Impact of Notches on Additively Manufactured Inconel 718 Tensile Performance

Area of Science:

• Materials Science
• Mechanical Engineering
• Additive Manufacturing

Background:

• Inconel 718 is a high-performance alloy widely used in demanding applications.
• Additive manufacturing (AM), specifically laser powder bed fusion (L-PBF), offers advantages in creating complex geometries.
• Understanding the mechanical behavior of AM materials, including notch sensitivity, is crucial for reliable design.

Purpose of the Study:

• To characterize the notch sensitivity of additively manufactured Inconel 718 produced by L-PBF.
• To evaluate the effect of different notch geometries and build orientations on tensile properties.
• To compare experimental strain measurements with finite element analysis (FEA) predictions.

Main Methods:

• V-notched and smooth tensile test specimens of L-PBF Inconel 718 were fabricated in vertical and horizontal orientations.
• Tensile testing was performed, measuring both total axial strain and localized notch diametral strain.
• Finite element analysis (FEA) was conducted to validate strain measurements.
• Fractography analysis was performed on fracture surfaces.

Main Results:

• Notched specimens exhibited higher tensile strength compared to smooth specimens, resulting in a notch-sensitivity ratio (NSR) greater than one.
• The material demonstrated notch strengthening, attributed to increased triaxial stress and material constraint at the notch tip.
• A ductile failure mode was observed in all specimens, with reduced ductility noted for smaller notch root radii.

Conclusions:

• L-PBF Inconel 718 is a notch-strengthened material under tensile loading conditions.
• The study provides initial data on notch effects in AM Inconel 718, highlighting the influence of notch geometry and build orientation.
• Further research is recommended to investigate notch effects under fatigue and stress-rupture loading.