【作者】 魏宏璞；

【导师】 石世宏；

【作者基本信息】 苏州大学 ， 机械制造， 2010， 硕士

【摘要】 阀门是核电站正常安全运行必不可少的重要控制部件,核电阀门密封面堆焊层的质量是影响阀门性能的重要因素之一。目前核阀密封面堆焊材料一般均为含钴合金。然而,钴基合金不仅价格昂贵,特别是在核环境下工作时,钴基合金磨损和腐蚀碎片中的Co-59受激发将形成Co-60同位素,这会延长核辐射的半衰期,因此今后第三代核级阀门的密封面都要求采用无钴材料。本文设计了一种可应用于核电阀门密封面堆焊层的新型无钴铁基合金。以铁为主体,添加C、Ni、Cr、B、Si、W、V、Mo、Mn等合金元素,制备成新的合金粉末,并将其命名为CL-1。堆焊层性能与质量不仅取决于堆焊材料,而且在很大程度上还取决于堆焊方法与工艺。本文采用光内送粉激光熔覆新工艺在不锈钢基体上熔覆CL-1涂层。对环形中空光和常用的实心高斯光比较发现,中空光在透光率、光束能量分布以及熔池对流形态方面具有诸多优势,获得的熔层质量更高、组织性能更好。显微硬度测试发现激光熔覆层显微硬度是基体的1.6-1.8倍;通过SEM结构组织分析表明:熔覆层上呈现组织依次为窄胞状晶区、粗大树枝晶区、细小树枝晶和等轴晶区这样一个变化趋势;通过涂层XRD物相分析发现主要为Fe63Mo37,Fe2Si,Fe0.4Mn3.6C,Fe2SiV,Ni2Si以及Fe7.79Mn2.20Si6等相。同时,熔覆层中含有许多细小的各种碳化物,如Fe3C、Fe5C2、Mn5C2等,这些碳化物本身具有较高的硬度。由于它们的存在,会在熔覆层中生成大量的位错和层错等结构,使得硬度增加,同时它们本身也会起到弥散强化作用。XRD分析还发现通过基体元素的扩散,合金元素渗入会引起固溶强化和第二相强化;EDS能谱分析发现在激光熔覆的过程中发生了元素扩散,熔覆层与基体实现了良好的冶金结合。通过热腐蚀试验发现,CL-1无钴铁基合金激光涂层的耐热腐蚀性能优于Noremo02铁基合金熔覆层,接近Stellite6钴基合金熔覆层的耐热腐蚀性能。对激光熔覆层耐高温摩擦磨损试验结果进行比较,发现CL-1无钴铁基合金粉末在高温性能方面介于两者之间,稍优于Noremo02,接近Stellite6钴基合金。综合各项测试结果可知,CL-1无钴铁基合金粉末各项性能都接近Stellite6钴基合金粉末,在一定程度上,可以取代Stellite6钴基合金粉末成为核电阀门密封面堆焊层材料。更多还原

【Abstract】 Nuclear valves are necessary and important control components for normal safe operation of nuclear power station. The quality of nuclear power valve sealing surface surfacing is an important factor of safety security of nuclear power. The current nuclear valve sealing surface surfacing material is generally cobalt alloy. However, Co-based alloy is not only expensive, but also particularly when working in a nuclear environment, wear and corrosion debris of cobalt-based alloy is stimulated from Co-59 to isotope Co-60 which have long half-life of nuclear radiation. So the nuclear valve sealing surfaces of the third-generation need Co-free materials.A new Co-free Fe-based alloy powder is designed to be applied in the valve sealing surface overlaying, in which the Iron as the main body, C, Ni, Cr, B, Si, W, V, Mo, Mn and other alloy elements are added. And the new alloy powder is named CL-1.Surfacing layer not only depends on performance and quality surfacing materials, but also to a large extent also depends on the welding methods and process. In this paper, the internal laser feeding technology is applied and the powder is cladded on stainless steel substrate. Circular hollow light compared with the commonly used solid Gaussian shows that the beam energy distribution of hollow light and weld pool convection patterns has many advantages, such as the higher quality melting layer, better organizational performance.Micro-hardness test shows that hardness of laser cladding layer is 1.6-1.8 times the matrix; through the structural organization of SEM analysis shows that: cladding layer followed by an organization presents a narrow cellular crystal, coarse dendrite area, small branches crystal and equiaxed grain zone. Such a trend; by XRD phase analysis of coating was found mainly Fe63Mo37, Fe2Si, Fe0.4Mn3.6C, Fe2SiV, Ni2Si and Fe7.79Mn2.20Si6 other phase. Meanwhile, the cladding layer contains many of the small variety of carbides, such as Fe3C, Fe5C2, Mn5C2 Such carbide itself has a higher hardness.Same time, because their existence, generation a large number of dislocations and stacking faults and other structures in the cladding layer, while they themselves will play a dispersion strengthening effect.XRD analysis also found that the diffusion through the matrix elements, alloying elements may cause infiltration of solid solution strengthening and the second phase strengthening; EDS spectrum analysis found that the process of laser cladding elements occurred in the proliferation of cladding layer and the substrate to achieve a good metallurgical bonding. Found through the hot corrosion test, CL-1 Fe-based Co-free alloy powder laser cladding of corrosion resistant than Noremo02 Fe-based alloy cladding layer, close to Stellite6 Co-based heat-resistant alloy cladding corrosion.High temperature friction and wear test results show that CL-1 Co-free Fe-based alloy powder at high temperature performance in between, better than Noremo02, close to Stellite6 Co-based alloy.Synthesis of the test results suggest that the performance of CL-1 Co-free Fe-based alloy powder is close to Stellite6 Co-based alloy powder. To a certain extent, it can replace Stellite6 Co-based alloy powder into nuclear power valve sealing surface weld overlay material.更多还原