高效打蛋破壳刀片渗硼与渗钒处理后微观组织与性能变化. (Chinese)

Changes in the microstructure and properties of the egg-break blade after boronisation and vanadizing. (English)

Egg-break blade is a key component in a high-efficiency egg separator. Two failures of egg-break blade usually occurred in the turning of cutting edge and blade wear. The strategy to prolong the lifetime of egg-break blade is to increase the hardness without too much sacrifice of toughness. In this study, the boriding and thermal diffused vanadizing were applied to a blade stainless steel of 2Cr13, thereby to achieve an excellent wear resistance. The microstructure, mechanical properties, and wear behaviors of the layers were investigated after the treatment. A scanning electric microscopy (SEM) equipped with energy dispersive X-ray spectroscopy (EDS) was employed to observe the thickness, microstructure, and chemical composition from the cross section of the layers. The crystal structure was detected by X-ray diffraction (XRD) from the top surface. The results suggested that the boride and vanadizing layers were successfully fabricated on the surface of 2Cr13 stainless steel, showing excellent adhesion with the substrate. The thicknesses of boride and vanadizing layer were 15 μm and 5μm, respectively. The much thinner vanadizing layer was related to the larger diameter of atom, resulting in a sluggish diffusion. It can also be confirmed by the content of B and V in the corresponding layer. There was nearly 30% B in the boride layer, while, only 12.3% V content in the vanadizing layer. According to XRD patterns, the boride layer consisted of FeB, Fe2B, Fe3B, while, the vanadizing layer mainly consisted of VCx carbides. The borides and carbides formed via the diffusion and reaction with the interior elements of the substrate. The micro-hardness of coating and substrate can be measured from the surface with a load of 0.49 N. The hardness of boride layer and vanadizing layer were 1 554 and 1 037 HV, respectively, which were three and 2-3 times higher than that of the treated stainless steel. The high hardness can be attributed to the formation of borides and carbides after the treatment. The relatively low hardness in the vanadizing layer can be related to the low content of VCx. Nano-indentation test was carried out to further determine the mechanical properties, including the nano-hardness, elastic recovery ability (We) and energy dissipation coefficient (Kd). The nano-hardness of diffusion layers was like the results of micro-hardness. The boride layer presented a higher elastic recovery ability than the vanadizing layer, whereas, the vanadizing layer showed the better performance of plastic deformation. In friction test, the results demonstrated that the coefficient of friction (COF) in the vanadizing layer was relatively lower of 0.5, compared with the boride layer, where the COF was about 0.68. Nevertheless, the boride layer presented a lower wear rate under non-impact load, indicating better wear resistance due to its higher hardness. Taking the thickness and mechanical properties into account, the vanadizing layer with better performance of plastic deformation can be a potential application to protect the cutting edge from turning, whereas, the boride layer with higher hardness can be a candidate to improve the wear resistance of blade body served under a stable load. [ABSTRACT FROM AUTHOR]

刀片卷刃和刀片磨损是破壳刀片的两大失效形式，这将决定着破壳器的使用效率。其中延长破壳刀使用寿命的 有效解决方式便是提高材料硬度并保持其韧性。为此，该研究采用渗硼和 TD 渗钒 2 种工艺对 2Cr13 不锈钢破壳刀进行 处理，以提高刀片的耐磨性，并对处理后的组织结构、机械性能以及摩擦性能进行研究。采用扫描电镜（Scanning Electron Microscope, SEM）和 X 射线能谱分析（Energy Dispersive Spectrum, EDS）从截面到涂层的厚度、组织和化学成分进行分 析，利用 X 射线衍射仪（X-ray Diffraction, XRD）从表面对材料的晶体结构进行分析。结果表明，在 2Cr13 不锈钢破壳 刀表面成功实现渗 B 与渗 V 处理，并有较好的附着性。处理后涂层厚度分别为 14.8 与 5.2 μm，渗钒涂层较薄是由于大原 子半径使得扩散迟缓，其中渗 B 涂层原子百分含量为 30%，而渗 V 涂层含量为 12.3%。根据 XRD，渗 B 涂层主要由 FeB、Fe2B、Fe3B 组成，而渗 V 层主要由 VCx 组成，这些硼化物和碳化物是通过扩散与内部原子反应生成的。采用 0.49 N 载 荷对涂层和基体硬度进行测量发现渗 B 层和渗 V 层的硬度分别为 1 554 和 1 037 HV，因此硼化物和碳化物的高硬度使得 硬度相对未处理前提升了 2～3 倍，其中 VCx 导致渗 V 层硬度相对较低。为进一步探究机械性能，采用纳米压痕试验对刀 片纳米硬度、弹性恢复系数（We）和能量耗散系数（Kd）进行测量，结果发现纳米硬度和显微硬度值接近，渗 B 层的弹性 恢复能力较渗 V 层强，但是渗 V 层表现出更好的塑性变形能力。摩擦试验表明渗 V 层摩擦系数为 0.5，相对渗 B 层的 0.68 更低，但是在非冲击载荷下渗 B 层因为硬度高将具有更好的耐磨性。综合厚度和机械性能考虑，渗 V 层良好的塑性变形能 力将在抗刀头卷刃上更有优势，而渗 B 层因为较高硬度则在稳定负载下具有更好的耐磨性。 [ABSTRACT FROM AUTHOR]

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