激光气体氮化工艺可在钛合金表面快速生成氮化层, 提高钛合金表面硬度和耐磨性, 促进钛合金应用。 采用光纤激光气体氮化Ti-6Al-4V合金, 为了明确氮化过程光谱发射区是否形成等离子体, 采用探针法检测了光谱发射区导电性; 为了研究工艺参数对光谱特性、 光谱发射区温度及等离子数量的影响, 采用光谱仪采集了氮化过程发射光谱, 并采用高速摄像拍摄了光谱发射区域照片。 试验表明, 光纤激光气体氮化Ti-6Al-4V合金过程中, 光谱发射区可以导电, 形成了金属蒸汽等离子体, 这与CO₂激光气体氮化钛合金工艺过程中形成的氮等离子体完全不同。 采用光纤激光氮化Ti-6Al-4V钛合金工艺过程中, 工艺参数显著影响金属蒸汽等离子体的数量, 当激光功率较大, 扫描速度较小, 离焦量较小和氮气含量较高时, 光谱发射区可产生金属蒸汽等离子体。 氮化过程发射光谱由连续光谱和线状光谱组成, 连续光谱主要由热辐射产生, 连续光谱强度可以表征光谱发射区温度, 线状光谱主要由等离子区域原子核外电子跃迁产生, 线状光谱强度可以表征等离子体数量。 氮化过程, 随激光功率增大或扫描速度减小, 连续光谱和线状光谱增强, 表明光谱发射区温度升高, 等离子体数量增加; 随离焦量增大, 连续光谱和线状光谱呈先减小后增大之后又减小的复杂变化趋势, 表明光谱辐射区温度先降低后升高之后又降低, 等离子体数量先减少后增加之后又减少; 氮气中加入少量氩气, 可强烈影响氮化过程, 使连续光谱和线状光谱大幅减弱, 随氩气流量进一步增加, 线状光谱和连续光谱继续减弱, 表明氮气中加入少量氩气使光谱发射区温度大幅降低, 等离子体数量大幅减小, 随氩气量进一步增加, 光谱发射区温度继续降低, 等离子体数量继续减少。

Laser gas nitriding technology can quickly generate a nitride layer on the surface of titanium alloy, improve the surface hardness and wear resistance of titanium alloy, and promote the application of titanium alloy. Fiber laser was used to nitride of Ti-6Al-4V alloy, the electrical conductivity of the spectral emission region was measured using the probe method to define whether a plasma was formed in the spectral emission region during the nitriding process. The emission spectra of nitriding process were collected using a spectrograph. The spectral emission region was photographed using a high-speed camera to study the effect of process parameters on spectral characteristcs, the temperature of spectral emission region the quantity of plasma. Experiments show that the spectral emission region can conduct electricity during the process of fiber laser gas nitride of Ti-6Al-4V alloy, which indicates that the metal vapor plasma was formed in the spectral emission region. This was completely different from the nitrogen plasma formed in the process of CO₂ laser gas nitriding of titanium alloy. The number of metal vapor plasma was significantly affected by the process parameters during the process of fiber laser nitriding of Ti-6Al-4V titanium alloy. The metal vapor plasma can be produced in the spectral emission region when the laser power is higher, the scanning speed is lower, the defocusing is low, and the nitrogen content is high. The emission spectrum of the nitriding process is composed of continuous spectrum and liner spectrum. The continuous spectrum is mainly generated by thermal radiation, and the intensity of the continuous spectrum can represent the temperature of the spectrum emission region. The linear spectrum is mainly generated by the extranuclear electron transition of the plasma region, and the intensity of the linear spectrum can represent the quantity of the plasma. In the nitriding process, with the increase of laser power or the decrease of scanning speed, the continuous spectrum and linear spectrum were enhanced, indicating that the temperature of the spectral emission region increases and the number of plasma increases. As the defocus increases, the continuous spectrum and linear spectrum show a complex trend of decreasing first, then increasing and decreasing at last, which indicates that the temperature of the spectral emission region decreases first, then increase and decrease at last, and the number of plasma decreasing first, the increasing and decrease at last. Added a small amount of argon gas, nitriding process can be significantly influenced, the continuous spectra and linear spectra weakened dramatically, with the further increase of argon content, the linear spectrum and continuous spectrum continue to weaken, which indicated that the addition of a small amount of argon to nitrogen reduces the temperature of the spectral emission region and the number of plasma. With the further increase of the amount of argon, the temperature of the spectral emission continues to decrease, and the number of plasma continues to decrease.