Abstract This work presents a detailed microstructure-property correlation of high power diode laser nitrided titanium based on its dendrite and martensite microstructures, structural phase and microhardness. For the laser nitrided titanium, cooling rate was estimated for the first time using empirical power law relationship by considering the martensite width and dendrite arm spacings and the results were validated by analytical thermal model. A processing window was formulated for laser gas nitriding of titanium by relating the experimental parameters such as laser processing parameters, nitrogen gas pressure and titanium nitride phases. The novelty of this work is demonstration of laser nitriding of titanium in laminar flow nitrogen gas environment using a simple acrylic container setup that avoids design and fabrication of a complex gas nozzle delivery system. In this setup, a thin transparent acrylic sheet was used as optical window instead of expensive quartz glass, to transmit high power diode laser beam at 980 nm wavelength to irradiate the substrate work piece in a closed container. This simple laser nitriding technique has created characteristic golden colored TiN surface with high surface hardness. Dendrite and martensite microstructures of the laser nitrided titanium were analyzed by optical and FESEM microscopy. EDAX analysis revealed the presence of nitrogen in laser nitrided titanium and X-ray diffraction confirmed the TiN phases. The microhardness of laser nitrided titanium is six times higher than its substrate.

中文翻译：

---

在氮气填充的简单亚克力盒式容器中对钛进行高功率二极管激光氮化：显微组织、相形成、硬度、枝晶和马氏体凝固分析

摘要 这项工作根据高功率二极管激光氮化钛的枝晶和马氏体显微组织、组织相和显微硬度，详细介绍了钛的显微组织-性能相关性。对于激光氮化钛，通过考虑马氏体宽度和枝晶臂间距，首次使用经验幂律关系估算冷却速率，并通过分析热模型验证结果。通过关联激光加工参数、氮气压力和氮化钛相等实验参数，制定了钛激光气体氮化的加工窗口。这项工作的新颖之处在于使用简单的丙烯酸容器设置在层流氮气环境中演示钛的激光氮化，避免了复杂的气体喷嘴输送系统的设计和制造。在此设置中，使用薄透明亚克力板代替昂贵的石英玻璃作为光学窗口，以传输 980 nm 波长的高功率二极管激光束来照射密闭容器中的基板工件。这种简单的激光渗氮技术创造了具有高表面硬度的特征性金色 TiN 表面。通过光学和 FESEM 显微镜分析激光氮化钛的枝晶和马氏体微观结构。EDAX 分析显示激光氮化钛中存在氮，X 射线衍射证实了 TiN 相。