Influence of atmosphere impurities on debinding, outgassing and sintering of hardmetals

Atmosphere impurities during sintering influence the thermal behavior of hardmetals during the heat treatment. Consequently also the final properties of these materials are affected. Special impurities are humidity and oxygen. Carbon dioxide, carbon monoxide, hydrogen or methane can also be part of the atmosphere and may affect processes during sintering. Methods of thermal analysis (Thermodilatometry, Thermogravimetry - Mass Spectrometry and Differential Scanning Calorimetry) were used for characterization of the thermal behavior of a hardmetal mixture as a probe for controlling the production processes. The debinding, outgassing, sintering and melting of the metal binder phase were examined. The investigations were focused on the interactions between gas phase and hardmetal mixture in dependence on humidity of the furnace atmosphere. The influence of the water content of the gas phase was proven by Thermogravimetry - Mass Spectrometry: gas reactions are changed regarding to temperature ranges and mechanisms (sequence of reaction steps). The achieved process knowledge enables hardmetal producers to improve quality and to reduce scrap.