Effect of electron beam surface hardening on fatigue crack growth rate in AISI 4340 steel

This paper studies the effect of electron beam (EB) surface hardening on the fatigue crack growth rate in AISI 4340 steel. The heat treatment conditions were varied to consider the influence of microstructure and residual stress. The results show that increasing the EB heat input increases the compressive residual stress in the hardened layer. Thus EB surface-hardening treatment improves the fatigue crack growth resistance. This effect increases with increasing EB heat input but disappears as the ΔK value increases. The fracture mechanism of the hardened layer is intergranular fracture, while that of the base material is transgranular quasi-cleavage.     

Surface treatment of 0.20% C carbon steel by high-current pulsed electron beam

A high-current pulsed electron beam（HCPEB） generated on the system of Nadezhda-2 was applied to improve the microstructure and performance of 0.20% C low carbon steel. Surface layers of the samples bombarded by explosive electron beam at different pulses was observed by using electron microscopy. The physical model of the thermal-stress process and related modification mechanism as a result of HCPEB irradiation was also investigated. After HCPEB post treatments, obvious changes in microstructure and significant hardening occur in the depth of 200-250 μm from the surface after HCPEB irradiation. Rapid heating and subsequent rapid solidification induce heavy plastic deformation, which results in that the laminated structure of pearlite is substituted by dispersive rounded-like cementites in the near-surface. The effect of HCPEB treatment can reach more than 500 m depth from the surface. The original crystalline structure is changed to a different degree that grows with the numbers of bombardment, and in the surface layer amorphous states and nanocrystaline structures consisting of grains of γ-phase and cementite are found. The violent stress induced by HCPEB irradiation is the origin of the nanostructured and amorphous structure formation.     

Surface modification of polyurethane and silicone for therapeutic medical technics by means of electron beam

Surface modification technologies are gaining growing acceptance for treatment of implant materials to enhance biocompatibility. Our examinations focus on polyetherurethane and silicones, two typical flexible implant materials, which we have modified by non-thermal electron beam processing. Advantages of this method are the adjustable degree of modification as well as the simultaneous sterilizing effects.The polymer surfaces were characterized with regard to wetting behavior, surface energy, chemistry and morphology. The cell adhesion was examined too. The results reveal that the electron beam is a useful tool for surface modification of polymers.     

Repair of EDM induced surface cracks by pulsed electron beam irradiation

This study investigates the use of the large-area electron beam irradiation technique to improve the properties of the EDM’d surface of AISI 310 stainless steel so that a tolerable, or even desirable recast layer may be produced. The short cycle-time of the irradiation process combined with the large incident area of 60 mm diameter makes it an attractive surface modification technique for metal moulds and engineering components. This study showed that by varying acceleration voltages and the number of irradiation cycles (shots), that as well as an improvement of surface finish, repair of cracks induced by the EDM process is possible. The mechanism of this repair is also investigated. XRD analysis also shows that crystalline texture can be introduced by the irradiation process with the (1 1 1) planes of the austenite phase orienting parallel to the surface. This has potential advantages for introducing anisotropic layers for enhanced corrosion resistance.     

316L不锈钢强流脉冲电子束表面钛合金化及其耐蚀性

利用强流脉冲电子束对不锈钢表面进行了快速钛合金化。将精细钛粉预涂在基体表面后采用强流脉冲电子束对其进行后处理。在电子束对表面的快速加热熔化、混合及增强扩散效应的作用下,部分钛熔入基体表层形成一层富钛层。由于钛的添加有利于形成α相,合金层由α相和γ相混合组成。在模拟体液中的动态极化测试表明,316L医用不锈钢经强流脉冲电子束表面钛合金化后,其在模拟体液中的耐腐蚀性能获得了显著的提高。     

Evolution of microstructure and non-equilibrium phases in electron beam treated Zr55Cu30Al10Ni5 bulk amorphous alloy

Electron beam (EB) is becoming very popular for the modification of the surfaces as it involves localized melting and fast cooling which helps in achieving the non-equilibrium phases as well as fine microstructure. Surface modification of Zr-based amorphous alloy Zr₅₅Cu₃₀Al₁₀Ni₅ has been carried out by EB melting. Differential scanning calorimetry (DSC) was employed to determine the supercooled liquid region and activation energy of crystallization. The as-cast and modified surfaces of amorphous alloy at different beam conditions were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) techniques. Various phases like NiZr₂, CuZr₂ and Cu₁₀Zr₇ were identified which resulted in the enhancement of hardness of the modified alloy surface.     

