【作者】 黄玉堂；

【导师】 周上祺；

【作者基本信息】 重庆大学 ， 材料学， 2007， 硕士

【摘要】 工程上绝大多数零件的失效都是从表面开始的,开发新的表面强化技术对于提高机械零件的使用寿命具有重要的意义。离子渗氮技术由于渗氮层性能好、生产周期短、工件变形小等优点,在工业生产上得到广泛的应用。研究和开发以离子渗氮为基础的复合工艺,节能降耗、减少污染,是当前该领域的一个热点。本文从减少环境污染出发,用氮气取代常用的氨气,以氮气-甲烷混合气体作为气源,探讨在工业生产中广泛应用的离子软氮化工艺。采用金相显微镜、扫描电镜、X射线衍射仪、显微硬度计、MRH-3型磨损试验机、电化学性能分析测试仪等实验手段,分析测试了40Cr钢经氮气-甲烷离子氮碳共渗工艺处理后的成分、组织、结构、性能,并与常规离子渗氮进行了比较。对氮气-甲烷离子氮碳共渗的机理进行了初步分析讨论。结果表明:①4 0Cr钢经氮气-甲烷离子氮碳共渗后,显微组织与常规离子渗氮相似,由化合物层、扩散层和基体三部分组成。②在同样的氮气-甲烷流量比下,试样表层的硬度随着试验电压的降低而递减;在同一试验电压下,随着甲烷流量的增大,试样表层的硬度显著增加,所获得的渗层也较深。③经氮气-甲烷离子氮碳共渗处理后,40Cr钢共渗层的氮化物以ε-Fe3N为主,随着工艺参数的变化,还可能出现Fe2N、Fe4N和Fe3C相。无论耐磨性还是耐蚀性,都以ε- Fe3N相性能最佳。④甲烷离解产生的活性碳原子,为渗碳提供了物质前提,加速了表面氮化物的形核;离解产生的H·充当“炮弹”作用,不仅去除钝化膜且活化工件表面,更重要的是碰撞时将自身的大部分能量传递给氮分子,使氮分子离解成活性氮原子,大大降低了活性氮原子产生的电压门槛值。⑤氮气-甲烷的离子软氮化工艺是可行的,且工作环境好,污染小。更多还原

【Abstract】 In industry, most of failures of machine parts often begin from their surfaces, so it is important to explore new surface-strengthening technologies in order to improve their durability. Ion nitriding is well–known surface modification technique extensively used in the modern industries to enhance the mechanical properties of nitrogen layer, shorten the period of production, reduce the formation of workpiece etc. Recently, research and development of combined processes on the basis of ion nitriding, economized energy sources and decreased environmental contamination are focus in this area. The paper discusses 40Cr Steel which was treated by compound treatment method of N, C co-diffusing with N2 and CH4. its idea is what decreases environmental contamination and substitutes NH3 for N2.The constitution of phases, the microstructure and the properties of the modified layers were analyzed using Microscopy, X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Microhardness Apparatus and MRH-3 Wearing Machine, and were compared with those treated by conventional nitriding. The mechanism of the ion N-C component permeation is discussed in the end of this article. The results in this paper are following:①the composite layer of 40Cr Steel which is treated by compound treatment method of N, C co-diffusing, can divide into three layers. The surface layer is chiefly N,C compound. The second layer is diffused layer. The third layer is basic structure. When voltage of test was 600V, depth of the compound layer was deepest.②when proportion of N2 to CH4 is constant, microhardness of sample surface enhance as voltage of test reduce; when voltage of test is constant, as CH4 increases, the max hardness heightens and composite layer obtained is deeper.③Phase composition of the composite layer main containεphase(N,C compound); when ion nitrocarburizing process is changed, composite layer may be include Fe2N, Fe4N and Fe3C phase.its wear resistance and corrosion resistant property is the best with singleεphase.④t he CH4 plays important roles in ion-nitrocarburizing. It decomposes carbon which provide physical premise of carburizing and accelerate nucleation of nitride. It decomposes H·which serve as shot to clean out surface passivation and improve surface activation, H·has more important which transfer energy itself to N2 when impact each other. So voltage threshold of producing active nitrogen atoms is reduced more.⑤I on-nitrocarburizing Technique with N2 and CH4 is available and friendly to environment.更多还原