Thermal expansion coefficients in Invar processed by selective laser melting

• DOI: 10.1007/s10853-017-1169-4
• Publication Date: 2017-05-11T16:25:26Z
• Authors: Neil J. Harrison; Iain Todd; Kamran Mumtaz
• Keywords: Invar; Selective Laser Melting; Negative Thermal Expansion

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.