Current Pulsed Electron Beam Irradiation Research Articles

Microstructures and improved properties of Cu–Mo alloys induced by high current pulsed electron beam irradiation

In this paper, a Cu–Mo alloying layer with improved properties was fabricated by high current pulsed electron beam (HCPEB) irradiation. The microstructure of the modified layer was investigated by x-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The microhardness and friction properties were also measured. After HCPEB irradiation, nano Mo particles, solid solution, and long-period superlattice structures were generated on the surface of Cu–Mo alloys, together with the formation of defect structures. These microstructures led to a significant increase in the surface hardness. The results of sliding wear tests indicated that the HCPEB-irradiated samples exhibited better properties compared with the initial one, which was attributed to the ultrafine Mo particles and the hardened surface.

Improved mechanical and tribological properties of TiAlN coatings by high current pulsed electron beam irradiation

High current pulsed electron beam (HCPEB) irradiation is an important surface engineering technique, which has been proved to be valid in modifying the surface microstructure and properties of various materials. In this work, HCPEB was employed to irradiate TiAlN coatings. The microstructure, mechanical and tribological properties of both original and irradiated TiAlN coatings were investigated. The results showed that the surface roughness of the TiAlN coatings first increased with 5 pulses of HCPEB irradiation, and then gradually declined with a further increase in pulse numbers. Compared with the original coating, the coating irradiated by 15 pulses demonstrated superior hardness (up to 33.4 GPa) and adhesion strength (112N), excellent wear resistance (wear rate of 3.3 × 10−6 mm3/Nm) and low friction coefficient (0.37). It is believed that the grain refinement, formation of the transition zone and adjustment of residual stresses after 15 pulses of HCPEB treatment are responsible for the improvement in both mechanical and tribological properties of the TiAlN coatings. These findings might suggest the potential applications of HCPEB irradiation for surface modification and hardness improvement of hard nitride coatings.

Enhanced surface quality and properties of cold spray Al coating by high current pulsed electron beam treatment

In this paper, high current pulsed electron beam (HCPEB) irradiation was employed to improve the surface density and properties of cold spray Al coating. The effects of the energy density on the microstructure, phase composition, stress, microhardness, wear, and corrosion behavior of coatings as-fabricated were investigated. HCPEB remelting treatment has improved the surface defects of cold spray coatings. The microhardness of treated coatings is higher than that of untreated coating, and the highest microhardness of the treated coatings occurs in the subsurface layer of the coatings. The wear track width and depth of the treated coating were lower than those of the untreated sample. The corrosion potential of the treated samples increases from −1.12 v to −0.95 v, and the corrosion current density reduces from 15.64 µA/cm2 to 3.31 µA/cm2. Our results demonstrated the wear and corrosion resistance of the cold spraying Al coating were dramatically improved by HCPEB irradiation.

Evolution of morphology, microstructure and phase composition of zirconia thin coating on copper as a result of low energy high current pulsed electron beam irradiation

Using X-ray diffraction, scanning and transmission electron microscopy we studied the evolution of the morphology, microstructure and phase composition in the near-surface layer of copper covered with thin (2.8 μm) ZrO2 coating induced by low-energy high-current pulsed electron beam irradiation (the surface energy density was in the interval of 5.0–18.0 J/cm2, the accelerating voltage was 30 kV, the pulse duration was 3.2 μs, the number of pulses was 10). The variation of adhesion of the coating to substrate was evaluated using scratch testing. The evaporation of the upper part of the coating during irradiation was found and the thickness of the coating nonlinearly decreased with the increase of the energy density. We discussed the reasons for the surface cracking taking into account microstructural changes in the near-surface layer of the material. The irradiation was found to transfer most of monoclinic ZrO2 phase in the as-deposited coating to tetragonal and, possibly, cubic one. The factors influencing the adhesive strength of the coating were revealed and a potential for the increase of adhesion was demonstrated. We showed that irradiation with enhanced surface energy density was required to obtain copper-based composite hardened with zirconia nanoparticles in the near-surface layer. The thickness of the composite layer may be as much as 6 μm.

