Silicon-doped hydroxyapatite-based (Si-HA) coatings were deposited via radio frequency (RF) magnetron sputtering on the surface of titanium that was treated with a pulsed electron beam. This study ...aimed to evaluate the effect of Si doping on the structure and mechanical properties of thin HA films. The content of the silicon was 1.2 and 4.6at.% for the coatings prepared using the Si-HA precursor powders with a chemical formula Ca10(PO4)6−x(SiO4)x(OH)2−x where, x=0.5 and 1.72. Pure HA (Ca10(PO4)6(OH)2) coatings were deposited for comparison. The as-deposited films were analysed with respect to their composition, state of chemical binding and microstructure using XPS, FTIR, XRD, and SEM. We hypothesized that the addition of Si would affect the mechanical features of the coatings due to microstructure changes. The effect of the introduction of Si on the nanohardness and the Young's modulus as well as the adhesion strength and scratch resistance of the HA coating was investigated using nanohardness testing and a scratch test, respectively. Examination of the coating microstructure using SEM and AFM revealed that Si doping influenced the surface morphology and led to a smaller grain size. The tendency to form an amorphous structure also increased with an increase in the Si content. A monotonous decrease in both the nanohardness and the elastic modulus was observed with an increase in the Si content. A maximum nanohardness of ~7GPa was obtained for the Si-free HA coating, whereas the hardness decreased to ~4.3GPa for the films with a Si content of 1.2at.%. The addition of 4.6at.% Si to the HA coating resulted in a reduction in the elastic modulus, whereas the nanohardness was very similar to that of the uncoated substrate. The adhesion behaviour of the coatings demonstrated different responses. In the case of pure HA coatings, failure occurred due to the low cohesion of the coating, whereas the crystalline Si-HA coatings with a Si content of 1.2at.% deformed plastically without crack formation and without detaching from the titanium substrate, which resulted in a greater coating stability.
•Silicon incorporation has an influence on surface morphology of the films.•Hydroxyapatite-coated titanium presented superior mechanical properties.•A maximum nanohardness of ~7GPa is obtained for the Si-free HA coating.•Crystalline Si-HA coatings deform plastically without detaching from the substrate.
The titanium-based alloys with 2–3 at.% of chromium (TiCr) and molybdenum (TiMo) were produced on the top of titanium samples by means of the high-intense pulsed electron beam impact on the titanium ...with preliminary deposited Cr and Mo coatings. The TiCr and TiMo alloys were subjected to oxidation in open air atmosphere at temperature 600 °C. X-ray diffraction analysis (XRD), scanning electron microscopy (SEM) and energy-disperse X-ray microanalysis (EDX) were used for structure and elemental composition determination in the samples. The analysis of oxygen depth profiles showed the increase in oxygen penetration depth in the case of TiCr alloy in comparable to pure titanium. The oxygen concentration corresponding to stoichiometry of the oxide phase TiO2 was found on the depth equaled to the thickness of the TiCr alloy that shows the enhancement of the diffusion of oxygen in the modified layer. The diffusion of oxygen at the temperature of 600 °C is enhanced by decomposition of the solid solutions based on bcc β-Ti phase with free chromium and molybdenum atoms releasing. The free molybdenum atoms take part in the stabilization of TiO2 anatase phase while the free chromium atoms form intermetallic compound TiCr2 preventing the sample from oxidation.
•Oxidation resistance of TiCr and TiMo alloys under the open-air heating was investigated.•The free Cr atoms released from solid solution β-Ti(Cr) during heating form intermetallic phase TiCr2 preventing the surface from oxygen penetration.•The volume fraction of both modifications of TiO2 phase, rutile and anatase, is higher in TiMo alloy.
The formation of martensitic α′ and α′′ phases in Ti-6Al-4V titanium alloy subjected to low energy high current pulsed electron beam (LEHCPEB) treatment with an energy density of 12–25 J/cm2 was ...revealed by X-ray diffraction and transmission electron microscopy. It was substantiated that the strain-induced phase transformation is the dominant mechanism underlying the deformation behavior of the melted surface layer of the titanium alloy samples during nanoindentation and scratch testing. It was found that the reverse transformation of the α′′ phase into the more close-packed α phase is responsible for the softening of the uppermost surface layer of the samples subjected to LEHCPEB treatment. The development of the direct and reverse α′′→α→α′′ martensitic transformations in the uppermost surface layer resulted in the improvement in elastic recovery of the treated Ti-6Al-4V samples after scratching.
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•LEHCPEB treatment leads to formation of α′ and α″ phases in melted surface layer of Ti-6Al-4V alloy.•Strain-induced phase transformations occur during nanoindentation and scratching.•α→α″ martensitic transformation results in increasing elastic recovery of scratch groove.
