Thermal expansion coefficients in Invar processed by selective laser melting.

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.