Atomic force microscope study of WC-10Co cemented carbide sintered from nanocrystalline composite powders

In order to compare the spark plasma sintedng （SPS） process plus hot isostatic press （HIP） with vacuum sintedng plus HIP, an investigation was carried out on the topography, microstructure and gain size distribution of nanocrystalline WC-10Co composite powder and the sintered specimens prepared by SPS plus HIP and by vacuum sintering plus HIP by means of atomic force microscopy （AFM）. The mechanical properties of the sintered specimens were also investigated. It is very easy to find cobalt lakes in the specimen prepared by vacuum sintering plus HIP process. But the microstructure of the specimen prepared by SPS plus HIP is more homogeneous, and the grain size is smaller than that prepared by vacuum sintering plus HIP. The WC-10Co ultrafine cemented carbide consolidated by SPS plus HIP can reach a relative density of 99.4%, and the transverse rupture strength （TRS） is higher than 3540 MPa, the Rockwell A hardness （HRA） is higher than 92.8, the average grain size is smaller than 300 nm, and the WC-10Co ultrafine cemented carbide with excellent properties is achieved. The specimen prepared by SPS with HIP has better properties and microstructure than that prepared by vacuum sintering with HIP.

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.

Influences of Carbon Content on the Properties and Microstructure of Ultrafine WC-10Co Cemented Carbide

WC-10Co nanocrystalline composite powders prepared by spray pyrogenation-continuous reduction and carburization technology were consolidated by vacuum sintering plus hot isostatic pressing （HIP）. Influences of carbon content on properties and microstructure of ultrafine WC-10Co cemented carbide were investigated. The results show that the relative density of the ultrafine WC-10Co cemented carbides can reach 99.72%, and the transverse rupture strength （TRS） was higher than 3 890 MPa, Rockwell A hardness （HRA） was higher than 92.5, the average grain size was less than 460 nm, when carbon content in nanocrystalline composite powder was 5.54wt% and the ball-milled time was 48 hours, ultrafine WC-10Co cemented carbide with excellent properties and homogeneous microstructure was 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.