Characterization of the porosity and pore behavior during the sintering process of 420 stainless steel samples produced with gas- and water-atomized powder using powder based 3-d printing

摘要

A series of 420 stainless steel samples produced using the M-flex system (a powder-based 3D printer) were used to study the systematic evolution of the changes in porosity and pore size behavior after sintering. Powders produced from gas atomization and water atomization have been used to prepare green coupons. The major goals of this work were to; 1)study the optimum sintering processing parameters in terms of temperature and holding time to access the level of densification, 2)develop a better understanding of the relationship between powder characteristics, density, porosity and sintering parameters, 3)investigate the sintering behavior of powders of the same chemical composition but different particle size and distribution.udThe microstructural characterization for both gas- and water-atomized powder has been done with the aid of a Scanning Electron Microscope (SEM) and fractal dimension analysis. Different sintering conditions, i.e. temperature and holding time, were examined. The coupon samples were encapsulated in a vacuum quartz tube to avoid oxidation. Shrinkage is measured after sintering, based on which density and porosity are calculated for each sample. Optical Microscope (OM) has been used to observe the microstructure change in the central part of each sample.udThe powder characterization results point out that water atomized powder has a more irregular and complex shape compared to gas atomized powder. Thus it is predicted to have better sintering behavior. The sintering results show that water atomized powder is easier to sinter and can get lower porosity at the same sintering condition compared to the gas atomized powder. However, full densification was not observed under the experimental conditions used in this study. Thus, future studies need to be conducted.