Mechanical and functional properties of Invar alloy for μ-MIM

Abstract

Micrometal injection moulding (μ-MIM) is a promising alternative for fabricating micro parts. Low coefficient of thermal expansion Fe_x–Ni_1−x alloys are suitable to meet high dimensional stability with temperature keeping acceptable mechanical properties. However, these alloys are sensible of elements contamination during the debinding and sintering stages, and their dimensional stability and mechanical properties could be affected. The present work studies the effect of using combinations of debinding and sintering atmospheres in the micropowder injection moulding of Invar 36 feedstocks based on cellulose acetate butyrate binders. Microtensile specimens were successfully injected. Densification and microstructure at different conditions were linked with mechanical and physical properties of the parts. The processing conditions, and thus, the residual C, O and especially H influence severely these properties.

Keywords:

• Invar 36
• Cellulose acetate butyrate
• Polyethylene glycol
• Micro-MIM
• Sintering atmospheres

Acknowledgements

The authors wish to thank Guzmán Global S.L. and Mimtech Alfa for their collaboration on the ECOPIM project (reference no. IPT-2011-0931-20000) that was funded by the Spanish Ministry of the Economy and Competitiveness. Furthermore, the authors would like to acknowledge the funding provided by CAM-Consejeria de Educación Dir. Gral. Universidades e Investigación in the project ESTRUMAT (reference no. S2009/MAT-1585) and the Nacional Project (grant no. MAT2012/38650-C02-01).