Electron Beam Surface Treatment Research Articles

Grain Refinement and Hardening Induced by Heavy Deformation Using Low Energy High Current Pulsed Electron Beam Surface Treatment

The low energy high current pulse electron beam (LEHCPEB) irradiation induces ultra fast dynamic temperature fields in the surface of the material to which is associated dynamic stress fields that causes intense deformation at the material surface and sub-surface. Improved surface properties (hardness, corrosion resistance) can be obtained using the LEHCPEB treatment. Under the “Melting” mode, the top surface (few µm) which is melted and rapidly solidified (107 K/s), can solidify has nano-domains formed from the highly under-cooled melt. The thermal stress wave that propagates in the sub-surface imposes strain hardening and grain size refinement. This induces a sub-surface hardening that can extent over about 100 µm. The use of the “Heating” mode is less conventional. This mode can promote grain size refinement, hardening as well as texture modification without modification of the sample geometry.

Mechanisms of hardening, wear and corrosion improvement of 316 L stainless steel by low energy high current pulsed electron beam surface treatment

The mechanisms of corrosion and wear improvements by low energy high current pulsed electron beam (LEHCPEB) have been investigated for an AISI 316 L steel. Selective purification followed by epitaxial growth occurred in the top surface melted layer (2–3 μm thick) that was softened by tensile stresses and, to a much lower extent, by lower efficiency of MnS precipitation hardening. Electrochemical impedance spectroscopy and potentiodynamic polarization analyses used to model the corrosion behavior revealed that, while craters initiated at MnS inclusions initially served as pitting sites, the resistance was increased by 3 orders of magnitude after sufficient number of pulses by the formation of a homogeneous covering layer. The wear resistance was effectively improved by sub-surface (over 100 μm) work hardening associated with the combine effect of the quasi-static thermal stress and the thermal stress waves. The overall results demonstrate the potential of the LEHCPEB technique for improving concomitantly the corrosion and wear performances of metallic materials.

Friction and wear behaviour of electron beam surface treated aluminium alloys AlSi10Mg(Cu) and AlSi35

Abstract Because of their low density, Al based materials are increasingly used for state-of-the-art lightweight construction solutions. With regard to systems subjected to wear, Al alloys cannot be used for highly stressed components, unless they have been made resistant against wear by additional measures such as surface treatment. Electron beam (EB) surface treatment offers a possibility for producing hard wear-resistant layers on components made of Al alloys. Concerning Al materials, distinct improvements of layer properties can be achieved exclusively by the use of liquid phase surface processes (remelting, alloying, dispersing and cladding). The paper deals with current results of investigations in the field of EB surface remelting and alloying technologies of cast alloy AlSi10Mg(Cu) and spray-formed alloy AlSi35. The EB surface treatment of these alloys causes significant changes of properties in surface layers with depths of 0.5–4.0 mm basing on a local modification of microstructure. The hardness and scratch energy density of surface layers are 2–7 times higher than those of the base materials. Moreover, studies on friction and wear behavior under oil lubricated conditions at 80 °C impressively demonstrate the upgraded surface layer properties. Depending on the type of EB-alloying additives (Co, Cu, Ni powder) the specific wear rate decreases by a factor of 10–50 by effectuating a lower coefficient of friction simultaneously. The technologies discussed give a picture of the potential of EB technologies and offer new possibilities for improving service life and reliability of engine components, among others.

The effect of surface treatment on the surface texture and contact angle of electrochemically deposited hydroxyapatite coating and on its interaction with bone-forming cells

This work demonstrates the effects of both surface preparation and surface post-treatment by exposure to electron beam on the surface texture, contact angle and the interaction with bone-forming cells of electrochemically deposited hydroxyapatite (HAp) coating. Both the surface texture and the contact angle of the ground titanium substrate changed as a result of either heat treatment following soaking in NaOH solution or soaking in H 2O 2 solution. Consequently, the shape of the current transients during potentiostatic deposition of HAp changed, and the resulting coatings exhibited different surface textures and contact angles. The developed interfacial area ratio Sdr and the core fluid retention index Sci were found more reliable than the mean roughness R a and the root-mean-square roughness Z rms in correlating the adhesion of the coating to the metal substrate and the cellular response with surface texture. The NaOH pretreatment provided the highest surface area and induced the highest cell attachment, even though the H 2O 2 treatment provided the highest hydrophilicity to the metal substrate. Electrodeposition at pH 6 was found preferable compared to electrodeposition at pH 4.2. The ability to modify the cellular response by exposure to unique electron-beam surface treatment was demonstrated. The very high hydrophilicity of the as-deposited HAp coating enhanced its bioactivity.

Texture modification, grain refinement and improved hardness/corrosion balance of a FeAl alloy by pulsed electron beam surface treatment in the “heating mode”

It is demonstrated that significant surface modifications can be generated by low-energy, high-current pulsed electron beam treatments in the “heating mode” (which does not melt the surface). The extremely fast thermomechanical cycles generate grain refinement and texture modification at the surface of a Fe–40 at.% Al alloy. Together with the formation of vacancies, this accounts for a significant increase in the surface microhardness. Nevertheless, because of the absence of craters with the heating mode, the corrosion resistance was unchanged.

