An improved wax-based multi-component binder and a new debinding method termed high-pressure condensed solvent extraction were developed for powder injection molding of tungsten cemented carbide. The results indicate that a critical powder loading of 65% (volume fraction) and an ideal rheological properties were obtained by the feedstock based on the binder. High debinding rate and specimens with high strength were obtained by the debinding method. Moreover, by making high temperature holding time adjustable, it makes the subsequent thermal degradation process more flexible to debinding atmosphere and carbon content of the as debinded specimens controllable. The transverse rupture strength, hardness and density of the as-sintered specimens made by an optimized PIM process are 2.48GPa, HRA90 and 14.72g/cm3, respectively. Good shape retention and about 0.02% dimension deviation were achieved.

The invention relates to a binder for injection molding of titanium alloy powder and a method for injection molding of titanium alloy parts, belonging to the technical field of titanium alloy parts processing. The binder is composed of polypropylene, low density polyethylene, paraffin, stearic acid and naphthalene.

The method is as follows: the spherical powder of titanium alloy is put into the mixer for heat preservation and preheating, polypropylene and low density polyethylene are put in; The temperature was lowered to 50 degrees for heat preservation, component B was added, the rotating speed was adjusted for mixing, and the temperature was lowered to toothpaste shape for extrusion granulation. Then, injection molding, degreasing, vacuum sintering and furnace cooling were carried out successively to obtain titanium alloy parts. The advantages of the invention is: the existing basic load between 55% ~ 65%, the invention adopts a load of 68%, reduce the proportion of the binder, can say, in the process of feeding with high loading capacity also can guarantee the mixture has good rheological properties, filling, easy to get green for mold shape, and no defects.

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The effects of a new type of grain growth inhibitor on vacuum sintering behavior of nanograined WC-10Co powders produced by mechanical alloying as well as its affecting mechanism were investigated. The results show that the new grain growth inhibitor can promote sintering densification process. Adding the new inhibitor to traditional transitional group element carbides, composite inhibitors become much more effective, obviously induce oriented WC grain growth and evidently encumber plate-like WC grain formation during sintering. For WC-10Co0.8VC/Cr3C2powders with 0.1% of the new additive, the density of 14.48 g/cm3can be achieved after sintering at 1 375degrees for 30 min, corresponding to the grain size of 160 nm and the micro-hardness of 2.150 GPa.

Cemented carbideis a kind of hard and brittle composite material which is different from soft metal material and hard and brittle ceramic material. Due to the different content of soft metal phase and hard phase in the material, the microstructure of the material is different, resulting in the different grinding performance of the hard alloy. The excellent physical and mechanical properties of cemented carbide contribute to the application of this kind of material in engineering, but the high hardness and high wear resistance also make it very difficult to grind it. The purpose of this project is to apply the high speed grinding technology to the processing of hard alloy, deeply study the grinding mechanism of hard alloy and the grinding mechanism of high speed grinding, and provide an effective scheme, experimental basis and theoretical basis for the solution of this difficult problem.

VC and Cr3C2 with different content of grain growth inhibitors were added to the ultrafine WC Co composite powder. The phase composition of the powder and cemented carbidewas analyzed by X-ray diffractometer. The morphology of cemented carbide was observed by SEM and TEM, and the effect of different content of grain growth inhibitors on the microstructure and mechanical properties of cemented carbide was studied. The results show that with the increase of the inhibitor of grain growth, the abnormal grain growth disappears and the grains are fine and uniform; meanwhile, it is found that the increase of VC in WC Co composite powder can rapidly improve the hardness of cemented carbide, while the appropriate amount of Cr3C2 can effectively improve the transverse fracture strength of cemented carbide.

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Most hulls of the ships are protected with paintings, sacrificial anode, and impressed current cathodic protection methods against corrosion problems. However, these conventional methods are not very effective because the rudder of ships stern are exposed to very severe corrosive environment such as tides, speeds of ships, cavitations and erosion corrosion. The environmental factors such as cavitation and corrosion will cause damage for materials with the shock wave by the creation and destruction of bubble. To solve these problems, the cavitation and electrochemical experiments are executed for thermal spray coating with Al−Zn alloy wire material. Thereafter, and sealed specimens with F−Si sealer on Al−Zn alloy coated specimen are executed to improve electrochemical and anti-cavitation characteristics in sea water. The application of fluorine silicon sealing after spray coating of 15%Al−85%Zn seems to be appropriate not only in static environment but also in dynamic environment.

Thermal spray coatingpresents a sacrificial-anode cathodic protection method since differences between the potentials of materials are employed. If a base metal is exposed to seawater, due to defect in the thermal spray coating, the metal is protected by the sacrificial anodic characteristics of the coating layer because micro-cells formed by the base metal and the thermal spray coating act as cathodes and anodes, respectively. The coating thickness has little effect on the surface morphology of the coating. However, the electrochemical properties with the increasing of coaBased on the excellent properties of nano coating, the preparation process of nano YSZ thermal spraying powder was studied. After spray drying, the fluidity, bulk density and microstructure of the aggregates were measured and analyzed by Holzer leak method and electron scanning microscope respectively. It is found that the higher the solid content, the better the fluidity and bulk density of the powder, but the higher the solid content will affect the granulation effect; in the case of a certain solid content, the better the fluidity of the agglomerated powder is after the slurry with moderate binder content is granulating. In order to obtain better agglomerate powder, the reasonable follow-up treatment method is plasma densification under the condition of 300A current and 40V voltage.ting thickness present good results.

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