Sintering of metal powder samples with millimeter wave technology

Although the microwave effects on metal powder sintering are not fully understood, there have been no experimental investigations published yet about the change of penetration depth of microwave energy into a metal powder compact during sintering. At the Forschungszentrum Karlsruhe, Germany experimental investigations on sintering of Cu-powder compacts in nitrogen atmosphere have been performed in a compact gyrotron system operating at 30 GHz with a maximum power level of 15 kW. The samples were millimeter-wave (mm-wave) sintered in a dilatometer set-up, which allows in situ measurement of the linear shrinkage of the powder compact during the sintering process. This information can be used to optimise the process parameters as well. In parallel, measurements of temperature gradients within the powder compacts by use of two shielded type S thermocouples allow to distinguish between volumetric heating and surface heating. At low sample density and temperature volumetric heating has been observed.