Hybrid technology hard coating – Electron beam surface hardening

Hard surface layers often cannot show advantages of their good hardness, strength and wear resistance over relatively soft materials so that an additional thermal treatment of the base materials before or after coating is necessary. Surface treatment technologies with high energy beams {electron beam (EB) or laser beam (LB)} offer a good and modern alternative to the mostly used bulk heat treatment. The energy deposition is precisely focused, so it is possible to exactly limit the heat treatment to highly loaded areas and up to the depth where a transformation (hardening) is necessary. Therefore, the bulk materials are not heated up to critical temperatures. The thermal load of the overall component is minimized and thus distortion can also be avoided. The paper deals with current results of investigations on the combination of PVD hard protective coatings {based on Ti(C)N, TiAlN, Cr x N y and DLC} with electron beam surface hardening. Base materials used for these investigations were different steels (unalloyed steel: C45; low alloyed tool steel: 100Cr6; high alloyed tool steel: X155CrVMo12-1). It is not only the sequence of treatments (beam hardening before or after coating) which has a considerable influence on treatment results, but also the parameters of EB surface treatment (energy density distribution, speed of treatment, vacuum). It will be discussed the relations between treatment conditions, process parameters and surface deformation, layer structure and composition, structure and composition gradients, surface properties, properties gradients and transformation behavior of matrix materials. These modern combined technologies open up new fields of industrial application for tools and components subjected to locally high load.

Simulation of thermophysical and physico-chemical processes occurring at coating formation in electron-beam technologies of surface modification of metallic materials

The paper reviews our theoretical research aimed at studying the processes that accompany electron-beam surface treatment of materials. The major attention is given to the description of nonequilibrium physico-chemical processes occurring in the treatment area. We briefly analyze three types of models corresponding to different technological schemes. The ways of further development of the theoretical approaches used in our research work are discussed.

Microstructure evolution occurring in the modified surface of 316L stainless steel under high current pulsed electron beam treatment

High current pulsed electron beam (HCPEB) surface treatment of 316L stainless steel (SS) was carried out with a wide spectrum of treating parameters. Microstructure changes occurring in the modified surface were characterized with microscopy, X-ray diffractometry and electron backscatter diffractometry (EBSD) techniques. The evolution regularities of surface craters and microstructure refinement, as well as preferred orientation of (1 1 1) crystal planes were discussed on considering the coupled temperature-stress fields formed in surface layers after an absorption of HCPEB energy.

Structure and Properties as a Result of Electron Beam Surface Treatment

A new generation of high frequency 3D deflection technique opens up manifold possibilities for a wider application of electron beam (EB) technologies for surface treatment. A high flexibility of process parameters connected with high productivity is obtained from the simultaneous interaction of the EB in several processing areas or by carrying out several processes simultaneously. The change of material and component‐specific surface properties can be adapted as required. An outstanding improvement of properties can be reached. Typical technological characteristics are explained and the influence of EB parameters on microstructure and properties is discussed. It has been shown that the EB is becoming more and more attractive and important for industrial applications of thermal surface technologies such as hardening, combined thermochemical treatment/hardening, remelting, surface alloying and dispersing

Using a Parametric Design of Two-Step Processes to Predict Quality Characteristics of Heated Treatment by the High-Density Energetic Beam

This study applies the Taguchi method to elucidate the quality characteristic of the melt depth in electron beam surface treatment (EBST) of cast iron. The-nominal and the-better was a measured quality characteristic to evaluate the experimental results by computing the signal-to-noise ratios (SNRs) of the EBST melt depth after surface-hardening tests. It includes two steps to determine the optimum parameters or conditions. The first step is to maximize SNR to minimize the variance, and the second step is to adjust the EBST melt depth to a target value using the sensitivity. Results from the experiment indicate that the optimal process parameters are a substrate matrix of gray cast iron, a travel speed of 39 mm/s, an accelerating voltage of 10 kV, an electrical current of 15 mA, a melt width of 20 mm, an elliptical beam oscillation, and a post-process heat treatment at 150 °C. The best EBST melt depth obtained in the study was 0.747 mm, corresponding to the maximum SNR. The microstructure is composed of fine dendrites and martensite phases. The obtained EBST depth is confirmed by its falling into the predicted 95% confidence interval. The prediction of the optimal setting is close to the actual target value. The reproducibility of the optimal EBST parameters was experimentally established with data from the confirmation run. EBST wear-resistant surface hardening can be performed using Taguchi experiments.

