Research on Ultrafine WC-10Co Cemented Carbide with High Propertie

WC- 10Co nanocomposite powder produced by spray pyrolysis-continuoas reduction and carbonization technology was used, and the vacuum sinteriag plus sinterhip process was cdopted to prepare ultrafine WCCo cemented carbide. The microstructure, grain size, porosity, density, Rockwell A hardness （ HRA ）, transverse rupture strength （ TRS ） , saturated magnetization and coercivity force were studied. The experimental results show that average grain size of the sample prepared by vacuum sintering plas sinterhip technology was about 420 nm, transverse rupture strength was more than 3460 MPa, and Rockwell A hardness of sintered specimen was more than 92.5. Ultrafine WC- 10Co cemented carbide with high strength and high hardness is obtained.

Research of Ultrafine Cemented Carbides for PCB Microdrills

The nanocrystalline WC-10Co composite powders were produced with the processing method of spray thermal decomposition-continuous reduction&carburization.The grain growth inhibitors of 0.4wt%Cr_(3)C_(2) and 0.4wt%VC were added into the composite powders to obtain advanced ultrafine hardmetals with minimal porosity,defects and discontinuous.The rod samples were formed by extrusion.They were sintered in cacuum with SIP treatment.The sintered rods were made into PCB microdrill samples after polishing.Mechanical properties(such as density,hardness,transverse rupture strenth(TRS),magnetic saturation induction and magnetic coercivity)of the sintered ultrafine cemented carbides were measured.The microstructures of them were investigated by scanning electron microscopy(SEM)and transmission electron microscopy(TEM).The experimental results show that the transverse rupture strength of the samples sintered in vacuum with sinterhip(SIP)treatment is more excellent.The grain size could be controlled in a range of 200-400 nm with the help of grain growth inhibitors.And the superfine grained materials have superior strength(3900 MPa)and high hardness(HRA=93.3).These features are ideal for PCB microdrills.

WC-10%CoCrFeNi硬质合金的磨损与腐蚀性能

为解决WC-Ni硬质合金力学性能与耐腐蚀性能间的矛盾,以CoCrFeNi高熵合金作为黏结相制备了WC-10%CoCrFeNi硬质合金。利用维氏硬度计、摩擦磨损试验仪、电化学工作站、扫描电子显微镜、X射线衍射仪等,对WC-10%CoCrFeNi与WC-10%Ni硬质合金的磨损与腐蚀性能进行研究比较。结果表明,与WC-10%Ni硬质合金相比,WC-10%CoCrFeNi的硬度和断裂韧性值较高,干摩擦滑动磨损过程中具有较低的摩擦因数和磨损率,在以3.5%NaCl溶液为介质的电化学腐蚀过程中表现出优异的耐腐蚀性能。

Sintering of WC-10%Co nano powders containing TaC and VC grain growth inhibitors

WC-10%Co （mass fraction） nanocomposite was synthesized by high energy planetary ball milling at balls to powder mass ratio of 15. For inhibition of growth of WC grains during sintering, TaC and VC were used as inhibitors. Hardness and fracture toughness results reveal that the addition of TaC increases the toughness of hard metal and VC increases the hardness of the sample due to the effective reduction of WC grain size. The effect of co-addition of 0.6% TaC and 0.7% VC on physical and mechanical properties of WC-10%Co sintered sample was investigated. The hardness of the sample is increased to HV30 1 787, which is 24% more than that of the inhibitor-free sample; the fracture toughness achieves 8.7 MPa·m^1/2, 35% higer then that of the inhibitor-free sample; the grain growth is inhibited and grain size achieves 0.38μ m.

Influence of Deep Cryogenic Treatment on Microstructures and Mechanical Properties of an Ultrafine-Grained WC-12Co Cemented Carbide

Effect of deep cryogenic treatment （DCT） on the microstructures and mechanical behavior of ultrafine-grained WC-12Co cemented carbide was investigated by using XRD, SEM, and DSC. The phase transformations of pure Co and binder phase Co in cemented carbide were analyzed in detail to correlate the strengthening mechanism with its x -ε, phase transition. The results show that DCT resulted in a slight increase in hardness and bending strength of ultrafine- grained WC-12Co cemented carbide. For the ultrafine-grained cemented carbide after DCT, there is no significant change in the microstructure and the elemental distribution of the cemented carbides, but the fractured morphology shows a feature of plastic deformation. In the cases of pure Co and the binder phase Co in WC-12Co cemented carbide, they exhibit different features of phase transformation. The improvement of mechanical property of cemented carbide can be attributed to the increased amount of ε-Co in WC-12Co composites after DCT.

Ni-Fe-C ALLOY EFFECT ON η PHASE FORMED DURING TIG WELDING OF WC-Co WITH 45 STEEL

Ni-Fe-C filler metal based on WC-30Co/Ni-Fe-C/45 steel is developed using TIGwelding method. The weld joints are studied by means of optical microscope, SEM, EPMA, X-rays andmicro hardness test etc. The results show that the weld joints of WC-30Co and 45 steel can beobtained by TIG welding using Ni-Fe-C alloys as filler metals. The harmful eta phase formed in thejoints is M_6C, M_(12)C type carbides. The poor carbon content of the W-Co-C system resulted fromthe carbon diffusion and the high ingredient Fe are the two vital factors inducing to eta phaseformation. It could be restricted by the addition of carbon element into Ni-Fe alloys.

晶粒长大抑制剂对硬质合金性能的影响

系统研究了不同粒度和不同配比量的晶粒长大抑制剂Cr3C2和VC单独添加或复合添加时,对WC-10%Co超细硬质合金力学性能和显微组织的影响。研究结果表明,WC-10%Co超细硬质合金的硬度随着晶粒长大抑制剂加入量的增加而升高,而随着晶粒长大抑制剂粒度的细化,硬度的最大值则存在对应的抑制剂粒度点;复合添加抑制剂m(VC)∶m(Cr3C2)=3∶2左右时,所得成分为WC-10Co-0.6VC-0.4Cr3C2,合金的综合性能较好,抗弯强度可达2954MPa,硬度HRA为91.9。

碳化钨粗细颗粒搭配对WC—10%Co合金力学性能与组织结构的影响

本实验系统地研究了碳化钨粗颗细粒搭配对WC—10%合金的力学性能与组织结构的影响.优质碳化钨粉,通过空气分级的方法获得三种不同粒度级别的碳化钨.不同粒度级别的碳化钨,以适当的比例搭配和钴粉混合.获得具有“双重晶粒结构”的硬质合金,在凿岩试验中取得了良好的结果.