Thermochemical and microstructural study of CaSO4 bonded investment as a function of the burnout process parameters

By means of the combined use of different analytical techniques, the chemical-physical properties of gypsum bonded investment are studied as a function of some burnout parameters such as temperature, atmosphere and thermal treatment time. The attention has been focused on the measurement of the temperature of the CaSO4 thermal decomposition that is strictly related to the origin of gas porosity and on gaining further insight on the microchemical and microstructural structure of the thermal treated CaSO4 bonded investment. The results evidence that the decomposition temperature, that is about 1000°C for an investment prepared and fired according to the producers directions, can be increased by varying the procedures, the duration and the temperature of the burnout cycle.