Technology Preparation Of Nanocrytalline WC-Co Composite Powder By Spray-drying、Low Temperature Reduction-carbonization Process

Cobalt tungsten carbide composite powder and its alloys is extremely importantfunctional materials in modern industrial, defense and new technologies,it is widely used inaerospace, marine, automotive, electrical, electronics, chemical and other areas. Experimentalresults showed that if the cemented carbide grain be finer then the comprehensiveperformance will be better. Especially when the grain size less than0.5m, hardness andstrength will be greatly improved. Moreover, Surface spraying hard-facing materials put ahigher standard on composite powder, not only requires small uniform particle size, but alsorequires the shape, liquidity and hardness of powder.Spray Conversion Process made nanometer WC-Co composite powder is first proposedby the American Rutgers university in1992, which can dissolved the Tungsten soluble saltand cobalt salt to a composite solution with water.Made the chemical composition ofprecursor powder evenly by spray-dried and then hitches in high temperature fluidized bedreduction carbonization nanoscale WC-Co composite powder. This method has thecharacteristics of powder is easy to adjust, powder mixing evenly, narrow particle sizedistribution and components are adjustable, but requires complex high temperature fluidizedbed equipment, large energy consumption and the process control is difficult, so that itdifficult to product Industrial. The improvement of the method which can make nanometerand ultrafine WC-Co composite powder has become a hot spot. This project is carriedforward based on this purpose.With organic carbon and ultra pure carbon black as carbon source, soluble salt tungstenand cobalt salt as raw materials, by the preparation of tungsten cobalt compound salt solution,spray drying, low temperature reduction carbonization can made nanocrystalline WC-Cocarbide composite powder. The reaction mechanism of low temperature reductioncarbonization process, Catalysis of Co, the effect of carbon sources and the Analysis of thedifferent stages of the composite powder in different stages of the composite powdermorphology, phase were analyzed. The preparation process of WC-Co made of superfinecrystalline cemented carbide composite powder.With high carbon YHC-86type tester, CS-800infrared carbon sulfur analyzer tomeasure total carbon powder, free carbon content; With LECO-TC600nitrogen oxygen meter measuring oxygen content of powder; Use ZSX Primus Ⅱ X-ray fluorescence spectrum(X-ray fluorescence analysis) instrument measuring powder Co, Fe content; Use PL4-type1powder apparent density gauge measuring the apparent density of the powder; Mastersizerparticle size analyzer2000powder particle size distribution measurement; In JMS-6701-ftype on the field emission scanning electron microscopy (sem) observation and its alloypowder morphology; With D/Max2550vb type X ray diffraction analysis of powder phase.Through the project shows that two kinds of carbon source can be prepared with aparticle size in100~200nm nanocrystalline WC-Co composite powder, the compositepowder into a shell of spherical structure, shell sphere size is between30~50m; and got alot of porosity and larger specific surface area; The catalysis of Co and shell of sphericalpowder structure is beneficial to reduce the reduction carbonization temperature andacceleration response; C content affected by reducing gas flow rate and carbonization timesignificantly, which is the key to the composite powder quality control; In preparation ofnanocrystalline WC-Co organic carbon composite powder was successfully the grain size in0.4mu m ultrafine silicon carbide, the bending strength of4283Mpa, rockwell hardness(HRA) of93.2.