Ji Chengzhou

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.

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.

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.

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.

A study of pulsed high flux Ti, Mo, V and Y ion implantation for surface modification of resistances in wear, corrosion and oxidation

Abstract The resistances to wear, corrosion and oxidation of implanted H13 steel using pulsed Ti and Y ions were studied. The Ti and Y ions were produced from a metal vapor vacuum source (MEVVA). The instantaneous beam current was from 0.3 to 1 A and energy was from 25–50 keV. The target temperature was raised to 300°C for a flux of 38 μA cm−2 and to 600°C for a flux of 76 μA cm−2. The hardness of Ti-implanted steel increases with ion dose and decreases with ion flux. The wear resistance of Ti-implanted steel is 3–3.7 times that for the unimplanted steel. Precipitates of Fe2Ti were observed by X-ray diffraction and high energy electron microscopy (HVEM). The size and amount of Fe2Ti increases with increasing ion dose and ion flux. The oxidation barrier of Y-implanted H13 steel formed during oxidation at 800°C for 10 min was measured by RBS. The oxidation rate of Y-implanted steel was 8–10 times less than the unimplanted steel. The electrochemical properties of Ti and Y implanted steel in 1 mol H2SO4 or solution of NaCl were studied. The results show that the Y implantation is effective for improvement of corrosion inhibition of H13 steel, GCr15 and 304 stainless steel.

Yttrium ion implantation in pure aluminum

The penetration depth of yttrium ions extracted at 30 kV from a metal vapor vaccum arc source reaches about 150 nm in pure aluminum; the maximum retained concentration is 20-50 at.% for varying doses of 5×10 16 to 1×10 18 cm -2 . Upon post-annealing at 600 °C, the implantation-induced YAl 3 (rhombohedral Bravais lattice with 12 atoms per unit cell) transforms in part into YAl 3 (hexagonal Bravais lattice with eight atoms per unit cell); yttrium diffuses deep into the bulk aluminum (600 nm) with a diffusion coefficient of 3.56×10 -13 cm 2 s -1 ; the directive diffusion and incorporation of foreign iron atoms result in the production of YFe 3.5 Al x (x<17). No transition phase is observed at the precipitate-aluminum interfaces

Surface modification of non-semiconductors by ion beams in China

Abstract The MEWA ion source has stood out for the surface modification of materials by direct ion implantation. Concurrent implantation with multiple ion species is more efficient in tailoring the surface sensitive properties of solid materials. Ion beam assisted synthesis of surface coating layers has also found increasing applications. The achievements obtained in the past few years in China will be reviewed and successful examples are introduced.

Annealing behaviour of H13 steel implanted with N, Ti and Ti + N

Abstract Ion implantation is a non-equilibrium process. After annealing, the process proceeds from its non-equilibrium state and the radiation-induced damage will be removed gradually. The hardness of Ti-, N- and Ti + N-implanted layers of H13 steel as a function of the annealing temperature was obtained. The hardness increased with increasing annealing temperature ranging from 400 to 600 °C. The maximum hardness was obtained when annealing at a temperature of 500 °C for 20 min; this hardness is 62% greater than that of the unnealed specimens. The compounds Fe2Ti and Fe2N have been identified by X-ray diffraction and transmission electron microscopy. After annealing, the compounds still remain in the implanted layers. The H13 steel is strengthened by the compounds and the dislocations.

A cesium sputter negative ion source using a multilaminate wire mesh ionizer

Abstract A new ventilated surface ionizer has been developed for a 860A cesium sputter negative ion source operated at BNU. The new ionizer consists of a multi-laminate nickel wire mesh and a spiral heater, and is spherical in shape. Low pressure cesium vapour diffuses through the wire mesh to the extraction side of the ionizer, meanwhile the neutral cesium can be ionized. The ionizer is capable of producing a positive ion current up to milliampere range. The negative ion current is 50 μA for P− and more than 150 μA for 0− and Si−.