【作者】 包娟娟；

【导师】 冷永祥；

【作者基本信息】 西南交通大学 ， 材料科学与工程， 2010， 硕士

【摘要】 金属铀是重要的核材料,但其在使用环境中易被腐蚀,因而铀表面防腐蚀技术长期以来都是核材料领域的重要研究课题。离子注入由于其改性层与基体逐渐过渡,不会剥落而在材料防护上具有独特的技术优势。为了研究铀氮化后的耐磨抗蚀性,本文选用工业纯铁作为模型材料,采用高频低压等离子体注入(HLPⅢ)及氮化技术在工业纯铁(模拟材料)上进行氮离子注入及氮化处理,研究射频功率及氧分压对氮化后样品表面结构、成分及性能的影响。在此基础上,将高频低压等离子体注入(HLPⅢ)及氮化技术应用到异型零件(如球)上,研究脉冲频率对其表面改性层均匀性及性能的影响。利用X射线衍射(XRD)、X射线光电子能谱(XPS)、扫描电子显微镜(SEM)对改性层的相结构、成分及断面组织进行分析；利用HXD-1000 knoop显微硬度仪和CSEM销盘式摩擦磨损实验机评价改性前后工业纯铁的硬度及耐磨性等机械性能；利用电化学腐蚀实验评价了改性后工业纯铁的耐腐蚀性。依据电化学腐蚀中的极化曲线,用电量法计算改性层的孔隙率。研究结果表明,采用高频低压等离子体浸没离子注入(HLPⅢ)及氮化技术能在纯铁表面制备出结构致密、耐磨性和耐腐蚀性能优良的氮化物改性层。射频功率影响铁氮化合物的形成,并随着射频功率的增加,氮化层厚度增加,由1μm左右增至3μm左右,纯铁的表面硬度、耐磨性和耐腐蚀性提高。射频功率为600W和800W时,纯铁表面的硬度相差不大,但800W时纯铁的耐磨性和耐腐蚀性优于600W。真空室中残余的氧对氮化物的形成有很大的影响,当氧分压小于6.5×10-3Pa时,残余氧的存在不影响氮化层的结构和性能,表面改性层主要由Fe2N和Fe3N相组成,样品具有高的硬度、耐磨性和耐腐蚀性；但是,随着氧分压的增大(大于9.4×10-3Pa),样品表面的相结构由Fe2N和Fe3N的混合相向Fe3N和Fe3O4的混合相转变,硬度和耐磨性降低,耐腐蚀性下降。球经高频低压等离子体浸没离子注入及氮化处理后,样品表面的硬度、耐磨性和耐腐蚀性显著提高,具有较好的均匀性。脉冲频率对球表面均匀性、相结构、机械性能和耐腐蚀性能没有明显影响。更多还原

【Abstract】 Uranium is a kind of important nuclear material, whose corrosion resistance is weak, and thus the protection of uranium against corrosion is an important subject in nuclear technology, especially for long term storage of non-irradiated components. Plasma immersion ion implantation is a well-known method for protection of metals against wear, fatigue and corrosion. So high frequency and low voltage plasma immersion ion implantation (HLPIII) nitriding technology at different RF power and O2 partial pressure has been applied to improve the industrial pure iron (simulation material of uranium) properties in this paper. Then the nitriding layer prepared by high frequency and low voltage plasma immersion ion implantation (HLPIII) nitriding technology with different pulse frequency on the ball was synthesized.After the HLPIII treatment, mechanical property and corrosion resistance of samples were evaluated and compared with the virgin Fe. The microstructure of the nitriding layer was characterized by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy(XPS). The thickness of nitriding layer was evaluated by scanning electron microscopy (SEM). The microhardness was analyzed by HXD1000 microhardness meter, the wear resistance was analyzed by CSEM pin-on-disk wear testing machine, and the corrosion resistance was measured in a 0.9% NaCl solution at room temperature. The porosity ratio was calculated using coulometric method based on the polarization curves.The result indicated that the nitriding layer was synthesized on industrial pure iron using high frequency and low voltage plasma immersion ion implantation (HLPIII) and nitriding technology. The RF power influenced the phase structure and the depth of the nitriding layer of industry pure iron. With the RF power increased, the depth of the nitriding layers was increased to 3μm from 1μm, the hardness, wear resistance and corrosion resistance were raised. The O2 partial pressure influenced the formation of iron nitride. When the O2 partial pressure was less than 6.5×10-3Pa, the existence of residual oxygen didn’t influence the structure and properties of the nitriding layer. And the Fe2N and Fe3N coexisted in the nitriding layer, the nitriding layer had higher hardness, wear resistance and corrosion resistance. However, with the O2 partial pressure increased (>9.4×10-3Pa), the phase structure Fe3N and Fe3O4 was formed in nitriding layer, and the hardness, wear resistance and corrosion resistance decreased with the increasing of O2 partial pressure. The hardness, wear resistance and corrosion resistance of the ball were significantly increased after the treatment of HLPIII, and had better uniformity. Pulse frequency had no significant imfluence on hardness, wear resistance and corrosion resistance of the ball treated by HLPIII.更多还原