Rapid nitriding mechanism of titanium alloy by gas blow induction heating
Rapid nitriding mechanism of titanium alloy by gas blow induction heating
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DOI：
10.1016/j.surfcoat.2020.126160
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发表时间：
2020-10
影响因子：
5.4
通讯作者：
Shogo Takesue;S. Kikuchi;Y. Misaka;T. Morita;J. Komotori
中科院分区：
文献类型：
--
作者：
Shogo Takesue;S. Kikuchi;Y. Misaka;T. Morita;J. Komotori
对钛合金吹气感应加热（GBIH）过程中产生的表面改性层进行了表征，以阐明其快速渗氮机理。采用X射线衍射仪、显微维氏硬度计、扫描电子显微镜和X射线光电子能谱仪对GBIH渗氮试样的表面组织进行了分析。结果表明，在Ti-6Al-4V合金表面上，仅用几分钟的时间就能形成与普通气体渗氮几小时所形成的渗氮层相似的渗氮层。GBIH渗氮过程中，材料内部温度高于表面温度。然而，氮化层的厚度超过了基于在该高内部温度下的扩散系数的估计值。这种特别厚的氮化层可能归因于通过施加高频电流在金属中产生的涡电流。GBIH氮化可使Ti-6Al-4V合金表面的钝化膜消失，这是由于钝化膜中的氧原子向基体中扩散所致。因此，数据表明，GBIH渗氮能够基于涡流效应和钝化膜的消失在短时间内对Ti-6Al-4V合金进行改性。
This work characterized the surface-modified layers generated on a titanium alloy during gas blow induction heating (GBIH), so as to elucidate the rapid nitriding mechanism. The surface microstructures of GBIH nitrided specimens were analyzed by X-ray diffraction, micro-Vickers hardness testing, scanning electron microscopy and X-ray photoelectron spectroscopy. The data indicate that applying this process for only several minutes can forms nitrided layers on Ti-6Al-4V alloy surfaces, the characteristics of which are similar to those of layers produced by ordinary gas nitriding for several hours. The temperature inside the material was determined to be higher than that on the surface during GBIH nitriding. However, the thickness of the nitrided layer exceeded the estimated value based on the diffusion coefficient at this high internal temperature. This especially thick nitrided layer can possibly be attributed to eddy currents generated in the metal by the application of a high-frequency current. Passivation films on the surface of the Ti-6Al-4V alloy were found to be removed during GBIH nitriding, which is ascribed to the diffusion of oxygen atoms in the passivation film into the substrate. Thus, the data show that GBIH nitriding is able to modify a Ti-6Al-4V alloy within a short period of time based on the effect of an eddy current and the disappearance of the passivation film.