Oxidation-Assisted Cracking at 650 °C in Superalloy 718 Manufactured by Laser Beam Melting: Effect of Temperature and Strain Rate

Additive manufacturingAdditive manufacturing of complex parts in superalloy 718Superalloy 718 by Laser Beam MeltingMelting (LBM, also referred to Selective Laser MeltingSelective laser melting, SLMSLM) is currently under the evaluation by the aerospace industry, due to the opportunity to combine alloy 718Alloy 718 excellent properties and versatility of use, with the benefits and increasing maturity of LBM technology. In this work, the interactions between fractureFracture modes and deformation modes for LBM-manufactured 718718 were studied at 20, 450 and 650 °C. Vertical and horizontal tensile specimens were fabricated, then heat-treated with two sets of standard solution-agingAging treatments, before being tested in air over a range of strain rateStrain rate from 8 × 10–5 to 3 × 10−2 s−1. Results of these tests showed evidence of a coupling effect between oxidationOxidation and mechanical loading, resulting in oxidationOxidation-assisted crackingCracking of LBM 718718 alloy for the same temperatureTemperature and strain rateStrain rate conditions than conventionally-manufactured alloy 718Alloy 718. Also, in spite of consisting of fundamentally different microstructuresMicrostructures, relationships between fractureFracture modes and deformation modes for laser beam melted 718718 were found to be surprisingly consistent with the ones previously established for conventional 718718. These results suggests that microstructureMicrostructure parameters such as grain sizeGrain size and morphology, or phase distribution are not involved at the first order in the mechanisms controlling these interactions. To further describe these phenomena, the interactions between solute elements, mobile dislocations and interfaces must be considered.