Investigation of Additive Friction Stir Deposition of Inconel 718: Mechanical Performance and Microstructural...

Area of Science:

• Materials Science
• Additive Manufacturing
• Metallurgy

Background:

• Inconel 718 (IN718) is critical for aerospace and energy due to its high reliability.
• Additive friction stir deposition (AFSD) is a solid-state process producing defect-free metallic parts.
• Evaluating AFSD's impact on IN718 is vital for advanced applications.

Purpose of the Study:

• To investigate the effects of AFSD on the microstructure and mechanical properties of IN718.
• To compare as-deposited IN718 with its feedstock material.
• To understand the anisotropy introduced by the AFSD process.

Main Methods:

• Additive friction stir deposition (AFSD) was used to process IN718.
• Tensile testing was performed in both traverse and build directions.
• Microhardness testing, X-ray diffraction (XRD), and elemental mapping were employed.

Main Results:

• Ultimate tensile strength (UTS) increased by 5% in the traverse direction, but elongation decreased.
• Build-direction specimens showed lower UTS and significantly reduced elongation, indicating anisotropy.
• Microhardness increased by 20% due to grain refinement from 11 µm to 3 µm.
• XRD detected no secondary phases; oxygen-enriched regions were found at interlayer boundaries.

Conclusions:

• AFSD refines IN718 microstructure, increasing hardness and traverse-direction strength.
• The process induces significant mechanical anisotropy, particularly reduced ductility in the build direction.
• Grain refinement is a key factor in improved hardness and strength, while interlayer chemistry may affect ductility.