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Ilaria Cristofolini,Nicolò Corsentino,Alberto Molinari,Mats Larsson 한국정밀공학회 2014 International Journal of Precision Engineering and Vol. No.
In the conventional press and sinter process, dimensional change on sintering determines the precision of the final parts, providingthat a good dimensional precision of green parts is ensured. Anisotropic dimensional change on sintering may be detrimental to theprecision of Powder Metallurgy (PM) parts, and it should be considered in the design step. The effect of material and geometry onthe 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 andcorrelated to the material and geometry. The effect of neglecting anisotropy in the design step was investigated, in terms ofdimensional tolerances, which can be obtained with different process capabilities. A model to describe the effect of material andgeometry on the anisotropic dimensional change is also being developed.
Ilaria Cristofolini,Melania Pilla,Andrea Rao,Stefano Libardi,Alberto Molinari 한국정밀공학회 2013 International Journal of Precision Engineering and Vol. No.
The effect of the sintering and sinter-hardening temperature on the dimensional and geometrical precision of ring-shaped parts was investigated. The parts were produced with a 3%Cr-0.5%Mo-0.5%C steel, compacted to 6.8 g/cm3 and sinter/sinter-hardened at 1250oC, 1300oC and 1350oC. The increase in the sintering temperature enhances the fraction of load bearing section and leads to an expected significant improvement of mechanical properties. Dimensional shrinkage increases with the sintering temperature,however, the dimensional and geometrical precision obtained in all the cases is very good even at very high sintering temperature. Dimensional variations are anisotropic, and the effect of anisotropy was estimated by evaluating the lack of precision attained when green parts are designed assuming an isotropic behavior.