Thermal expansion coefficients in Invar processed by selective laser melting

Neil J Harrison; Iain Todd; Kamran Mumtaz

doi:10.1007/s10853-017-1169-4

Thermal expansion coefficients in Invar processed by selective laser melting

J Mater Sci. 2017;52(17):10517-10525. doi: 10.1007/s10853-017-1169-4. Epub 2017 May 11.

Authors

Neil J Harrison¹, Iain Todd², Kamran Mumtaz¹

Affiliations

¹ 1Department of Mechanical Engineering, University of Sheffield, Sheffield, UK.
² 2Department of Materials Science and Engineering, University of Sheffield, Sheffield, UK.

Abstract

This work investigates whether the unique low thermal expansion property of Invar (64Fe-36Ni) is retained after processing using the additive manufacturing process selective laser melting (SLM). Using this process, near-full-density components (99.96%) were formed by melting thin (20 μm) layers of powdered Invar (15-45 μm particle size). The mechanical properties of SLM Invar were comparable to that of cold-drawn Invar36^®; however, the thermal coefficient of expansion was observed to be a lower value and negative up until 100 °C. This negative value was attributed to residual stress in the as-deposited parts. The low thermal expansion property of Invar was still maintained when processed using a non-conventional layer-based additive manufacturing technique.