Effects of (Ti,Ta,Nb,W)(C,N) on the microstructure,mechanical properties and corrosion behaviors of WC-Co cemented carbides

Homogeneous solid-solution (Ti, Ta, Nb,W)(C,N) powders were synthesized through carbothermal reduction-nitridation method. The effects of (Ti, Ta, Nb,W)(C,N) powders on the microstructure, mechanical properties and corrosion resistance of WC-10Co cemented carbides were investigated using XRD, SEM, electrochemical test and mechanical properties tests. The results showed that cemented carbides with pre-alloyed powder addition had a similar microstructure appearance: weak core/rim structure consisting of solid-solution phase embedded in the WC-Co system. The black core and gray rim, both of which contained similar elements, were identified as (Ti, Ta, Nb,W)(C,N), but the latter contained higher amount of heavy elements.With the addition of (Ti, Ta, Nb,W)(C,N) powders, the density, transverse rupture strength and fracture toughness of samples decreased monotonously. However, the hardness rose sharply at first, reached a peak at 15 wt% solid-solution addition, then slightly decreased, and finally increased again. Results also revealed that increasing (Ti, Ta, Nb,W)(C,N) made the open circuit potential (OCP) in 1 M sulphuric acid solution more negative than that of WC-Co, and all specimens exhibited pseudo-passivation phenomenon in the test solution. In addition, increasing pre-alloyed powders led to decreasing corrosion current density, which implies that (Ti, Ta, Nb,W)(C,N) could remarkably improve the corrosion resistance of WC-Co cemented carbides.     

石英砂掺量对膨润土–砂混合物泥浆样干缩开裂的控制机制

高放废物地质处置工程中,膨润土–砂混合物作为缓冲回填材料的干缩开裂特征对工程屏障的安全性有重要影响。以混合型缓冲回填材料为研究对象,分别制备掺砂率为0%～50%膨润土–砂的浆状试样,通过室内恒温干燥试验,研究混合物的干缩开裂特征。结果表明:当掺砂率小于30%时,混合物的收缩曲线与径向应变曲线均基本重合,石英砂悬浮在膨润土中,混合物的干缩开裂特性由膨润土决定;当掺砂率大于30%时,混合物中石英砂逐渐相互接触,增加了颗粒间的摩擦力且有大孔隙形成,进而能够抑制混合物的干缩开裂。石英砂颗粒的相互接触显著提高了混合物进气值,略微提高了缩限,限制了混合物的干燥收缩。大孔隙的形成导致毛细水作用力的降低;颗粒间摩擦力的增加,增强了混合物抵抗断裂的能力,进而抑制了混合物干燥裂隙的发展。最终确定了抑制膨润土–砂混合物干缩开裂的最低掺砂率为30%。     

公路桥涵台背回填施工的质量控制

由于公路与桥涵连接处是整个公路施工过程中的重要施工点,根据桥涵台背回填处施工难度大、质量不易控制的情况,分析了可能产生跳车的原因,提出了在材料、施工准备、施工控制、检测等阶段进行质量控制的措施.     

强夯法在碎石填土地基处理中的应用

简要介绍了强夯法加固岳阳石油化工总厂技改工程碎石填土地基的情况，并对一些有关问题进行了讨论     

无填料振冲法加固粉细砂地基试验研究及应用

结合上海市某重点工程，基于粉细砂的工程特性，通过改进和革新传统的振冲工艺及施工参数，对级配较差的饱和疏松粉细砂地基采用无填料振冲加固的有效性和相应的工艺参数进行了现场试验研究，并探讨了振冲加固后粉细砂土强度的时间效应问题。试验和大面积地基加固实践证明，只要采用正确的施工工艺和参数，对于饱和疏松粉细砂地基，采用无填料振冲法加固效果显著，加固后粉细砂可以达到中密甚至密实状态。试验和实践为无填料振冲法在同类地基中的推广应用及相应规范的制定或修改提供了一些成功的经验。     

水源热泵设计应用问题

水源热泵是许多生产厂家大力宣传的一项节能技术。文章从系统的角度,分析了水源热泵系统的应用过程,提出水源热泵系统应该考虑地下水水温水质及土壤含水层的性质,设置合理的空调水系统才能节能。论述了水源热泵系统使用过程中常见的问题及利用水源热泵同时供冷与供热的问题。     

深回填土和岩溶发育地基桩基合理应用实例分析

对岩溶发育和深回填土地基基础选用进行了比选 ,并对所选活瓣桩尖振动沉管灌注桩在设计与施工方面提出了技术措施 ,最后阐述了深回填土地基选用活瓣桩尖振动沉管灌注桩的良好效果 ,其成果可供同类工程的设计施工利用和参考     

强夯法和振冲法处理松细砂地基的应用比较

结合某松细砂地基加固工程，对低能量强夯法和无填料振冲法处理松细砂地基的适用性及加固效果进行了试验研究，并对它们的适用范围、优缺点进行了比较分析。试验表明，只要采用正确的施工工艺和参数，采用低能量强夯法和无填料振冲法加固饱和松细砂地基都能取得显著效果。     

Wear characteristics of cemented carbide tool in dry-machining Ti-6Al-4V

In machining titanium alloys, due to the low thermal conductivity and high chemical activity of titanium alloys, tool wear is serious and processing efficiency is very low. To avoid the effects of impurities, which were brought by the cutting fluid, the uncoated cemented carbide tool (WC-Co), which was suitable for cutting titanium alloys, was used for the experiments of dry-turning titanium alloy Ti-6Al-4V. A scanning electron microscopy (SEM) equipped with energy-dispersive X-ray spectrometer (EDS) was used to analyze tool wear mechanism. Based on analyzing the friction characteristic of tool–chip interface, tool wear mechanism was also studied and a physical evolution model of tool wear was established. The results showed that there existed serious adhesion, diffusion and oxidation at tool–chip interface and increasing cutting speed accelerated their occurrence. The physical evolution of tool wear behavior can reflect the loss process of tool material very well.     

全尾砂结构流体胶结充填的理论与实践

随着对矿产资源不可再生性的认识加深及环境保护要求的日趋严格,全尾砂充填在金属矿山的应用越来越普遍。论述了国内外全尾砂充填现状,提出了全尾砂结构流体充填方法。在实验室试验的基础上,进行了全尾砂结构流体流变参数的测定及输送性能的理论分析计算。结合矿山充填实践,介绍了该种充填方式的工艺流程及其应用效果。