Millimetre wave effects on sintering behaviour of metal powder compacts

Abstract Experimental investigations on millimetre wave sintering of copper and mixed elemental metal powder compacts in the system iron–copper–carbon have been performed in nitrogen atmosphere. Therefore, a compact gyrotron system operating at a frequency of 30 GHz and with a maximum power level of 15 kW was used. With metal powder compacts of different green densities, the temperature gradients within the powder metal compacts were measured during sintering using two shielded K type thermocouples. By this means, for the first time objective evidence for millimetre wave volumetric heating in powder metal compacts could be provided. With samples of low green density and at temperatures below ∼400°C, which means before the active stage of sintering starts, volumetric heating was found. Dilatometer measurements, microstructure analysis and mechanical testing supported these results.