High Current Pulsed Electron Beam Treatment Research Articles

Microstructure and Properties of TiN/TiCN/Al2O3/TiN Coating Enhanced by High-Current Pulsed Electron Beam

In this work, a TiN/TiCN/Al2O3/TiN coating deposited onto cemented carbide matrix by chemical vapor deposition was irradiated by high-current pulsed electron beam (HCPEB). The influence of pulse times on the phase composition, microstructure, and mechanical properties of the coating investigated. The results showed that no new phase was produced, the grain size of the coating surface was refined, the surface became flat, and the surface roughness decreased after HCPEB treatment. The TiN/TiCN/Al2O3/TiN coating presented a smooth surface with good mechanical performance after HCPEB. A maximum hardness was obtained after 15 pulses, and the 15-pulse irradiated coating showed better wear resistance. The improvement in the coating’s performance after irradiation was mainly attributed to the formation of grain refinement and crystal defects, as well as the change of stress field inside the coating. The objective of this study was to evaluate the potential of HCPEB modification in the preparation of high-performance coating by analyzing the microstructure and property of coating under different pulses.

Effect of high current pulsed electron beam on surface microstructure and properties of cold-rolled austenitic stainless steel

High current pulsed electron beam (HCPEB) was used to modify the surface microstructure and performance of AISI 304 stainless steel with different cold-rolling deformation. The phase, microstructure, microhardness, and corrosion performance were characterized and analyzed after cold-rolling and HCPEB treatment. The results show that after cold-rolling, deformation-induced martensites (DMs) are generated in the deformation twin lamellae or at the intersections of multiple twin lamellae, resulting in a grid-like morphology, smaller size, and a certain orientation relationship with the parent austenite. The content of DMs increases with increasing cold-rolling deformation. After HCPEB treatment, many craters with different sizes and similar densities are produced on the sample surface, and the DMs are transformed into austenite again in the surface layer. The difference is that the grain size of the regenerated austenite after HCPEB is much smaller than that of the initial austenite (before cold-rolling). Such high-density equiaxed ultrafine grains (UFGs) of austenite formed after HCPEB present a twin feature, which is the inheritance of the orientation relationship between DMs and austenite formed during rolling. HCPEB treatment can effectively reshape the phase and microstructure of the surface layer of the cold-rolled deformed austenitic steel but reduce the surface hardness and increase pitting corrosion tendency.

Hot corrosion behavior of NiCoCrAlYSi laser cladding coating modified using high-current pulsed electron beam in different corrosive salt environments

The investigation focused on microstructural changes and hot corrosion behavior in various salt environments (Na2SO4 + 25 wt% K2SO4 and Na2SO4 + 25 wt% NaCl) at 900 °C of NiCoCrAlYSi laser cladding coatings before and after high-current pulsed electron beam (HCPEB) irradiation. HCPEB treatment effectively eliminated imperfections like micropores and segregation of the components, creating a remelted layer with high-density dislocations and nanostructure. The irradiated impacts including polishing, purification, composition homogenization, and grain refinement facilitated the development and self-repair of a compact and tenacious oxide scale. This enhanced oxide layer effectively mitigates extensive corrosive media erosion. The utilization of HCPEB treatment has shown significant potential in enhancing the hot corrosion resistance of NiCoCrAlYSi laser claddings.

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.

Microstructural evolution of thermally grown oxide of an arc ion plated MCrAlX coatings after high-current pulsed electron beam treatment

An arc ion-plated NiCoCrAlYHfSi coating modified by a high-current pulsed electron beam (HCPEB) was examined in this study. The dynamic growth behavior and formation mechanisms of the thermally grown oxide (TGO) of the original and modified coatings were thoroughly compared by isothermal oxidation at 1050 °C. HCPEB irradiation led to the transformation of the rough original coating into a flat, smooth, and dense structure. Furthermore, Y-Al nanoparticles and high density of dislocations were also obtained in the modified layer. These modification characteristics can establish favorable conditions for the rapid accumulation and stable growth of the protective Al2O3 particles. With the extension of oxidation time, the CrO3 formed in the oxide film left many small pits after volatilization, but these pits were filled with Al2O3 particles. Compared with the oxide film of the original coating, the TGO of the modified coating is flat, continuous, and dense, and its growth rate is notably slower. Also, the growth of Ni, Cr, and Co rich oxides was expectantly restrained. Obviously, the HCEPB technique has the capacity to change the growth behavior of the TGO and significantly enhance the coating's resistance to high-temperature oxidation.