Effects of WC grain size on surface hardening of WC-10Co cemented carbides by pulsed electron beam irradiation

Effects of primary WC size (DWC) in the surface enhancing of WC-Co cemented carbides by high current pulsed electron beam irradiation (HCPEBI) were studied in this work by investigating the morphological/microstructural evolution, phase transformations and the variation of microhardness of samples (Co: 10 wt %, DWC: ∼1.27 μm, ∼0.87 μm and ∼0.42 μm) treated with a range of HCPEBI shots under the energy density of 6 J/cm2. Results showed, with accumulating HCPEBI, the surface roughness of coarse-grained samples increased more significantly. The effects of DWC were more prominent in phase transformation and microstructure change under lesser irradiation. For samples with larger DWC, although the decomposition rate of WC in the top surface region was the lower, the amount of graphite precipitates prevailed overall. The maximum microhardness was also found in the irradiated coarse-grained (DWC = ∼1.27 μm) samples 3128.5 HV, showing a ∼80% increase from the initial state ∼1735.8 HV. Whereas for the fine-grained samples, surface microhardness gained a mere ∼29% increase after 35 shots.

Application of high current pulsed electron beam irradiation to smoothing of cold spray aluminum bronze coating

The aim of the work was investigation of the effect of high current pulsed electron beam irradiation (HCPEBI) with the energy density Es = 18 J/cm2, 20 pulses on the surface roughness, microstructure, phase composition and microhardness of the near-surface layer of aluminum bronze coating deposited on aluminum alloy using cold spray. Using SEM, line and 3D profilometry it was shown that HCPEBI in the used regime enabled smoothing of relief roughness of ∼50 μm in height. The content of free volume in the layer essentially decreased: there was very low number of small pores instead of big voids and delamination along the particles interfaces. Using XRD and TEM, formation of the ordered β1’ martensite of Cu3Al compound after HCPEBI was revealed. The microhardness of the layer decreased from 5.1 down to 2.2 GPa due to disappearance of the deformation-induced defects and phase transformation.

Enhancing mechanical and tribological properties of Ni3Al-15vol%TiC composite by high current pulsed electron beam irradiation

Effects of high current pulsed electron beam irradiation (HCPEBI) on the surface microstructure, mechanical properties, room and high temperature tribological behavior of the Ni3Al-15vol%TiC composite were investigated. The HCPEBI process refines the TiC particles down to nano scale and distributes them homogeneously throughout the modified layer. It also decreases grain size of the Ni3Al down to 400 nm. Grain refinement and homogeneous distribution of the TiC nanoparticles by irradiation process increase surface hardness from 538 HV0.025 to about 728 HV0.025. The HCPEBI process increases also the wear resistance of Ni3Al-15vol%TiC composite at both room temperature and elevated temperature of 600 °C due to the increasing hardness and roughening the surface of the sample. Adhesive wear was found to be the dominant wear mechanism for both as-received and irradiated samples at room temperature beside with the delamination. At the elevated temperature of 600 °C, oxidative wear and delamination of the oxide layers occur as the main wear mechanisms in the as-received sample. In the irradiated sample, on the other hand, wear starts with the abrasive wear with micro-cutting of surface hills of irradiated sample, and continues with oxidative and delamination wear mechanisms.

Fibrous nano composite reinforced surface on WC-Co cemented carbide achieved by pulsed electron beam irradiation and subsequent tempering

Exotic microstructures can be tailored by extreme conditions with combined material processing techniques for desirable properties. In this work, an innovative 2-staged process was explored for WC-10Co cemented carbide surface modification. Firstly, rapid thermal cycles were induced by high current pulsed electron beam (HCPEB) irradiation at energy density of 6 J/cm2, during which the micro-WC/Co was melted and re-solidified into a nano-scaled equiaxed grain microstructure with metastable fcc-WC1-x as the majority phase in the surface layer (~2 μm). Thereafter, a subsequent tempering process was applied to the HCPEB-irradiated cemented carbide specimens and the nano equiaxed grains in the surface layer were gradually transferred into nano-scaled fibrous microstructure. Phase transformation was investigated using thermo-gravimetric analysis differential scanning calorimetry (TGA-DSC), confocal laser scanning microscopy (CLSM), scanning electron microscopy (SEM) and X-ray diffractometry (XRD). Analysis showed that the fibrous nano structure resulted from the decomposition of WC1-x at 600-700 ºC via fcc-WC1-x → hex-WC + hcp-W2C. After the 2-staged process, the surface microhardness was greatly improved.

