Processes during the Heat Treatment (Sintering) of WC-Co Compacts

During the sintering of WC-Co powder compacts reactions occur which determine the properties of the final product. A better understanding of these processes allows the optimisation of the materials and their production. Therefore the following processes are discussed: (1) desorption or vaporisation (and cracking respectively) of air, water, residues of milling liquids and lubricants (2) melting of lubricants and WC-Co eutectics (3) reduction of oxidic impurities (4) magnetic transformation of the Co binder phase and (5) mass transport phenomena during sintering. These reactions result in length changes, mass changes, thermal effects and gas formation. They are characterised by means of thermoanalytical methods (Thermodilatometry, Thermogravimetry, Differential Scanning Calorimetry, and Mass Spectrometry). With kinetic analysis it is possible to obtain information about the specific mechanisms, predict the thermal behaviour and optimise the time-temperature-atmosphere profiles.