Effect of High Current Pulsed Electron Beam (HCPEB) on the Organization and Wear Resistance of CeO2-Modified Al-20SiC Composites.

This paper investigates the joint effect of high current pulsed electron beam (HCPEB) and denaturant CeO2 on improving the microstructure and properties of Al-20SiC composites prepared by powder metallurgy. Grazing Incidence X-ray Diffraction (GIXRD) results indicate the selective orientation of aluminum grains, with Al(111) crystal faces showing selective orientation after HCPEB treatment. Casting defects of powder metallurgy were eliminated by the addition of CeO2. Scanning electron microscopy (SEM) results reveal a more uniform distribution of hard points on the surface of HCPEB-treated Al-20SiC-0.3CeO2 composites. Microhardness and wear resistance of the Al-20SiC-0.3CeO2 composites were better than those of the Al matrix without CeO2 addition at the same number of pulses. Sliding friction tests indicate that the improvement of wear resistance is attributed to the uniform dispersion of hard points and the improvement of microstructure on the surface of the matrix after HCPEB irradiation. Overall, this study demonstrates the potential of HCPEB and CeO2 to enhance the performance of Al-20SiC composites.

Improved wear resistance of cemented carbide impact needle under high frequency micro-amplitude impact treated by high current pulsed electron beam

Assembly and packaging technology is one of the most critical factors that restrict the development of microelectromechanical systems (MEMS), including chips and other devices. Dispensing robot is a key high-end equipment in MEMS packaging. Its core component, WC-Co impact needle, is limited by fretting wear and deformation, leading to reduced service accuracy and life, which is the most important cause of failure. Impact fretting wear frequently occurs in micro-nano mechanical systems and has been widely studied. However, the combined high frequency (∼300 HZ) and micro impact amplitude (∼120 μm) wear behaviors such as WC-Co impact needle with ultrafine grain (∼100 nm) is rarely concerned. To further understand the influence of impact frequency and impact velocity on the wear rate of impact needle, dispensing experiments were designed and the wear mechanism was investigated. Results indicated that the impact velocity has more influence on the wear rate of impact needle than the impact frequency. In addition, a high-current pulsed electron beam (HCPEB) surface treatment method which can effectively increase the wear resistance of impact needle was proposed. After HCPEB treatment, the abrasion loss was reduced by 44% compared to the untreated one at the same impact frequency and different impact velocities, while the abrasion loss was reduced by 52% compared to the untreated one at the same impact velocity and different frequencies. These can be attributed to the fact that HCPEB treatment decreased the grain size of WC-Co cemented carbide impact needle and promoted WC phase transition, leading to an increase in microhardness.

Effect of high-current pulsed electron beam treatment on defect substructure of the high-entropy alloy of Co – Cr – Fe – Mn – Ni system

High-current pulsed electron beam surface treatment is a method of materials modifying, which improves the mechanical properties of metal materials. Due to high-speed heating, evaporation, recrystallization, as well as plastic deformation, dislocations with high density are formed in the surface and, as a result, an increase in indicators of various physical and mechanical properties, such as hardness, wear resistance, etc., is observed. Since currently high-entropy alloys are a relatively new class of materials, the effect of pulsed electron beam treatment on the dislocation substructure has not yet been established. In this work, a non-equiatomic high–entropy alloy of the Co – Cr – Fe – Mn – Ni system, made using a wire-arc additive manufacturing, was subjected to surface treatment using a high-current pulsed electron beam with an energy density of 30 J/cm2. By the method of studying thin foils using transmission electron microscopy, it was found that the treatment does not affect the chemical composition of the alloy, but leads to serious changes in the dislocation substructure. A nonmonotonic change in the scalar density of dislocations was revealed, reaching a maximum value of 5.5·1010 cm–2 at a distance of 25 µm from the irradiation surface. It is shown that an undirected cellular dislocation substructure with cell sizes from 400 nm to 600 nm is formed at this distance from the surface. With further distance from the surface at a distance of up to 45 µm, the dislocation substructure changes from cellular to cellular-mesh. At a distance of 120 – 130 µm, the effect of a high-current pulsed electron beam is not observed – the substructure corresponds to the substructure of the initial alloy with a chaotic distribution of dislocations.

