Ultra-coarse grain cemented carbide secondary liquid-phase sintering process

Abstract

The invention discloses an ultra-coarse grain cemented carbide secondary liquid-phase sintering process which is divided into four phases: I. a dewaxing phase; II. a vacuum sintering phase; III. a pressure sintering phase; IV. a cooling phase; wherein during the vacuum sintering of the phase II, the process comprises the following steps: heating to a final sintering temperature, performing heat preservation for 10-40 min, then cooling to reach a temperature below a liquid phase point with a rate of 4-6 DEG C / min, performing secondary heating to the final sintering temperature with a rate of 2-4 DEG C / min, performing heat preservation for 10-40 min, and performing pressure sintering of the phase III. The invention effectively solves the problems of porosity and Co pool for ultra-coarse grain cemented carbide without the increase of the sintering temperature, prevents macropores (larger than 25 microns), reduces microscopic porosity, controls the porosity to be within the A02B00 level, and provides the prepared products with more uniform WC crystal grains, improved product performance, and increased service life.

Description

technical field [0001] The invention relates to a secondary liquid-phase sintering process of ultra-coarse-grained hard alloys. Background technique [0002] In the production process of ultra-coarse-grained cemented carbide mixture, while ensuring the uniform mixing of WC / Co powder, in order to reduce WC breakage and ensure the WC particle size of the sintered product, light ball milling technology is adopted. In the mixture prepared by this technique, the surface activity of WC and Co is poor. [0003] While the existing traditional sintering process curve such as image 3 shown. Sintering is mainly divided into four stages: I: dewaxing stage; II: vacuum sintering stage; III: pressure sintering stage; IV: cooling stage. In the existing traditional sintering process, in the stage II vacuum sintering stage, the temperature is raised to the final sintering temperature (the sintering temperature of ultra-coarse-grained cemented carbide is generally 1380-1500°C), and then the...

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Problems solved by technology

And with the increase of sintering temperature, the amount of liquid phase increases during the high-temperature sintering process of the product, resulting in sintering deformation of the product and difficulty in controlling the size of the product

[0005] In short, the ultra-coarse-grained cemented carbide products sintered by the traditional process are very easy to appear Figure 1a , Figure 1b , Figure 2a and Figure 2b The structural defects shown affect the service life of alloy products

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