This study investigated the effect of the substrate morphology introduced by various substrate preparation techniques, namely acid etching (AE) and pulsed electron beam (PEB) treatments, on the CaP ...film morphology and mechanical properties. The morphology, nanohardness, and Young's modulus of the CaP coating deposited via radio-frequency (RF) magnetron sputtering were investigated by X-ray photoelectron spectroscopy (XPS), atomic force microscope (AFM), scanning electron microscopy and nanoindentation studies. The Ca/P ratios of the CaP coating deposited via RF magnetron sputtering onto titanium substrates treated using AE and PEB according to XPS were 1.73±0.03 and 1.72±0.04, respectively, which is close to the Ca/P ratio of 1.67 typical for stoichiometric hydroxyapatite (HA). The AFM experiments and nanoindentation studies revealed significant differences in the morphology and mechanical responses of the CaP films deposited onto acid-etched titanium substrates treated with PEB. Deposition of the CaP coating onto the acid-etched surface resulted in a rough surface with the presence of an island-like morphology. The CaP coating onto a smooth titanium substrate treated by PEB exhibited grains with irregular shapes and decreased size. The nanoindentation hardness and the Young's modulus of the HA coating deposited onto titanium treated by the PEB treatment were determined to be 7.0±0.3 and 124±3GPa, respectively, which are significantly higher than those of the CaP coating on the acid-etched titanium substrates. Moreover, the elastic strain to failure (H/E), the plastic deformation resistance (H3/E2), and the percent elastic recovery %R of the HA coating on titanium after surface irradiation with an electron energy density of 15J·cm−2 were determined to increase by ~23%, ~70% and ~53%, respectively, compared to the CaP coating on acid-etched titanium.
•Island-like morphology of calcium phosphate coating on titanium was observed.•Electron beam treatment of titanium resulted in surface smoothing of the coating.•Effect of electron beam treatment of titanium on the film nanohardness was revealed.•Enhanced resistance to plastic deformation for the coated titanium was observed.
In this paper the results of experimental study of microstructure changes in Zr–1Nb alloy after low energy high current pulsed electron beam surface modification and hydrogenation are discussed. ...Surface treatment was carried out with energy density equal from 5 to 25J/cm2 and impulses number equal from 1 to 5. Subsequent hydrogenation was carried out at temperature equal to 350°C until reaching the hydrogen concentration of 0.05wt.%. The structure was analyzed by X-ray diffraction, transmission electron microscopy and by means of electron–positron techniques.
•Zr was modified by pulsed electron beam with different modes and then hydrogenated.•Pulsed electron beam irradiation changes surface and defect structure at 100μm depth.•Dislocation loops and vacancy clusters are formed after electron beam irradiation.•Vacancy-type defects concentration increases after hydrogenation.
Combined technologies based on the use of concentrated energy fluxes, including low-temperature plasma and a pulsed electron beam, is currently considered to be an effective approach for surface ...modification of metals and alloys, cermet and ceramic materials. The purpose of the paper is to identify and analyze the patterns of changes in the elemental and phase composition, the state of the defective substructure, and mechanical properties of industrial steel Gr1J03502 subjected to combined treatment that includes plasma deposition of a powder coating based on the Ni-Cr-B-Si system and irradiation with an intense pulsed electron beam. The results obtained by optimizing the mode of the substrate surface fusion and the mode of powder deposition onto the molten surface of the substrate using low-temperature plasma generators of the original design are presented. It has been found that the optimum melting mode of the substrate surface is implemented with the following parameters of the plant: the feed rate is Vп = 50 … 150 mm/min, the distance is h1 = 30…100 mm, the scanning frequency is ω = 50 min−1, β = 75 … 90°, the amplitude is 90 … 100 mm, the plasmatron voltage is 160 V, the current strength is Im = 100 … 120 А. The optimal spraying conditions of the powders are as follows: h1 = 30÷50 mm; h2 = 100÷120 mm; β = 75÷90°; α = 45÷50°; ω = 50 min−1; Um = 140÷160 В; IS = 350÷400A; Im = 80÷100 A; GH (sprayed powder consumption) 0.8÷1 g/s. The characteristics of a plasma jet generated by an electric arc plasmatron are presented. The parameters of the electron beam are as follows: the energy of accelerated electrons is 18 keV, the energy density of the electron beam is 20 J/cm2 and 40 J/cm2, the pulse duration of the electron beam is 200 μs, the pulse repetition rate is 0.3 s−1, and the number of pulses is 10. It has been shown that plasma spraying of a powder coating leads to formation of a high relief surface containing micro and macropores, microcracks, and particles of the sprayed powder. Subsequent treatment of the modified surface with an intense pulsed electron beam of a submillisecond duration in the melting mode of the surface layer is accompanied by smoothing of the coating surface, saturation of the crystalline lattice of the steel surface with Ni, Cr, B, and Si atoms, formation of submicron-sized dendritic crystallization cells, precipitation of nanosized particles of the second phase, and formation of a quenching (martensitic) steel structure. Together, these transformations of the structure and phase composition of the material have led to a multiple increase in the microhardness of the surface layer with a thickness of up to 1500 mm.