Surface roughness of a hot-dipped galvanized sheet steel as a function of deformation mode

A hot-dipped galvanized zinc-coated sheet steel was deformed with three different laboratory test systems: a Marciniak punch system, a flat-die friction test system, and a cupping system. These systems were able to impose various combinations of deformation modes to the sheet. The deformation modes include: (1) strain without die contact, (2) sliding, (3) pressing, and (4) bending. Strain measurements from the electrolitically gridded specimens were made at the same locations as surface profilometry measurements, allowing a direct correspondence of surface roughness with strain. Quantification of the roughening as a function of strain, sliding and bending was determined. The roughening rate depends upon the strain level as well as the strain path. Increased strain without die contact causes an increase in the surface roughness with strain paths close to plane strain exhibiting the highest roughening rate. The deformation modes of sliding, pressing, and bending cause a decrease in the surface roughness (i.e. smoothing) to occur. A first-order model is proposed to account for the surface roughness as a function of these deformation modes.     

HCPEB作用下镀铝CoCrAlY涂层的表面微观结构状态

采用大气等离子喷涂在GH4169镍基高温合金表面沉积CoCrAlY涂层,利用电子束蒸发镀膜技术在涂层表面沉积纳米铝膜,分别对镀铝前后的涂层使用强流脉冲电子束进行辐照处理,对处理前后的涂层表面进行成分及结构分析.XRD结果显示,经过HCPEB轰击之后,涂层表面纳米铝膜重熔,钴类氧化物消失,新增铝相,且随着轰击次数增加,β-CoAl含量增加.结构分析表明,电子束轰击可以使原始涂层表面尖角、孔洞、夹杂等消失,形成非常致密的凸起胞状体纳米超细晶结构,有利于抑制腐蚀性气体的侵入,同时铝含量的增加有利于抗氧化性能的提高.     

Surface finishing of die and tool steels via plasma-based electron beam irradiation

The plasma-based electron beam (PBEB) irradiation with a maximum diameter of 60 mm has been used to smoothen the workpiece surface. After PBEB irradiation, the machined surface roughness is reduced, and its corrosion resistance is improved. However, for die and tool steels, some craters still exist on the surface after PBEB irradiation, which remain a big problem for the roughness improvement and quality control of the machined surfaces. In this study, four types of work materials have been tested during PBEB irradiation. The effects of non-metallic inclusions (MnS and carbide) and impurities on the generation of craters were investigated. In addition, craters formed on the work materials with different nitrogen concentrations have also been observed after PBEB irradiation. Finally, a case study is given, and it is found that PBEM irradiation can achieve good surface finish of die steel materials.     

45钢表面电子束微熔抛光的性能和组织分析

为显著改善45钢表面粗糙度及其综合力学性能. 文中采用电子束微熔抛光技术,对45钢表面进行电子束微熔抛光处理. 研究电子束抛光对表面粗糙度、改性层组织和硬度的影响,探讨了电子束扫描电流、扫描速度对表面粗糙度、改性层组织的影响规律. 结果表明,45钢经表面抛光处理后,表面粗糙度值由2.091 μm降到0.738 μm,降幅为64.7%;其表面改性层可分为抛光层区、热影响区和基体区;抛光层区的显微组织为针状马氏体,硬度为950 ~ 913 HV;热影响区的组织为针状马氏体和铁素体,硬度为855 ~ 280 HV;基体区的组织为珠光体和铁素体,硬度为244 ~ 204 HV. 电子束工艺参数对抛光后的表面粗糙度值影响显著,在满足抛光效果的条件下,改性层的厚度随电子束扫描电流的增加而增大,随扫描速度的增加而减小.     

Structure and hardness of titanium surfaces carburized by pulsed laser melting with graphite addition

Titanium foils coated with graphite films 20 μm thick were irradiated by means of a pulsed Nd-YAG in order to harden this metal by surface melting and alloying. The relationships between irradiation parameters, microstructure and hardness of the synthesized composite coatings were determined. Four relevant parameters were defined as governing the irradiation processes. The parametric working field of the laser source was investigated next to its periphery. The influences of the relevant irradiation parameters on the microstructure and hardness of the melted zone were deduced from the metallographic analyses and Vickers micro-indentation tests of the cross sections of this composite zone. Such a zone was constituted always with hard titanium carbide and ductile metallic titanium, some times with the presence of lubricating graphite inclusions. The main advantage of such a surface treatment of titanium is to synthesize, under clearly defined irradiation conditions, a self-lubricating composite coating that resists abrasive or adhesive wear.     

回火对强流脉冲电子束辐照M50钢重熔层耐蚀性能的影响

利用强流脉冲电子束技术对M50钢进行了辐照处理,并对重熔层在550、600和675 ℃条件下进行了回火处理。采用XRD、SEM和电化学综合测试系统等手段分析了不同处理方式对重熔层组织和耐蚀性能的影响。结果表明,M50钢经过强流脉冲电子束辐照后表层的碳化物溶解,马氏体转变被抑制,耐腐蚀性能上升。经过回火处理后,重熔层内残留奥氏体分解,耐蚀性能逐渐降低。     

