Vacuum Sintering of Metal Matrix Composites

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Metal matrix composites have attracted the attention of scholars and researchers from all over the world due to their high specific strength, specific stiffness, good thermal stability, wear resistance, dimensional stability and composition design. hot spot. At present, steel matrix composites are mainly prepared by casting infiltration method, centrifugal casting method and powder metallurgy method. In the field of powder metallurgy, warm press sintering is a relatively new technology, which uses metal powder and special lubricant (polymer) to press and sinter at a temperature higher than room temperature (about 130-150 ° C), which can obtain high Density products, and the cost is only slightly higher than the conventional powder metallurgy process. The temperature of temperature and pressing is generally controlled at 25-85°C above the glass transition temperature of the polymer lubricant or 5-50°C below the melting point, and the lubricant is in a viscous flow state at this time.

Process flow:
The matrix of the composite material is 45 steel powder (the 45 steel powder is prepared with pure iron powder and graphite powder according to the proportion of iron and carbon in the 45 steel, and is made by ball milling), the reinforcing particles are cast WC particles, and the lubricant is polyvinyl alcohol and stearic acid. zinc. The mass ratio of WC and 45 steel is 1:1, the particle size of WC particles and 45 steel powder is 0.076-0.10 mm, and the mass fraction of lubricant is 0.6%.

Composite material sample preparation: The preparation of steel matrix composite materials by powder metallurgy vacuum sintering method is mainly divided into the following key steps; powder mixing, compact pressing, vacuum sintering, and post-heat treatment.

(1) Powder mixing; dry mixing the mixture in a HF-G70-R75s2 type ball mill for 20h, and the ball mill rotation speed is selected as 250r/min.

(2) Green compaction: Warm compaction is selected, zinc stearate and polyvinyl alcohol are selected as lubricants, the compaction temperature is 20, 60, 80, 100, 120, 140 and 160 °C, and the compaction pressure is 320kN.

Calculation of theoretical density of compacts. The density of 45 steel is 0=7.8 g/cm², the density of WC is P2=15.8gem3, the mass fraction of WC particles and 45 steel matrix in the green compact is 50%, and the content of lubricant is neglected, the theoretical density of the green compact is approximate for p= 2910/(P+2)= 10.4 g/cm3The measurement of green compact density.

The pressed billet is trimmed to make a regular cylinder, and then the diameter and height of the bottom surface of the cylinder are measured with a micrometer, and the quality of the trimmed green compact is measured on an electronic balance, and the pressure is calculated. density of the blank.

(3) Vacuum sintering: vacuum sintering the pressed billet in a furnace to make a ceramic particle reinforced metal matrix composite material. The sintering temperature is 1350℃, and the vacuum degree of the sintering furnace is kept in the range of less than 5Pa.

(4) Post-heat treatment: the sintered composite material is kept at 800 °C for 1 h and then oil quenched.

Equipment selection: The RVS vacuum sintering furnace provided by SIMUWU is an excellent product for processing this kind of process. It has the characteristics of good temperature uniformity and high temperature control accuracy. SIMUWU provides a professional team of engineers who can solve various problems encountered in the production process and are committed to giving customers the most convenient and efficient experience.