Surface microstructure evolution mechanism of WC-Co hard alloy treated by high current pulsed electron beam

The surface of WC-Co hard alloy was modified treatment by high current pulsed electron beam (HCPEB). The surface microstructure evolution mechanism of WC-Co hard alloy was characterized by XRD, SEM, EBSD, and TEM, respectively. The temperature distribution of WC-Co hard alloy during HCPEB treatment process was calculated and discussed. The results show that rapid melting and rapid solidification induced by HCPEB caused the phase transformation and the microstructure evolution on the surface of the hard alloy, and when irradiation times was 13th times, the microcracks and voids on the WC-Co hard alloy surface were gradually healed by remelting repeatedly, causing the formation of dense nanostructures. The microhardness of the modified specimen surface layer by 13th irradiation increased to 1159.0 HV, and the wear resistance increased to 1.72 times that of the matrix. The strength and wear resistance of the surface layer of the specimen were improved due to the refinement of WC grains, the forming of WC1-X nanophase, and the precipitation of nanographite particles. The microstructure evolution mechanism on the alloy surface after the modified treatment was proposed that a metastable equilibrium system was formed (WC + WC1-X + Co3W9C4+graphite phase).

Comparison of microstructure and oxidation behavior of NiCoCrAlYSi laser cladding coating before and after high-current pulsed electron beam modification

In this study, NiCoCrAlYSi coatings prepared via laser cladding were modified using a high-current pulsed electron beam (HCPEB) technique. The microstructural modifications and the effects that the HCPEB treatment had on the high-temperature oxidation resistance were investigated. Microstructural observations reveal that the cladding coating surface, which was initially porous and composed of dendritic segregations, was totally changed after HCPEB irradiation; specifically, the microstructure became rather dense, and the composition became uniform. The grain refinement and high density of dislocations were obtained in the remelted layer. After oxidation for 100 h, the original coating showed relatively poor oxidation resistance, presented as severe internal oxidation. After HCPEB irradiation, the modified coating samples promoted the rapid formation of a stable, continuous, and slow-growing α-Al2O3 scale, which effectively prolonged the high-temperature life of the cladding coating.

Preparation and Electron-Beam Surface Modification of Novel TiNi Material for Medical Applications

A new approach to fabricate TiNi surfaces combining the advantages of both monolithic and porous materials for implants is used in this work. New materials were obtained by depositing a porous TiNi powder onto monolithic TiNi plates followed by sintering at 1200 °C. Then, further modification of the material surface with a high-current-pulsed electron beam (HCPEB) was carried out. Three materials obtained (one after sintering and two after subsequent beam treatment by 30 pulses with different pulse energy) were studied by XRD, SEM, EDX, surface profilometry, and by means of electrochemical measurements, including OCP and EIS. Structural and compositional changes caused by HCPEB treatment were investigated. Surface properties of the samples during their storage in saline for 10 days were studied and a model experiment with cell growth (MCF-7) was carried out for the unmodified sample with an electron beam to detect cell appearance on different surface locations.

Microstructural modifications and high-temperature oxidation resistance of arc ion plated NiCoCrAlYSiHf coating via high-current pulsed electron beam

A NiCoCrAlYSiHf coating prepared via arc ion plating was irradiated using a high-current pulsed electron beam (HCPEB) technique. The self-quenching and polishing effect induced by HCPEB treatment normalized the defects, re-melted the surface, refined the grains, introduced the dislocations, and changed the elemental distributions. After oxidation for 200 h, severe spalling of the oxide scale and internal oxidation occurred in the original coating. The restructuring of the remelted layer contributed to a very stable, continuous, slow-growing, and uniform α-Al2O3 scale during the entire oxidation stage. HCPEB technique is an effective way to dramatically improve the service life of an MCrAlYX-type coating.