•It has been shown that a combined modification of the surface layer of Gr1J03502 steel, including plasma spraying of a powder coating of the Ni-Cr-B-Si system and the subsequent irradiation with an intense pulsed electron beam, leads to formation of boride (CrB, Fe2B), silicide (FeSi), and carbide (Cr7C3) particles of iron and chromium.•Moreover, formation of an island structure has been found in the molten surface layer after the crystallization.•The islands containing refractory inclusions are separated by regions having the structure of high-speed dendritic crystallization of the submicron-sized range•The thickness of the total hardened layer, the microhardness of which is 4.6-6.5 times greater than the microhardness of the original steel, reaches 1500 μm.
The effect of the intensification of electron emission in a plasma-cathode diode with a grid-stabilized plasma boundary has been investigated. For a pulsed (100-mus) electron beam of 15-20-keV energy ...that passes through the plasma formed as a result of gas ionization by an electron beam, it has been revealed that an increase in pressure increases the emission current at a fixed plasma-cathode discharge current, and the emission current can become greater in magnitude than the discharge current. It has been shown that a significant increase in electron-beam current is provided by the secondary ion-electron emission that results from the bombardment of the emission electrode surface by the accelerated ions coming from the boundary of the anode plasma.
A method for finishing the surface of metal materials manufactured by additive technologies with an intense pulsed electron beam, which can be an alternative to traditional processing methods, is ...presented. The optimal irradiation modes for VT6 titanium alloy specimens manufactured by metal powder fusion and 308LSi stainless steel specimens manufactured by electron beam welding are determined. It is shown that the presented processing method leads to a visual decrease in the porosity and a multiple decrease in the surface layer roughness (R
a
) (by 20 times) of the VT6 titanium alloy manufactured by the additive method. The surface roughness of 308LSi stainless steel specimens manufactured by electron beam welding decreased by a factor of 2.1 in the longitudinal direction and by a factor of 5.2 in the transverse direction relative to the surfacing plane. It has been shown that the elemental composition, strength, and tribological properties of the specimens do not change after irradiation in optimal modes. Tensile testing of irradiated specimens revealed an increase in the tensile strength by 12% and in the ductility by 10% (VT6) and the anisotropy of the mechanical properties depending on the direction of tension relative to the surfacing plane (308LSi).
Abstract
Hypereutectic silumins have many positive properties - low density, high specific strength and corrosion resistance. They are non-magnetic, retain their strength at low, up to cryogenic ...temperatures, have a relatively low thermal expansion coefficient, high modulus of elasticity, increased wear resistance in friction pairs, etc. The structure of hypereutectic silumin is formed by a plastic eutectic matrix and brittle primary silicon crystals larger than 100 urn, and also contains crystals of aluminides of iron, copper, titanium and zirconium. Silumin of hypereutectic (18 wt% Si) composition was modified by irradiating the specimens by an intense pulsed electron beam. It was found that irradiation of hypereutectic silumin with an electron beam leads to a significant decrease in the number of micropores, the formation of a structure of high-speed cellular crystallization.
The surface of a porous tungsten carbide pseudo-alloy of the WC–WCoNiFe system has been modified by a pulsed electron beam and the method of combined electron-ion-plasma processing, which includes ...vacuum arc deposition of the VT1-0 titanium alloy film (1 μm) and subsequent pulsed electron-beam processing of the coating/substrate system. Optimal modes of pulsed electron-beam processing were found depending on the energy density in the pulse (40−65 J/cm
2
) and the pulse duration (150−200 μs). It is shown that the electron-beam surface processing of the material of this class under optimal conditions of electron-beam processing makes it possible to increase the microhardness of the surface layer by 15% compared to that of the initial material. Using methods of x-ray phase analysis, it was revealed that the increase in the microhardness was due to the formation of the W
2
C phase in the surface layer and the decrease in the amount of the binder (WCoNiFe). It is concluded that the combined electron-ion-plasma processing of the porous tungsten carbide pseudo-alloy of the WC–WCoNiFe system makes it possible to form a modified layer with a minimum number of pores and cracks on the surface.
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