Microstructure and Properties of Mechanical Alloying Al-Zr Coating by High Current Pulsed Electron Beam Irradiation.

The “HOPE-I” type high-current pulsed electron beam (HCPEB) equipment was used to irradiate the pure aluminum material with Zr coating preset by ball milling to realize the alloying of a Zr–Al coating surface. The microstructure and phase analysis were conducted by XRD, SEM, and TEM. The experimental results show that after Zr alloying on the Al surface by HCPEB, a layer of 15 μm was formed on the surface of the sample, which was mainly composed of Zr and Al–Zr intermetallic compounds. A large number of Al3Zr (Ll2) particles was uniformly distributed in the alloyed layer, and the Al grains were obviously refined. In addition, the surface hardness and corrosion resistance of the samples were improved significantly after HCPEB irradiation.

Enhancing anti-wear and anti-corrosion performance of cold spraying aluminum coating by high current pulsed electron beam irradiation

High current pulsed electron beam (HCPEB) was employed to irradiate cold spraying aluminum coating. The microstructures, tribological and corrosion behaviors of the untreated and irradiated samples were investigated by the X-ray diffraction (XRD), scanning electron microscope (SEM), ball-disc wear and electrochemical tests. HCPEB irradiation significantly triggered the surface remelting and densification of the coating texture. Compared with the original coating, the irradiated coating showed a higher hardness of up to 88 HV, a higher compressive stress value of 31 MPa and a lower wear rate of 1.06 × 10−4 mm3 N−1 m−1, but also exhibited an outstanding anti-corrosion performance, reflected by a higher polarization resistance and a smaller corrosion current density of 4.45 μA/cm2. These current findings confirmed that HCPEB irradiation shows a huge potential for enhancing the anti-corrosion and anti-wear properties of cold spray coatings.

Structure and phase composition of “ZrO2 thin coating – aluminum substrate” system processed through pulsed electron beam irradiation

Using X-ray, scanning and transmission electron microscopy we studied the variation of the structure and phase composition in the near-surface layer of aluminum covered with thin ZrO2 coating induced by high current pulsed electron beam irradiation with the surface energy densities in the interval of 5.0–10.0 J/cm2. The irradiation with the low energy density is found to transfer monoclinic and tetragonal ZrO2 coating to cubic one. The depth of the remelted aluminum layer nonlinearly depends on the surface energy density. The different formation mechanism of ZrO2 nanoparticles in the near-surface layer for the different energy densities is revealed. Amorphous Al2O3 particles are shown to form on the surface of the irradiated samples due to substitution of zirconium by aluminum in the oxide.

Surface alloying of chromium/tungsten/stannum on pure nickel and theoretical analysis of strengthening mechanism

Surface alloying of chromium/tungsten/stannum on pure nickel were facilitated by high current pulsed electron beam (HCPEB) irradiation. The evolution of microstructure and microhardness of the irradiated surface were characterized. On the other hand, first-principles calculations, based on density functional theory (DFT), implemented in the Vienna Ab initio Simulation Package (VASP), were adopted to compute and simulate the solid solution mechanism of alloy element doping in matrix. From the simulation, the Sn atom resulted in the largest increase of lattice constant due to its largest atomic radius among three elements, and which Sn doping caused the strongest inter atomic force. Therefore, the VASP simulation indicated that Ni-Sn HCPEB irradiated sample has the highest hardness value among three different irradiated samples, which is good agreement with the experimental results obtained.

