Study of the Influence of Material and Geometry on the Anisotropy of Dimensional Change on Sintering of Powder Metallurgy Parts

In the conventional press and sinter process, dimensional change on sintering determines the precision of the final parts, providing that a good dimensional precision of green parts is ensured. Anisotropic dimensional change on sintering may be detrimental to the precision of Powder Metallurgy (PM) parts, and it should be considered in the design step. The effect of material and geometry on the anisotropic dimensional change is studied in this work. Four different iron alloys and five different geometries were considered. Dimensions were measured both on green and on sintered parts and the anisotropy of dimensional change was evaluated and correlated to the material and geometry. The effect of neglecting anisotropy in the design step was investigated, in terms of dimensional tolerances, which can be obtained with different process capabilities. A model to describe the effect of material and geometry on the anisotropic dimensional change is also being developed.