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用光学显微镜、扫描电镜和X射线衍射仪对45、40Cr和20钢深层QPQ处理渗层的显微组织、相组成和氮碳氧元素的浓度分布进行研究。结果表明,深层QPQ处理的渗层组织由氧化膜、疏松层、化合物层、中间层和扩散层组成。氧化膜为Fe3O4;化合物层主要由Fe3N、Fe4N以及少量α相组成;中间层主要由Fe4N和α相组成。氧元素主要存在于氧化膜和疏松层中;氮元素在化合物层中的分布比较平缓;中间层有较高的含氮量和较高的含碳量。通过对疏松层的扫描,观察到疏松层中氮元素明显减少和氧元素明显增加,从而为疏松层是由化合物层中氮原子分子化而形成孔洞的理论提供了直接有力的证据。
The microstructure, phase composition and concentration distribution of nitrogen, carbon and oxygen in QPQ treated 45, 40Cr and 20 steel were investigated by optical microscopy, scanning electron microscopy and X-ray diffraction. The results show that the deep QPQ treated infiltrated tissue consists of oxide film, loose layer, compound layer, intermediate layer and diffusion layer. The oxide film is Fe3O4; the compound layer is mainly composed of Fe3N, Fe4N and a small amount of α phase; the middle layer is mainly composed of Fe4N and α phase. Oxygen is mainly found in the oxide film and loose layer; the distribution of nitrogen element in the compound layer is relatively flat; the middle layer has higher nitrogen content and higher carbon content. Through the scanning of the loose layer, the obvious reduction of nitrogen and the obvious increase of oxygen in the loose layer were observed, which provided the direct and powerful evidence that the loose layer was formed by the molecularization of nitrogen atoms in the compound layer to form the hole.