Surface modification of aluminum using ion nitriding and fluidized bed
Surface modification of aluminum using ion nitriding and fluidized bed
复制标题
采用离子渗氮和流化床对铝进行表面改性
DOI：
10.1016/s0257-8972(01)01151-3
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发表时间：
2001
影响因子：
5.4
通讯作者：
Toshiyuki Murayama
中科院分区：
文献类型：
--
作者：
M. Okumiya;Y. Tsunekawa;Toshiyuki Murayama
近年来，铝的应用已扩展到机械零件的轻量化领域。然而，Al的硬度低于目前主要用于这些机械零件的钢的硬度。因此，为了将其用于滑动部件，有必要对铝进行表面改性。通过在氮等离子体中加热，离子氮化在钢表面形成氮化层。离子氮化作为一种加工工具被广泛应用于提高碳钢或合金钢等机械零件的疲劳和耐磨性。然而，铝表面存在一层致密的氧化膜，这阻碍了离子渗氮形成氮化层。因此，离子氮化对铝合金的应用是困难的。在本研究中，在填充氧化铝(Al2O3)/铝镁（Al - mg）合金粉末的流化床中，首先在铝表面形成氮化铝（AlN）层，从而实现离子氮化。此外，还考察了工艺参数对氮化铝膜厚度和硬度的影响。氮化后，用XRD对改性层的成分进行鉴定，用光学显微镜观察其结构和厚度，用显微维氏硬度计测定其硬度。所有条件下的处理时间为18.0 ks。比较了三种渗氮方式下AlN改性层的厚度：纯流化床渗氮；流化床后气体氮化；以及流化床后离子氮化。氮化后，衬底上有两层，一层是由AlN组成的改性层，另一层是由al2o3和AlN组成的沉积层。随着流化床停留时间的增加，改性层和沉积层的厚度增加。对于组合工艺，改性层的厚度小于单独流化床氮化处理的厚度。在靠近沉积层的区域，改性层的AlN浓度和硬度较高。沉积层的厚度仅随流化床时间的增加而增加。当使用气体或离子氮化时，可能只有改性层的厚度增加。此外，离子渗氮形成的改性层硬度高于气体渗氮形成的改性层。离子渗氮改性层厚度减小，流化床渗氮改性层厚度减小。
Recently, applications of aluminum (Al) use have extended into the area of the lightening of machine parts. However, the hardness of Al is lower than that of the steel mainly used for these machine parts at present. Therefore, it is necessary to carry out surface modifications of Al in order to use it in sliding parts. By heating in a nitrogen plasma, ion nitriding forms a nitride layer on the steel surface. Ion nitriding is widely used as a processing tool to increase the fatigue and wear resistance of machine parts of carbon or alloy steels, etc. However, a dense oxide film exists on the surface of Al, which prevents the formation of a nitride layer by ion nitriding. Therefore, it is difficult to apply ion nitriding to Al alloys. In this study, an aluminum nitride (AlN) layer was first formed on the surface of Al in a fluidized bed filled with alumina (Al2O3)/aluminum magnesium (Al–Mg) alloy powder, and ion nitriding was thus enabled. In addition, the influence of process parameters on the film thickness and hardness of the AlN layer was examined. After nitriding, constituents of the modified layer were identified by XRD, the structure and thickness were observed by optical microscopy, and the hardness was measured by a micro Vickers hardness tester. The processing time for all conditions was 18.0 ks. The thickness of the AlN modified layer was compared for three nitriding methods: fluidized bed only; gas nitriding after fluidized bed; and ion nitriding after fluidized bed. After nitriding, there are two layers on the substrate, one is the modified layer composed of AlN, and the other is a deposited layer composed of Al2O3and AlN. With increasing time in the fluidized bed, the thickness of the modified and deposited layers increases. For the combined processes, the thickness of the modified layer is less than that carried out by fluidized-bed nitriding alone. In regions close to the deposited layer, AlN concentration and hardness in the modified layer are high. The thickness of the deposited layer increases only with increasing time in the fluidized bed. It is possible that only the thickness of the modified layer increases when gas or ion nitriding is used. In addition, the hardness of the modified layer formed by ion nitriding is higher than that formed by gas nitriding. The thickness of the modified layer formed by ion nitriding decreases, along with that formed by fluidized-bed nitriding.