Thermal behaviour of cermets and hardmetals during debinding and sintering
Most important processes during heat treatment of powder mixtures for production of cermets and hardmetals are drying, dewaxing, outgassing, melting of the binder phase and sintering. Results of sintering experiments on the lab scale are presented and discussed. The experiments include sintering of materials with various compositions of hard phases (WC, TiCN) and metallic binder phases (Co, Ni). The multiphase reactions are investigated by methods of thermal analysis (Thermodilatometry, Differential Thermal Analysis, Thermogravimetry). Selected microstructures are inspected by high resolution field emission scanning electron microscopy. The influence of furnace atmosphere (cermets in helium or nitrogen and hardmetals in helium) and gas pressure on gas reactions are investigated by a thermobalance-mass spectrometer-system. For these studies an orifice coupling system for normal pressure in the thermobalance (1000 mbar) was modified in order to use this system also at a pressure range of approximately 0.1 to 10 mbar. The achieved process knowledge enables better understanding for sintering cermets and hardmetals and to improve both the processes and the material quality.