On the Abrasion of Ultrafine WC–Co Hardmetals by Small SiC Abrasive

Abrasive wear of a series of WC-(5–14 wt.%)Co hardmetals was investigated employing P800 and P120 SiC abrasive papers. It was found that if fine abradant was utilized, submicron grades demonstrated substantially higher wear rates than the coarse grades. Such a behaviour was associated to different wear mechanisms operating for fine and coarse grades and correlated to the ratio of the abrasive size to size of the hard WC phase.     

Cerium enrichment on sinter skin of mischmetal doped WC-Co cemented carbide

Rare earth-doped WC-Co cemented carbides with low carbon-containing level were prepared by adding mischmetal (mainly containing lanthanum and cerium) in the form of cobalt pre-alloyed powder during ball-milling.After sintering, the sinter skin (exterior) was observed and analyzed by scanning electron microscopy(SEM)and energy disperse X-ray spectroscopy(EDXS). The results show that during the sintering process lanthanum and cerium are separated and cerium predominantly migrates towards the surface forming precipitates containing oxygen.Thermodynamic analysis and polarization of cerium atom caused by the strong interaction between cerium atoms and high energy carbon atoms were used in explaining the observed phenomenon.     

Microstructure and wear properties of YT758/CuZnNi hardfacing materials

Hardfacing materials containing YT758 hardmetal particles cemented by Cu-based alloy was deposited on the substrate to produce milling tools by oxy-acetylene flame process. Microstructure and wear properties of the hardfacing layers were analyzed by scanning electron microscopy （SEM） and electron dispersion X-ray spectroscopy（EDXS） and wear test. The results show that inter-diffusion zone is found at the interface of YT758/CuZnNi, which promises to improve the bonding strength of YT758/CuZnNi. The wear resistance of YT758/CuZnNi hardfacing layers is higher than that of YG8/CuZnNi hardfacing layers. The working efficiency of the milling tools strengthened by YT758/CuZnNi is approximately 2 - 3 times higher than that strengthened by YG8/CuZnNi.     

Abrasion of ultrafine WC-Co by fine abrasive particles

Abrasive wear of a series of WC-（5%-14%, mass fraction）Co hardmetals was investigated employing coarse and fine SiC abrasive under two-body dry abrasion conditions with pin-on-disc and edge-on-disc test arrangements. Unexpectedly, it is found that submicron grades demonstrate substantially higher wear rates comparing with the coarse grades if fine abrasive is utilized in pin-on-disc tests. Such a behavior is attributed to changes in a ratio of abrasive size to size of hard phase as finer abrasive is used. The edge-on-disc test demonstrates that edge wear may be described in two stages with the highest wear rates at the beginning stage. This behavior is associated with a transition of wear mechanisms as edge is wider due to wear. Compared with the ultrafine grades of the same Co content, the coarse grades demonstrate higher wear rates at the beginning, but lower wear rates at the final stage. Wear rates and mechanisms observed at final stage correlate well to the results observed for pin-on-disc tests employing fine abrasive.     

微纳米硬质合金的制备及应用

对适应现代先进制造业的微纳米硬质合金材料的技术研究和实际应用进行了综合评述,总结了微纳米硬质合金材料当前需要解决的关键问题,并指出了其未来的发展趋势.     

镍含量对超细WC-Ni-VC-TaC硬质合金结构和力学性能的影响

采用放电等离子烧结(SPS)方法,结合使用VC和TaC晶粒抑制剂,制备Ni质量分数为6%~10%的超细WC-Ni硬质合金。研究表明,所制备WC-Ni-VC-TaC硬质合金WC晶粒在0.2~0.4μm;合金中含有大量微孔,但微孔大小随合金中粘结相Ni含量增加而减小。且随合金中Ni含量增加,合金中WC晶粒略有增长,合金相对密度先减小后增大,硬度由24500MPa逐渐减小到18600MPa(HV1),但抗弯强度却由1600MPa增大到2140MPa。     

高性能硬质合金刀具材料的研究与开发

超细晶硬质合金(晶粒度≤0.5μm)性能优异,制备技术相对成熟,是高性能的硬质合金刀具材料。从厦门金鹭特种合金有限公司和国家钨材料工程技术中心承担并完成的航空航天钛合金用系列化数控刀具开发以及黑色金属加工用系列化刀具开发的课题经验出发,对该领域材料在中国的研究和开发进行论述。     

Heat Treatment of WC-Co Hardmetals and Transformation Temperature of Cobalt Phase

The Present work has found that the transverse rupture strength of WC-Co hardmetals can be improved by queuching heat treatment. The increment of transverse rupture strength （ΔTRS） was dependent on the cobalt content of hardmetal. The higher the cobalt content of hardmetal is, the more the increment of transverse rupture strength is. The main reason is that the transformation of face centered cubic cobalt stabilized at high temperature to hexagonal close packed cobalt can be depressed by quenching. The transformation temperature of hexagonal close packed cobalt binder phase was determined by differential thermal analysis. It was found that the transformation temperature increases with increase of cobalt content of hardmetal. The reason is that the cobalt binder phase of high cobalt hardmetal contains higher tungsten content than that of low cobalt hardmetal after quenching.