Evolution of Microstructure at the Surface of 40CrNiMo7 Steel Treated by High-Current Pulsed Electron Beam

High current pulsed electron beam (HCPEB) has recently been developed as an effective technique of material surface modification. In this research, a self-developed HCPEB equipment (HOPE-I) was adopted to perform surface modification on quenched and tempered 40CrNiMo7 steel. A composite nanometer structure was formed on the modified surface layer, and the martensite transformation and the dissolution and fracture of cementite can be observed. After initial irradiation, the high cooling rate caused the formation of nanocrystalline on the surface. With continuous irradiation treatments, the cooling rate gradually reduced, while the carbon kept dissolving and ended with surface composition homogenization. Both competitive factors result in the evolution rule of nanometer dimensions of surface structure. After HCPEB treatment, the average size of austenite phase on the modified surface decreased from micron-sized to nanoscale. The corrosion rate decreased from 0.12 mm/a to 0.02 mm/a, showing remarkable improvement of corrosion resistance. The main factors of the improvements of corrosion resistance property are the flat, dense structured and preferred crystal orientation on the modification layer of the treated material surface.

Surface modifications of a hyperperitectic Zn-10 wt% Cu alloy by pulsed electron beam treatment

The aim of the present work is to study the effect of High Current Pulsed Electron Beam (HCPEB) treatments on the surface microstructure and properties of a hyperperitectic Zn-10 wt% Cu alloy. The alloy samples are treated by HCPEB with an accelerating voltage of 25 kV, an energy density of 4 J/cm2, a pulse duration of 1.5 μs and pulse numbers of 5 and 15. The surface microstructure, phase components and compositions are characterized by using optical microscopy (OM), X-ray diffraction (XRD), energy dispersive spectroscopy (EDS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Due to the rapid solidification and cooling occurred after pulsed electron beam irradiation, the peritectic reaction ε-CuZn5 + L → η-Zn is suppressed, leading to the increased content of ε-CuZn5 in the surface resolidified layer. The polarization tests in the 3.5 wt% NaCl water solution and microhardness measurements show that the corrosion resistance is improved and microhardness increases after HCPEB treatments. In particular, the 5 pulsed Zn-10 wt% Cu alloy sample exhibits the best corrosion resistance due to the chemical homogenization, microstructure refinement and the formation of lower density of craters in the surface layer.

Surface microstructure modifications and in-vitro corrosion resistance improvement of a WE43 Mg alloy treated by pulsed electron beams

In the present study, the surface microstructures and in-vitro corrosion resistance of an as-cast WE43 Mg alloy after high current pulsed electron beam (HCPEB) treatments are investigated. It is shown that the surface presents craters and wavy morphology after HCPEB treatments, which are the typical characteristics of the morphology after rapid melting and cooling. The initially existed Mg14Nd2(Y,Gd) particles are dissolved, and the fine β՛ (c-bco, a = 0.64 nm, b = 2.223 nm and c = 0.521 nm) precipitates are formed and homogeneously dispersed in the treated layer. The electrochemical measurements in the simulated body fluid (SBF) show that the corrosion current density (Icorr) of the 15 pulsed sample (2.66 × 10−5 A cm−2) is reduced by an order of magnitude compared to that of the untreated sample (1.91 × 10−4 A cm−2), and the polarization resistance (Rp) is increased by 176.9%. The disappearance of second phase, the formation of homogeneous dispersed β՛ nano-precipitates and the chemically homogenized melted layer account for the improved corrosion resistance of the 15 pulsed WE43 sample in SBF.

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.

Surface modification of CrFeCoNiMo high entropy alloy induced by high-current pulsed electron beam

The surface of non-equiatomic CrFeCoNiMo high entropy alloy (HEA) was irradiated by high-current pulsed electron beam (HCPEB). Microstructure, mechanical properties and corrosion resistance of the CrFeCoNiMo HEA before and after HCPEB irradiation were studied systematically. The results of XRD analysis indicated that the surface of the irradiated samples exhibited preferential orientation on (1 1 1) and (2 0 0). Microstructure observations revealed that a compact remelted layer was formed on the surface of the alloy after HCPEB irradiation, the thickness of the remelted layer rose as the increase of pulse numbers. Besides, numerous nano σ particles, nanocrystallites with an average size about 109 nm and abundant deformed structures also appeared in the remelted layer. The mechanical properties of CrFeCoNiMo alloy were significantly enhanced after HCPEB treatment, which was mainly ascribed to intense plastic deformation via stress, sub-grain strengthening along with precipitation hardening. Electrochemical results demonstrated that all the irradiated specimens had a positive potential and a lower current density in 3.5 wt% NaCl solution compared with the untreated sample. The homogenized surface and the efficient eliminating of the local concentration of Cr element jointly contributed to the improvement of corrosion resistance.

