An Improved Design Method for Net-shape Manufacturing in Powder Metallurgy

The effectiveness of powder metallurgy as net-shape/near net-shape manufacturing technology is determined by the possibility of obtaining complex parts matching the required narrow tolerances. Sintering process determines change in volume of the green, and the related dimensional changes are significantly anisotropic. Anisotropy is affected by several variables, such as material, compaction and sintering parameters, geometry, whose influence is difficult to be distinguished and determined. Anisotropic dimensional change on sintering has been investigated in depth using an experimental approach, relating measurements results to the mechanisms responsible for the phenomenon. Main results concerning the influence of different variables are briefly presented in this work. Such results served as the basis for the development and further improvement of a design method, aimed at predicting anisotropic dimensional change. Main steps of the design method are presented and an example of application to a real part is described. Strong agreement between predicted and real dimensional changes has been observed, and compared to the attainable dimensional tolerances.