紫钨生产的亚微米级钨粉和碳化钨粉的形貌

用紫钨可以生产出亚微米级的钨粉和碳化钨粉。通过不同的制样手段 ,使用透射电镜和扫描电镜研究了用紫钨生产的钨粉和碳化钨粉的形貌变化。发现钨和碳化钨粉形状复杂 ,多为树枝状或链状颗粒团形式 ,碳化钨粉中有较多的晶体缺陷。     

Cu、Nb对多元Fe基非晶合金的形成及热稳定性的影响

以具有宽过冷液相区成分的Fe-Al-Ga-P-B-（C）-Si合金作为研究对象，研究了Cu、Nb元素及其加入量对合金非晶形成能力和热稳定性的影响。结果表明，当Cu加入量超过2％（原子百分比）时，合金中有晶化相析出，而低于2％时则表现为完全的非晶态。与不加铜的非晶合金相比，含铜非晶态合金的玻璃转变温度瓦和晶化温度瓦均向高温区移动，过冷液相区△Tx减小，表明非晶合金的热稳定性下降。在非晶合金形成方面．Nb也有类似的效果。含铌0、5％合金的过冷液相区△Tx大于不含铌元素的合金，表明具有较大的玻璃形成能力和稳定性。     

C11300(T3)基体亚音速火焰喷涂层特性的研究

采用亚音速火焰喷涂技术，在C11300(T3)基体表面分别喷碳化钨弥散型钴基和NiCrBSi2种类型的自熔性合金。采用扫描电镜(SEM)和X射线衍射(XRD)等测试方法研究基体与喷涂层之间的界面结合状况、显微组织和喷涂层的物相结构。试验结果表明，基体与喷涂层界面结合状况良好，且存在相互扩散现象，界面处基体组织细化。喷涂过程中碳化钨发生少量热分解和脱碳反应，生成W2C；涂层MCrBSi中有大量均匀分布的点状CrB生成。随着合金粉末中碳化钨含量的增加，涂层的硬度和耐高温性能也明显提高。     

超细WC粉末的强化球磨和表面钝化

研究了超细WC球磨破碎和分散机理,通过表面活性剂和聚合物的添加,降低了超细WC的球磨料浆粘度,提高了WC的球磨效率;经过150小时球磨后WC的BET小于100nm,X衍射晶粒度小于30nm。WC表面聚合物包覆的物理改性,其抗氧化能力提高了一倍。     

火焰喷涂碳化物涂层的耐磨性研究

对碳化物复合粉末热喷涂工艺和Ni基自熔合金粉末热喷焊工艺进行了研究，在低碳钢基体上分别采用氧-乙炔火焰喷涂Co包WC粉末、Ni包WC粉末，以及火焰喷焊Ni60、Ni60 20％WC自熔合金工艺获得耐磨合金涂层。研究了涂层的显微结构和相特征以及耐磨性。结果表明，在喷焊Ni60 20％WC粉末涂层的组织中，由于加入了WC粒子，有效改善了涂层的显微组织和性能，得到了喷焊质量和耐磨性俱佳的合金涂层。     

Consolidation of Cr3C2 doping WC–1TiN–5MgO micro–nano composites by two-step sintering

The effect of Cr₃C₂ additions on WC–1TiN–5MgO composites by two-step hot-pressing sintering (heated to 1750°C and then immediately cooled to 1575°C with a soaking time of 60?min under a sintering pressure of 50?MPa) was comprehensively investigated. The microstructure was characterized by means of scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), and X-ray diffractometry (XRD). Mechanical properties, such as hardness, transverse rupture strength, and fracture toughness, were measured. The experimental results show that no η-phase or brittle phases such as W₂C were formed, and excellent mechanical properties were achieved for 0.6?wt.% Cr₃C₂ additions with a hardness of 24.76?GPa, a flexural strength of 1257.1?MPa, and a fracture toughness of 10.08?MPa?·?mm^1/2. Cr₃C₂ addition brought about an improvement in the sinterability and contributed to the homogeneous distribution of second phase nanosized MgO. Crack deflection and crack bridging are the major mechanisms contributing to the drastically enhanced flexural strength and fracture toughness.     

Alloy design of a cost-effective and castable heat-resistant iron alloy

A new heat-resistant Fe-based cast alloy has been designed making the best use of the CALPHAD method. The objective was to replace the material for precision cast products made from Ni-based superalloys with improved Fe-based alloys originally developed for lower temperature applications.The key to the design is to balance the amount of strengthening ${\gamma }^{\prime }$- Ni₃(Ti,Al) precipitates and brittle $\sigma$ phase, and to simultaneously decrease as-cast microsegregation. Contours of the equal phase fraction were calculated over the isothermal diagrams of the Fe–Ni–Cr–Ti–Al–Nb system, and provided useful guidelines for compositional modifications. The microsegregation was also evaluated by Scheil-type simulation in order to reduce micropores caused by oxidation of the solidifying front.The developed cast Fe-based alloy showed desirable strength at the envisioned service temperatures and filled the open range of heat resistance between Ni-based superalloys and the original alloy.     

Corrosion of amorphous and nanocrystalline Fe-based alloys and its influence on their magnetic behavior

Nanocrystalline soft magnetic materials with low coercivity, high saturation magnetization and high permeability are commonly used as cores in transformers and generators in stress and field sensors. The influence of factors connected with corrosion is almost impossible to eliminate. In the present work, a comparative study of the electrochemical behavior of Fe₇₈Si₁₃B₉ and Fe_73.5Si_13.5B₉Nb₃Cu₁ amorphous and nanocrystallized alloys, tested in 0.5 M NaCl solution, has been performed by linear polarization and electrochemical impedance spectroscopy methods. Changes of magnetic properties including coercivity, induction and magnetic retentivity were analyzed. These properties were investigated as a function of the structure of primary amorphous ribbons and as a function of corrosion environment type, in which longitudinally and transversely cut ribbon specimens were exposed for 15 days. The best magnetic properties were found for the Fe₇₈Si₉B₁₃ ribbon after a structural relaxation at a temperature of 350 °C for an hour and for the Fe_73.5Si_13.5B₉Nb₃Cu₁ ribbon after a primary crystallization at a temperature of 550 °C for an hour. Corrosion did not cause the direct degradation of the magnetic properties of the Fe₇₈Si₉B₁₃ and Fe_73.5Si_13.5B₉Nb₃Cu₁ alloys. The corrosion processes occurring on the surface of the Fe_73.5Si_13.5B₉Nb₃Cu₁ alloy ribbon with the amorphous structures improve induction B_s. Most probably it is connected with the decrease of undesirable stresses blocking a motion of magnetic domain walls on the ribbon surface. Changes of corrosion mechanism depending on structure and applied solution were analyzed. The electrochemical impedance experiment were performed at open circuit potential for amorphous and nanocrystalline specimens. Two electrochemical corrosion mechanisms of Fe_73.5Si_13.5B₉Nb₃Cu₁ alloy in 0.5 M NaCl solution were found. Charge transfer control mechanism is typical for amorphous (as received) alloys. Mixed mechanism-mass transport and charge transfer controlled was observed for nanocrystalline Fe_73.5Si_13.5B₉Nb₃Cu₁ alloy.     

超细碳化钨粉末粒度测试方法的研究

应用显微镜法(SEM、TEM)、激光粒度法、X射线线宽法、比表面积法对自制超细碳化钨粉末粒度进行测量,探讨了测量原理、颗粒形状等因素对粒径测试准确度的影响。通过对实验结果的分析,研究对比了几种超细微粒表征手段的优越性和局限性。