Nanostructures in austenitic steel after EDM and pulsed electron beam irradiation
Nanostructures in austenitic steel after EDM and pulsed electron beam irradiation
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DOI：
10.1016/j.surfcoat.2014.10.045
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发表时间：
2014-11
影响因子：
5.4
通讯作者：
J. Murray;J. Walker;A. Clare
中科院分区：
文献类型：
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作者：
J. Murray;J. Walker;A. Clare
由EDM产生的重铸层通常表现出高水平的残余应力、不可接受的裂纹密度和高表面粗糙度;所有这些都将导致表面完整性降低和疲劳寿命降低。以前的研究表明，表面的电火花加工的组件可以成功地提高通过使用大面积脉冲电子束表面改性，这是通过一个快速重熔过程，结果在一个净平滑的工件表面。它也已被证明，由EDM创建的裂纹被修复的区域内熔化的EB照射，因此，该过程被提出来减少EDM对疲劳寿命和有害的表面性能的影响。在这项工作中，复杂的多层膜的近表面询问TEM和XRD。首次对辐照过程中产生的整个重熔层进行了FIB-TEM研究。这些层的表征对于预测材料在应用中的性能是必要的。脉冲EB辐射被证明是能够创建几个不同的纳米结构，其中包括不同的晶粒尺寸和晶粒取向的表面层。重熔层中以奥氏体为主，最上表面产生的晶粒尺寸小至5 nm。也存在于该层中的针状相被认为是可熔的。
The resulting recast layer from EDM often exhibits high levels of residual stress, unacceptable crack density and high surface roughness; all of which will contribute to diminished surface integrity and reduced fatigue life. Previous studies have shown that the surface of EDM'd components can be successfully enhanced through the use of large-area pulsed electron beam surface modification, which, through a rapid remelting process, results in a net smoothing of the workpiece surface. It has also been shown that cracks created by EDM are repaired within the region molten by EB irradiation, and therefore the process is proposed to reduce the impact of EDM on fatigue life and deleterious surface properties. In this work the complex multilayers of the near surface are interrogated by TEM and XRD. A FIB-TEM study of the entire remelted layer produced by the irradiation process has been performed for the first time. The characterisation of these layers is necessary for predicting the performance of the material in application. Pulsed EB irradiation was shown to be capable of creating several distinct surface layers of nanostructures which consist of varying grain sizes and grain orientations. Austenite was revealed as the dominant phase in the remelted layer, with a grain size as small as 5 nm produced at the very top surface. A needle-like phase also present in the layer is thought to be cementite.