Segregation measurement of powder injection molding feedstock using thermogravimetric analysis, pycnometer density and differential scanning calorimetry techniques

In this study, three measurement techniques were experimentally compared to quantify the effects of segregation on powder injection molding feedstock. In a powder metallurgy process, particle or phase segregation generates a fluctuation of the particle distribution in powder-binder mixture from point-to-point. Such demixing occurs generally before or during the injection process and can lead to the formation of defects such as cracks, distortions or heterogeneous shrinkage of the sintered parts. Thermogravimetric analysis, pycnometer density and differential scanning calorimetry were used to measure respectively the mass loss after binder burnout, the density and the enthalpy of fusion on several feedstocks with different solid loadings. It was demonstrated that the variation in solid loading can be measured with a sensitivity of at least +/- 0.5 vol.% of powder using the TGA and PD techniques only. It was also shown that the thermogravimetric analysis and the pycnometer density results are independent of feedstock formulation and can be obtained without the use of a calibration curve. The thermogravimetric analysis and the pycnometer density measurement are complementary and well-adapted experimental methods to measure the effects of segregation on powder injection molded green components. (C) 2015 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.