High Chrome Steel Modified by High-Current Pulsed Electron Beam

The paper presents the results of the structure and properties modification of 20Cr23Ni18 (AISI 310) high chrome austenitic stainless steel after the exposure to the low energy high current pulsed electron beam (LEHCPEB) irradiation. The AISI 310 is used to manufacture machine components and mechanisms operating at 1000–1050°С such as combustion chambers, turbine blades, and others. The SOLO plasma-ionassisted electron-beam setup (Institute of High Current Electronics SB RAS, Tomsk, Russia) is used for the steel treatment. The SOLO provides a low-pressure arc discharge with a grid-stabilized cathode plasma boundary and the open-boundary anode plasma. The electron-beam parameters include 18 keV energy; 20, 30 and 40 J/cm2 energy density; 50 and 200 μs pulse duration; the number of pulses – 3; 0.3 s–1 pulse frequency; ~0.02 Pa gas (argon) pressure in the process chamber. Scanning and transmission electron microscopies and the X-ray diffraction analysis are used to investigate the structure and phase composition of the steel, microhardness and wear resistance being regarded as the steel properties. It is shown that the exposure of the AISI 310 to high-current pulsed electron beam results in a high-speed melting of the surface layer, creates the crystallized cellular structure of submicron size, and enhances the wear resistance by 8 times.

Structure and Properties of Silumin Surface after Vacuum Arc Plasma-Assisted Deposition of Coatings Irradiated by Low Energy High Current Pulsed Electron Beam

The paper presents the results of modification of the silumin surface layer using a multicycle processing technique which combines the formation of the film (titanium)-substrate (silumin) system and the low energy high current pulsed electron beam (LEHCPEB) irradiation of submillisecond duration in one cycle. A KOMPLEX plasma-ion-assisted electron-beam setup (Institute of High Current Electronics SB RAS, Tomsk, Russia) is used for silumin treatment. Titanium is used as an alloying element. The thickness of the deposited film is 0.5 μm in each alloying cycle, the number of which is 1, 5 and 10. Surface alloying includes ion-bombardment cleaning and heating by hot and hollow cathodes of argon plasma discharge, with negative bias voltage supply to the specimen (initial heating up to preset temperature, surface cleaning and activation); plasma-enhanced chemical vapor deposition of metal films (argon is used as a carrier gas); and LEHCPEB irradiation of the film (titanium)-substrate (silumin) system. It is shown that multicycle alloying of the grade АK12 silumin (G-AlSi12, DIN, Germany) with titanium leads to a dissolution of silicon and intermetallic inclusions in the surface layer up to 30 μm thick, the formation of submicro- and nanocrystalline multiphase structure with the microhardness and wear resistance, which are 1.4 and 14.2 times higher than in cast silumin.

Thermal stability of modified surface microstructure on WC-Co cemented carbide after high current pulsed electron beam irradiation

Investigation on the thermal stability of the modified surface microstructure on WC-Co cemented carbide after high current pulsed electron beam (HCPEB) irradiation was carried out. Microstructural analysis showed that the micro-WC grains were melted and a compact microstructure was formed in the surface layer. Nano-grained cubic phase WC1-x was identified as the predominant phase in the modified layer, resulted from HCPEB-induced superfast heating, melting and re-solidification cycles. The modified specimens were subjected to annealing process at varied temperatures in an Ar ambience for 1 h. Post-annealing microstructural inspection results revealed that the modified microstructure was stable when the annealing temperature did not exceed 500 °C. When the annealing temperature was elevated to 600–700 °C, the cubic phase WC1-x gradually transferred into two hexagonal phases, WC and W2C. Further elevating the annealing temperature up to 900 °C, significant amount of ternary phases, Co6W6C and Co2W4C, formed in the surface layer. The evaluation of surface microhardness indicated a strengthening effect of the annealing on the modified microstructure. The maximum microhardness (2530 HV) was obtained after annealing at 700 °C.

The surface modification of aluminum by mechanical milling of Pb coating and high current pulsed electron beam irradiation

This paper reports the surface morphology and properties of Al substrates with Pb coating, which was deposited by mechanical milling and then treated by high current pulsed electron beam (HCPEB) irradiation. After HCPEB irradiation treatment, some previously formed defects such as micro-pits, craters, and bulged nodules were eliminated, resulting in significant reduction of surface roughness of initial Pb/Al sample, and the formation of a dense and adherent Pb/Al alloying layer. Notably, when the number of irradiation pulses reached 30, there was uniform distributions of Pb in the mixture of Pb and Al elements in the milled samples, which resulted in the formation of gray layers with thickness of 12 μm (milling for 1 h) and 8 μm (milling for 2 h). These formed layers effectively improved the wear resistance. Moreover, the hardness of Pb/Al sample also improved after HCPEB irradiation due to structure defect strengthening and ultra-fine Pb-rich particles reinforcement. The above results demonstrate that HCPEB treatment is an effective method to obtain high-quality alloy coating layer, resulting in the formation of an excellent alloy.

