing ion flux. For an ion flux of 25 μA cm−2 for Mo, Y and W implantation into steel, the penetration depth and retained dose are 3–5 times greater than the theoretical values. The diffusion coefficients are about 10−16 to 10−15 s−1. If the ion flux is greater than 47 μA cm−2, the penetration depth and retained dose are 5 to 10 times greater than the theoretical values for Mo implanted aluminium. The diffusion coefficients increase with increasing ion flux for Mo implanted aluminium. The diffusion coefficients hardly change with increasing ion flux for Y and Mo implanted H13 steel. The retained dose increases 0.43 to 1.16 times for Y implanted steel for an ion flux of 25 μA cm−2. Finally, the influence of phases precipitates, reaction rate and diffusion on retained dose, diffusion coefficient and penetration depth are discussed.