45钢电子束相变硬化温度场数值模拟与实验验证

建立了移动电子束高斯热源作用下的三维相变硬化过程中温度场的数学模型,分析过程中考虑了热源分布、热物性参数、热辐射等因素对温度场的影响,得到了电子束扫描相变硬化温度场的分布规律和硬化层的形态,并进行了实验验证;探讨了电子束工艺参数对硬化区深度和宽度的影响。结果表明:移动电子束高斯热源作用下的温度分布等值线呈勺状,表面最高温度滞后于束流中心,且处理后硬化层横截面呈月牙状;在固态相变条件下,硬化层的宽度和深度随着扫描功率的增加呈非线性增加,随着扫描速度的增加呈非线性减小。     

Surface modification of Al-Pb alloy by high current pulsed electron beam

Al-Pb alloy was modified by high current pulsed electron beam and the microstructure, hardness and tribological characteristics were characterized by scanning electron microscopy, electronic microanalysis probe microanalysis, Knoop hardness indentation and pin-on-disc type wear testing machine. The results show that the microstructure and hardness can be greatly improved, and the modification layer consists of a molten zone, an overlapped zone of heat-affected and quasistatic thermal stress-affected zone and a transition zone followed by the substrate. The tribological properties of high current pulsed electron beam irradiated Al-Pb alloy are correspondingly improved largely. Optical observation and scanning electron microscopy analysis reveal that the low wear rate and lowest level in coefficient of friction at high load level for irradiated Al-Pb alloy are due to the formation of a lubricious tribolayer covering the worn surface, which is a mixture of Al2O3, Pb3O4 and silicate. The wear mode varies from oxidative wear at low load to film spalling at high load and, finally, adhesive wear.     

An analysis of grinding power and surface roughness in external cylindrical grinding of hardened SCM440 steel using the response surface method

The aim of this study was to analyze effectively the grinding power spent during the process and the surface roughness of the ground workpiece in the external cylindrical grinding of hardened SCM440 steel using the response surface method. A Hall effect sensor was used for measuring the grinding power of the spindle driving motor. The surface roughness was also measured and evaluated according to the change of the grinding conditions. Response surface models were developed to predict the grinding power and the surface roughness using the experimental results. From adding simply material removal rate to the contour plot of these mathematical models, it was seen that useful grinding conditions for industrial application could be easily determined.     

Microstructure and fatigue crack growth behaviour of electron beam welding in 30CrMnSiNi2A steel

The effects of two post-weld heat treatment processes on the microstructure and fatigue properties of the electron beam welded joints of 30CrMnSiNi2A steel were studied. Electron beam local post-weld heat treatment ( EBLPWHT) , in a vacuum chamber, immediately after welding and a traditional furnace whole post-weld heat treatment (FWPWHT) were accepted. The experimental results show that, after EBLPWHT, the main microstructure of weld is changed from coarse acicular martensite into lath martensite, and base metal is changed from ferrite and perlite into upper bainite and residual austenite, however the microstructures of different zones of joints in FWPWHT conditions are tempered sorbite. The fatigue crack growth rate da/dN of welds and base metal are not obviously changed among EBLPWHT, FWPWHT test and as-welded (AW) test, as the mechanical properties of materials have a certain but not large effect on the da/dN of welded joints. The resistance to near threshold fatigue crack growth data of welded joints can be largely improved by EBLPWHT and it is related to microstructure and crack closure effect.     

钢侧偏束电子束焊接纯铝/Q235异种金属接头试验

采用钢侧偏束电子束焊接方法对铝/钢异种金属接头进行了连接,对接头组织和相组成进行了分析,并对接头抗拉强度进行了了测试.结果表明,钢侧结合良好,焊缝组织均匀,铝侧熔合区存在过渡层,其内有金属间化合物层存在.适当的钢侧偏束量能够提高接头强度,在文中试验范围内,在偏束量为0.5 mm时获得了相对最高的抗拉强度69 MPa.金属间化合层的存在弱化了接头强度,断裂呈脆性特征.     

The model of formation of a non-self-sustained discharge in the plasma in electron beam welding

A model of formation of a non-self-sustained discharge in plasma in electron beam welding is proposed. The electron concentration and electron energy in the plasma above the zone of the effect of the electron beam are calculated by solving the convection–diffusion equations for the density and mean electron energy. Numerical calculations in the construction of the model are carried out using a package of applied software Comsol 4.3, the Plasma Module and the extension DC discharge. The model can be used to calculate the plasma parameters both above the welding zone and directly in the penetration channel.     

脉冲电子束改性TCA钛合金微观组织和性能

采用低能强电流(LEHC)脉冲改性技术处理TC4钛合金表面,利用扫描电子显微(SEM)、场发射扫描电镜(FESEM)、透射电子显微(TEM)和纳米压痕分析(NI)等方法对表面改性层组织进行表征,按照不同低能强电流脉冲改性工艺下改性层的组织特征,结合纳米压痕硬度试验,分析了脉冲电子束改性晶粒的细化机制。结果表明,脉冲电子束改性试样可分为熔化相变层、热影响层和基体三个区域;熔化相变层中的晶粒细化机制是脉冲电子束改性时随着温度的快速升高,表面层发生熔化后的重新结晶以及α相在β相中的析出;晶粒细化是表层纳米压痕硬度提高的主要原因。