The effect of high current pulsed electron beam irradiation on microstructure and properties Cu-Fe powder metallurgical alloys

In this paper, Cu-Fe powder metallurgical alloys were firstly fabricated, and a innovative surface modification technique, high current pulsed electron beam (HCPEB), was then irradiated these Cu-Fe alloys with 5 and 10 pulses. The morphologies, microstructure and mechanical properties of the specimens both before and after HCPEB irradiation were studied. The morphologies revealed that the surface of 5-pulsed sample was melted completely, and a large amount of craters were formed. Those craters were eliminated and fused by the subsequent 10-pulsed HCPEB processing. Besides, the distribution of Fe element was fairly homogenous on the irradiated surface. Additionally, the modified microstructures consisted of refined Cu sub-grains, tiny Fe particles, Cu (Fe) solid solution and abundant defects, which played an important role in the improvement of microhardness. The HCPEB irradiated Cu-Fe samples possessed better wear resistance which was ascribed to the reduction of roughness, enhancement of hardness, and formation of lubricating film.

Surface microstructures and high-temperature high-pressure corrosion behavior of N18 zirconium alloy induced by high current pulsed electron beam irradiation

The aim of present paper was to study the microstructural evolution and the high-temperature high-pressure corrosion behavior of N18 zirconium alloy prior and after high-current pulsed electron beam (HCPEB) surface irradiation. Observations of microstructures showed that after HCPEB irradiation, the surface layer of the sample was melted, inside which gradually refined grains, martensites and their internal twin substructures were obtained. Meanwhile, second-phase particles (SPPs) were dissolved into the matrix within the modified layer, and alloying elements Fe, Cr, Nb were supersaturated in Zr-based solid solution. Besides, high residual compressive stress was unceasingly accumulated in the surface layer with the increasing of pulses. After exposed at 500 °C/10.3 MPa superheated steam for 30 days, the corrosion resistance of multiple-pulsed samples, particularly the 25-pulsed one, was obviously higher than that of the initial sample. The combined action of high residual compressive stress, supersaturated alloying elements, selective purification effect and abundant structure defects in the modified layer helped improve the corrosion resistance.

Formation mechanism of graphite nanospheres in W-C-Co system under high current pulsed electron beam irradiation

Understanding the formation mechanism of graphite nanospheres (GNS) in W-C-Co system under high current pulsed electron beam (HCPEB) irradiation is necessary for its application on surface modification of WC-Co cemented carbide. With this aim, XRD, SEM, EDS and TEM were used to investigate the effect of HCPEB irradiation on surface microstructure and phase composition. Results showed the micro-WC grains and Co were melted and transformed into nano-grained composite structure in the surface layer ∼1.29 μm. Two general scales of GNS were discerned in two types of element composition ambiences, i.e. ∼100 nm in Co-rich region and ∼50 nm in Co-poor region. Thermodynamic analysis suggested that they were the results of different routes in the non-equilibrium melting and re-solidification process.

Surface composite microstructure and improved mechanical property of YG10X cemented carbide induced by high current pulsed electron beam irradiation

The surface microstructure evolution and its effect on mechanical property was systematically investigated for YG10X cemented carbide irradiated by high current pulsed electron beam (HCPEB) with a steady energy density of 6 J/cm2 and different pulse numbers. The surface morphology was characterized by optical microscopy (OM), three-dimensional laser scanning microscopy (LSM) and scanning electron microscopy (SEM); and energy dispersive spectrometry (EDS) and X-ray diffractometry (XRD) was carried out to reveal the elemental profile and phase transformation under HCPEB irradiation. During the HCPEB-induced rapid re-melting and re-solidification process, the redistribution of chemical elements, grain refinement and phase transformation WC(hex) → graphite + β-WC1-x(fcc) occurred. Moreover, the preferential precipitation of nano-grained graphite in the Co-rich region of melt pool was discovered. The drastic structural change led to a maximum ~34% increment of the initial state in microhardness and about a two third reduction in friction coefficient.