A B S T R A C TThe oxidation behaviour of IN 718 alloys produced by laser beam melting and electron beam melting was compared to that of the wrought alloy at 850°C in laboratory air. Oxide scales of all alloys were similar in nature and morphology with small differences due to powder particles sintered on the surface of additive manufacturing parts. Nevertheless, major differences in surface topography were noticed, these could affect surface area estimations and consequentlymass gain estimations. A quantitative correlation was determined between apparent parabolic rate constant and surface area.

The intergranular oxidation in air at 850°C of alloy 718 produced by laser beam melting and electron beam melting was compared to that of the wrought alloy. Quantitative analyses revealed that the amount of grain boundary oxidation was similar for these alloys. However, the additively manufactured ones presented deeper and thicker oxides at grain boundaries, due to grain size heterogeneity and to a smaller number of special boundaries. Results show that intergranular oxidation kinetics follows Wagner's theory on internal oxidation considering not only O diffusion at the intergranular oxide/metal interfaces but also Al and Ti diffusion in the bulk.

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Extending the fused filament fabrication process to highly filled thermoplastics in metallic powder used in metal injection molding is a promising method to produce small series. However, the lack of adhesion between deposited filaments can cause ruptures during the fabrication or debinding process. We designed a simple device to measure the shear strength required to tear off a filament deposited on a substrate. This device makes it possible to quickly determine the processing window for a good welding of filaments. We developed a 2D thermal simulation using the finite difference method while integrating the enthalpy of fusion and crystallization kinetics of the material. We then fitted it to the thermal measurements at depths of 0.45 and 0.75 mm under the substrate surface using small‐diameter thermocouples. Simulation results highlight the key role of the thermal contact resistance between the filament and the substrate in the evolution of the interface temperature. This provides essential information to explain the process window that can be determined experimentally. The characteristic time of macromolecule diffusion was determined by rheological measurements and was found to be too small to play a role in filament bonding for the simulated cooling rates for the studied material. The methodology introduced in this work was used to improve highly filled polymers interlayer adhesion, but it can be used to improve other filled or unfilled polymers.

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