Cyclic Oxidation Of Alloy 718 Produced By Additive Manufacturing Compared To A Wrought-718 Alloy

The cyclic oxidation resistance at 900 degrees C of the alloy 718 produced by laser beam melting and electron beam melting was compared to that of the wrought-718 alloy. Results showed large differences regarding the rate of oxide layer spallation. The wrought alloy presents much more adherent oxide scale. Moreover, the standard heat treatment and the surface grinding slightly delay the catastrophic spallation. The role of sulfur and manganese on the adhesion of the oxide scale is quantitatively discussed using thermodynamic modelling. This result may force restrictions on the chemical composition of the alloy 718 powder used for additive manufacturing.