激光和等离子体混合法氮化铁表面

采用激光和氮等离子体混合方法在大气气氛下对铁样品表面进行处理，获得了铁氮化合物表层。利用X射线衍射仪（XRD）对氮化处理样品测试，得到样品的相结构。分别使用混合方法与普通激光氮化方法，在相同条件下对样品表面进行氮化处理，结果表明通过混合方法提高了氮化物含量，并有效地抑制了氧化发生。利用扫描电镜（SEM）测量氮化后样品得出氮的最大质量分数可达34．44％，有效氮化层深度可达11．21μm。讨论激光功率密度、氮等离子体流量、扫描速度等参数对混合法氮化效果的影响。在实验条件下，激光功率密度和扫描速度分别与氮化物衍射峰相对强度成线性递增关系和二次方递减关系。而随着氮等离子体流量的增加，氮化物含量增加；但是当氮等离子体流量大于0．9m^3／h后，氮化所需活化氮达到饱和，氮化物含量不再增加。另外，氮化后样品的硬度得到了增强。

Nitriding Surface of Iron by the Mixing Method with Laser and Plasma Beams

Iron nitride was obtained by the mixing technology with laser and plasma beams nitriding coaxially on the surface of iron in atmosphere. X-ray diffraction (XRD) measurements reveal formation of iron nitride in the as-treated sample. The more iron nitrides can be obtained by the mixing method than that by the common laser nitriding method. And the oxidation was restrained by the mixing method, too. The max weight% of N in treated sample is 34.44% and the effective nitriding depth of 11.21 μm is obtained by scanning electron microscopy (SEM) method. The relationship of nitriding results with different laser energy densities, different nitrogen plasma fluxes and different scanning speed was discussed, respectively. The XRD relative peak value of iron nitride linearly increases with laser energy density. The quantities of iron nitrides increase with the increase of nitrogen plasma fluxes. However, when nitrogen plasma flux is more than 0.9 m3/h, the quantities of iron nitrides do not increase anymore. The iron nitride diffraction peak value quadratically decreases with scanning speed. Moreover, the hardness of nitriding sample is enhanced.