In-situ X-ray investigations of phase formation and diffusion during low energy nitrogen ion implantation into austenitic stainless steel

氮插入过渡金属通常与氮化物的形成有关，例如CrN或Fe3N。然而，fcc相奥氏体不锈钢在固溶体中含有高达30 at的氮。在350至400℃之间，伴随着5 - 15%的各向异性晶格膨胀。同时，观察到氮从表面迅速扩散到体中，遵循d(t) α t1/2定律。许多现有的实验表明，不同群体提出的相形成模型存在分歧。在本项目中，提出了在不同的工艺温度、离子能量和离子电流密度下，对fcc奥氏体不锈钢（及相关材料）进行低能氮离子注入的原位x射线衍射实验，以更好地了解潜在的过程。将现有模型与实验结果进行对比验证，并对其进行修正和完善。除了对辐射增强扩散的见解之外，还将获得关于铁族过渡金属的高氮相形成和稳定性的额外信息。

Nitrogen insertion into transition metals is in general associated with nitride formation, e.g. CrN or Fe3N. However, the fcc phase austenitic stainless steel incorporates nitrogen in solid solution with up to 30 at.% at temperatures between 350 and 400 °C, accompanied by an anisotropic lattice expansion of 5 – 15%. At the same time, a rapid diffusion of nitrogen from the surface into the bulk – following a d(t) α t1/2 law – is observed. Numerous exsitu experiments show diverging results with competing models for the phase formation proposed by different groups. In this project, in-situ X-ray diffraction experiments for low energy nitrogen ion implantation into fcc austenitic stainless steel (and related materials) for varying process temperatures, ion energy and ion current density are proposed to obtain a better understanding of the underlying processes. The existing models will be verified against the experimental results and modified and refined. Beside insights into radiation enhanced diffusion, additional information on the phase formation and stability of high nitrogen phases for transition metals of the iron group will be obtained.