Formation of a Double-Layer Ultrafine Crystal Structure for High-Current Pulsed Electron Beam-Treated Al–20Si–5Mg Alloy

In this paper, the effect of high-current pulsed electron beam (HCPEB) on the microstructure refinement of an Al–20Si–5Mg alloy in the cross-section modified zone was studied, and a double-layer ultrafine crystal structure of the Al–20Si–5Mg alloy was formed. It was found that the cross-section modified zone was divided into three zones, namely, the remelted layer, the heat-affected zone, and the thermal stress wave-affected zone after HCPEB treatment. For the remelted layer, metastable structures were formed due to the rapid heating and cooling rates. For the heat-affected zone, the grain of the aluminum phase was refined due to the cooperative effects of shock wave (formed during an eruption event of the brittle phase), thermal-stress wave (formed during thermal expansion of the alloy surface), and quasi-static thermal stress (formed as a result of an unevenly distributed temperature gradient in the inner material) at high temperatures. For the thermal stress wave-affected zone, the grain refinement was not obvious due to the decreasing energy of the shock wave and the thermal-stress wave at low temperatures. In addition, firm evidence for the tracing of shock waves in the heat-affected zone was demonstrated for the first time and verified for the founding of the broken acicular eutectic silicon. Through this experiment, the mechanical properties of Al–20Si–5Mg alloy materials in both the remelted layer and heat-affected zone were significantly improved after HCPEB treatment.

Structural decomposition and phase changes in TiNi surface layer modified by low-energy high-current pulsed electron beam

The TiNi shape memory alloy was exposed to low-energy high-current pulsed electron beam treatment with surface melting at an energy density Es = 10 J/cm2, pulse duration τ = 20 μs and number of pulses n = 1, 10, 25. The structure and phase state of modified surface layer of TiNi were analyzed in detail by methods of AES, XRD and TEM/EDS/SAED in cross-section geometry. It was established that modified TiNi surface region reveals three layers: upper layer 1 of thickness 5–7 nm which comprises TiO2 and Ti3Ni4 nanoparticles, layer 2 of thickness 1.5–5 μm with a columnar B2 structure stabilized by TiO2 and Ti3Ni4 nanoparticles, and layer 3 of thickness up to 10 μm which is represented by B2 structure with a high dislocation density and strain-induced B19′ martensite. It was considered how the number of pulses at a constant energy density influences its structural characteristics, and discuss the role of oxygen in stabilizing the columnar structure of its melted and rapidly solidified surface layer.

Surface microstructure and property modifications in a Mg-8Gd-3Y-0.5Zr magnesium alloy treated by high current pulsed electron beam

In the present study, the effect of high current pulsed electron beam (HCPEB) surface treatments on the microstructure, composition, stress states and properties of a Mg-8Gd-3Y-0.5Zr alloy has been investigated. The surface layers showed different features in microstructure and residual stress states under different number of pulses. Such a variation is essentially due to the different level of the dissolution of β-Mg5(Gd,Y) particles in remelted layers and the impact from thermal stresses generated by HCPEB treatments. The results have shown that, after 5 pulses of HCPEB treatment, maximum hardness in the surface layer of the sample was increased by 35% and the corrosion rate in 3.5 wt% NaCl water solution was reduced by 30% as compared with those of the untreated sample. The formation of nano structured cells of Mg-RE solid solution and β-Mg5(Gd,Y) nano precipitates, together with the residual compressive stress in the surface layer of the 5 pulsed sample account for the increased microhardness and improved corrosion resistance of the HCPEB treated Mg-8Gd-3Y-0.5Zr Mg alloy.