火花等离子烧结技术制备的WC/Co纳米硬质合金

研究了火花等离子烧结工艺与YG10、YG12两种纳米硬质合金性能的关系.然后采用火花等离子烧结技术制备了硬质合金功能梯度材料,该材料由纳米WC/10%Co、纳米WC/12%Co、微米WC/15%Co混合粉以及不锈钢圆片烧结而成.显微硬度压痕显示该材料各层间的应力较小.     

涂层硬质合金回收料生产硬质合金的工艺探索

利用废旧涂层硬质合金回收料生产硬质合金,通过采用适当的工艺方法,可以生产出质量较好的再生硬质合金产品。     

YG8与TA15真空扩散焊

采用ANSYS软件对YG8与TA15真空扩散焊接头残余热应力进行三维瞬态有限元数值模拟，验证了Cu作为中间层材料在缓解YG8／TA15接头热应力方面的作用。在焊接温度为860℃与880℃，压力为5MPa，扩散焊时间为60min的条件下，进行YG8与TA15的真空扩散焊，分析了YG8与TA15连接界面的微观组织形貌。结果表明，YG8／Cu界面呈一条深色曲线，结合良好；而TA15／Cu界面生成呈层状分布的脆性Ti-Cu金属间化合物，将会影响到接头的整体性能，故对其在结合界面的体积与分布状态必须予以控制。     

Stress,strength, and durability analysis of gradient-structured hardmetal products

We present results of finite-element analysis of stressed state in a percussive-rotary drilling bit fitted with hardmetal inserts during its contact interaction with rock, allowing for brazing-induced stresses. The most likely fracture zones in inserts have been identified. Based on the proposed criterion for fatigue strength of structurally inhomogeneous materials, the binder composition of the inserts has been optimized for the longest service life. It is demonstrated that the formation of a gradient structure in a hardmetal, whereby the material preserves its initial mechanical properties in the main volume but has an increased ultimate tensile strength in zones where tensile stresses are involved, results in a longer service life of the hardmetal products and a noticeably diminished dependence of their cyclic strength on the scale factor. __________ Translated from Problemy Prochnosti, No. 2, pp. 15–31, March–April, 2007.     

碳化钨基硬质合金控碳问题探讨

以ＷＣ的两种控碳标准（即饱和碳标准与非饱和碳标准）为基础，分析讨论了与之相应的ＷＣ基硬质合金控碳方法的优劣，并对硬质合金本身的控碳水平进行了探讨。     

YG15硬质合金抗弯强度的数学解析

应用数学方法分析了YG15硬质合金抗弯强度的实验结果。叙述了用一组有限个试样的结果估计硬质合金总体强度分布的原理和方法,对得出的分布特征参数的物理意义作了探讨。发现置信边值强度既包含了实验结果的平均值又反映了分散程度,能更可靠地表征合金的强度水平,可作为材料强度性能的评价指标。并用该强度指标有效地体现了热等静压对硬质合金强度的作用。     

On the contiguity of carbide phase in WC–Co hardmetals

In this paper the analysis of dependence of carbide phase contiguity in WC–Co hardmetals on the variation coefficient of WC grain size distribution is carried out. The relationship proposed is

C=1−V_Co^0.644exp(0.391V)

Here C is the contiguity, V_Co is the volume fraction of binder and V is the coefficient of variation. This relation is obtained on the basis of experimental data available in the literature. The basic meaning of this model is that with its help one more microstructural parameter V is introduced explicitly. This parameter essentially affects the mechanical behaviour of WC–Co hardmetals.     

硬质合金钎焊接头的拘束强化

从力学观点分析了高温高压扩散处理硬质合金钎焊接头的拘束强化效应。文中指出，钎焊接头受力时，钎缝的拘束应力状态与双边半圆缺口平板中的应力状态相类似，据此，在一定范围内建立了钎缝宽度与接头强度间的定量关系，为通过控制钎缝宽度以提高接头强度提供了依据。     

Investigation of micro-scale abrasion–corrosion of WC-based sintered hardmetal and sprayed coating using in situ electrochemical current-noise measurements

The micro-scale wear–corrosion interactions of WC-based sintered hardmetals and sprayed coatings are typically investigated by comparing the wear-rates in corrosive environments with neutral (pH 7) conditions and inferring electrochemical activity. However, for a greater understanding of the wear–corrosion interactions, there is a need to examine the repassivation kinetics during micro-abrasion tests under different pH conditions. This paper details in situ electrochemical current-noise measurements performed using a modified micro-abrasion tester to elucidate these wear–corrosion interactions for pH 7–13 conditions for sintered WC–5.7Co–0.3Cr and sprayed WC–10Co–4Cr specimens. Electrochemical measurements and SEM micrographs of worn surfaces are used to detail the degradation process. Discussion will focus on the wear–corrosion interactions present under neutral and alkaline conditions for sintered and sprayed specimens and the influence of microstructure on the electrochemical activity will be detailed.     

Influence of Ca ions and temperature on the corrosion behavior of WC–Co hardmetals in alkaline solutions

The effect of temperature and Ca ions on the corrosion behavior of hardmetals was investigated in 0.1 M NaOH and 0.05 M Ca(OH)₂ alkaline electrolytes using impedance spectroscopy, potentiodynamic polarization and surface analytical techniques. It was found that calcium containing alkaline solutions efficiently decrease the anodic currents up to 5 times by forming a calcium containing deposit on the top of the WC–Co hardmetal surface, which remains stable even at higher temperatures (40 °C and 60 °C). This positive influence of Ca ions is predominant under polarization in the range from 0 to +0.85 V (Ag/AgCl) but is not apparent under OCP conditions. In NaOH, however, the corrosion resistance strongly decreases at higher temperatures as compared with the room temperature. At the slightly elevated temperature in 0.1 M NaOH the Co binder phase loses its passivity and is almost completely washed out of the compound material. A WC skeleton remains on the surface and hence the ductility in the hardmetal is lost. In the end, the material could completely fail under such operating conditions. Also the Ni alloyed binder loses its strong passivation ability at the elevated temperatures.