An Electron Microscopy Study of Vein-like Grain Boundary Microstructure in Nitrocarburized Low Carbon Steels

作者：Chen, Wanglin; Wu, Cuilan^*; Chen, Jianghua; He, Aigui

来源：Journal of Materials Science & Technology, 2013, 29(7): 669-672.

DOI：10.1016/j.jmst.2013.03.027

• Nitrocarburizing
• Grain boundary
• gamma '-Fe-4(C,N)
• epsilon-Nitrocarbide

The coarsened grain boundaries (GBs) with vein-like morphology frequently appear in the nitrogen diffusion layer of nitrocarburized carbon steels. The electron probe X-ray microanalysis shows that such vein-like GBs are rich in nitrogen and carbon atoms. Transmission electron microscopy and scanning electron microscopy further reveal that the coarsened GBs consist of gamma'-nitrocarbide (Fe-4(C,N)) and epsilon-nitrocarbide lamellas that are formed during nitrocarburizing due to high nitrogen concentration at GBs. It is shown that many of {111}< 112 > micro twins exist in the gamma'-phase lamellas and thin epsilon-phase slices prefer to nucleate at their twin boundaries with the orientation relationship of {0001}(epsilon)//{111}(gamma'). Upon growing large gamma'-lamellas may become faceted and thin e-lamellas may grow thicker and become the main portions in the vein-like GBs. The microstructure evolution occurring in the vein-like GBs can be depicted as: alpha + [N]/[C] -> gamma' + [C,N] -> epsilon-nitrocarbides.

• 出版日期2013-7
• 单位湖南大学