Crease recovery, mechanical and thermal properties of synthetic fabrics treated with electron beam irradiation

The effect of surface treatment of polyester, nylon-6 and cotton/polyester fabrics, with formulations based on polydimethylsiloxane (PDMS) followed by electron beam irradiation, on the crease recovery, mechanical and thermal properties was investigated. The non-reactive siloxane was activated with styrene (S) or methyl methacrylate (MMA) monomers and their corresponding oligomers. The crease recovery properties were determined in terms of the recovery angles in the dry and wet states, while the thermal stability was evaluated by thermogravimetric analysis (TGA) technique. The results showed that the application of MMA/PDMS formulation to the different fabrics improved the crease recovery properties to levels higher than in the case of S/PDMS one. Electron beam surface treatment with S/PDME formulation causes an improvement in tensile mechanical properties, while when MMA/PDMS formulation was applied under the same condition, an opposite trends were observed. The TGA thermograms indicated that electron surface treatment with styrene or MMA formulation has no effect on the thermal stability of polyester, while the treatment with styrene and MMA formulation causes a decrease in the thermal stability of nylon-6 and cotton fabrics within the range 300–450 °C. According to the T max of the rate of reaction gives further supports to this finding.

Electron beam surface treatment. Part I: surface hardening of AISI D3 tool steel

The effects of electron beam surface hardening treatment on the microstructure and hardness of AISI D3 tool steel have been investigated in this paper. The results showed that the microstructure of the hardened layer consisted of martensite, a dispersion of fine carbides and retained austensite while the transition area mainly consisted of tempered sorbite. Also, the microhardness of the hardened layer on the surface increased dramatically compared to that of base material. Finally, the hardening response of AISI D3 tool steel to electron beam surface treatment is closely related to the scanning speed of the electron beam.

Electron beam surface treatment. Part II: microstructure evolution of stainless steel and aluminum alloy during electron beam rapid solidification

Surface rapid solidification microstructures of AISI 321 austenitic stainless steel and 2024 aluminum alloy have been investigated by electron beam remelting process and optical microscopy observation. It is indicated that the morphologies of the melted layer of both stainless steel and aluminum alloy change dramatically compared to the original materials. Also, the microstructures were greatly refined after the electron beam irradiation.

The effect of electrode contamination, cleaning and conditioning on high-energy pulsed-power device performance

High-energy pulsed-power devices routinely use field strengths above those at which broad-area, cathode-initiated, HV vacuum-breakdown occur (>10/sup 7/ to 3/spl times/10/sup 7/ V/m). Examples include magnetically-insulated transmission lines and current convolutes, high-current-density electron and ion diodes, high-power microwave devices and cavities and other structures for electrostatic and RF accelerators. Energy deposited in anode surfaces may exceed anode plasma thermal-desorption creation thresholds on the time scale of the pulse. Stimulated desorption by electron or photon bombardment also can lead to plasma formation on electrode or insulator surfaces. Device performance is limited above these thresholds, particularly in pulse length and energy, by the formation and expansion of neutral and plasma layers formed primarily from electrode contaminants. In-situ conditioning techniques to modify and eliminate the contaminants through multiple HV pulses, low base pressures, RF discharge cleaning, heating, surface coatings and ion- and electron-beam surface treatment allow access to new regimes of performance through control of plasma formation and modification of the plasma properties. Experimental and theoretical progress from a variety of devices and small scale experiments with a variety of treatment methods are reviewed and recommendations given for future work.

Electron beam surface treatment: Industrial application and prospects

Electron beam surface treatment: Industrial application and prospects

Electron beam irradiation effects on fatigue crack growth resistance in an austenitic steel

The effect of electron beam surface treatment (EBST) on fatigue crack growth (FCG) resistance of an austenitic steel has been investigated. The EBST results in significant improvement in the FCG resistance. The beneficial effect is attributed to extensive crack closure as a result of residual stresses originating during EBST. A comparison with the FCG data of the alloy surface treated with other high-energy beam sources such as lasers reveals that EBST could provide similar improvements in the FCG resistance.

Laser beam machining

30CrMnSiA high strength low alloy (HSLA) carbon structural steel is typically applied in equipment manufacturing and aerospace industries. In this work, the effects of continuous electron beam treatment on the surface hardening and microstructure modifications of 30CrMnSiA are investigated experimentally via a multi-purpose electron beam machine Pro-beam system. Micro hardness value in the electron beam treated area shows a double to triple increase, from 208 HV0.2 on the base metal to 520 HV0.2 on the irradiated area, while the surface roughness is relatively unchanged. Surface hardening parameters and mechanisms are clarified by investigation of the microstructural modification and the phase transformation both pre and post irradiation. The base metal is composed of ferrite and troostite. After continuous electron beam irradiation, the micro structure of the electron beam hardened area is composed of acicular lower bainite, feathered upper bainite and part of lath martensite. The optimal input energy density for 30CrMnSiA steel in this study is of 2.5 kJ/cm2 to attain the proper hardened depth and peak hardness without the surface quality deterioration. When the input irradiation energy exceeds 2.5 kJ/cm2 the convective mixing of the melted zone will become dominant. In the area with convective mixing, the cooling rate is relatively lower, thus the micro hardness is lower. The surface quality will deteriorate. Chemical composition and surface roughness pre and post electron beam treatment are also compared. The technology discussed give a picture of the potential of electron beam surface treatment for improving service life and reliability of the 30CrMnSiA steel.