Effect of geometry and green density on the anisotropic sintering shrinkage of axisymmetric iron parts

ABSTRACT

Sintering shrinkage of prior cold compacted iron rings with different geometry (height to wall thickness ratio) and green density in the 6.5–7.3 g/cm³ range was investigated. It displays a minimum at an intermediate green density. Axial, tangential and radial shrinkages are different, due to the gradients of green density along the axial and the radial directions. Therefore, the effect of height on shrinkage and its anisotropy is the result of their effect on the stress distribution in the green parts during cold compaction, and the resulting green density and deformation experienced by the powder. Anisotropy decreases on increasing shrinkage.

KEYWORDS:

• Shrinkage anisotropy
• green density
• geometry

Disclosure statement

No potential conflict of interest was reported by the authors.

Notes on contributors

Alberto Molinari received the Ph.D. degree in Metallurgical Engineering in 1986 from Torino technical University, Italy. He is currently a full professor of the Department of Industrial Engineering, Trento University. His main research activity is devoted to the study of mechanisms of cold compaction and of sintering of metallic powders, to mechanical and wear properties of sintered steels, to the application of AM in medical industry. He received Honor Ph.D. by University Carlos III, Madrid in 2016 and is Fellow of EPMA and of APMI.

Sasan Amirabdollahian received MSc in Materials Science and Engineering in 2014 from University of Trento and is currently research assistant at the Department of Industrial Engineering, Trento University.

Marco Zago received the MSc in Materials and Industrial Production Engineering in 2016 from University of Trento and is currently PhD student at the Department of Industrial Engineering, Trento University.

Mats Larsson received the MSc in Mechanical Engineering in 1987 from the Faculty of Engineering at Lund University. He is Manager of Compaction and Sintering Development at Höganäs AB, Sweden.

Ilaria Cristofolini received the Ph.D. degree in Metallurgical Engineering in 1995 from Padua University, Italy. She is currently associate professor of the Department of Industrial Engineering, Trento University, in the field Design methods for industrial engineering. Her main research activity is devoted to the study of design methods for powder metallurgy, to design methods against wear, to PM parts geometric dimensioning and tolerancing.