Can Appropriate Thermal Post-Treatment Make Defect Content in as-Built Electron Beam Additively Manufactured Alloy...

Area of Science:

• Materials Science
• Additive Manufacturing
• Metallurgy

Background:

• Electron Beam Melting (EBM) is increasingly used for complex parts.
• Superalloys like Alloy 718 require post-treatments for optimal performance.
• Common post-treatments include Hot Isostatic Pressing (HIPing) and heat treatments.

Purpose of the Study:

• To investigate if post-treatments can negate the impact of as-built defects in EBM Alloy 718.
• To assess the effectiveness of HIPing and subsequent heat treatments on defect reduction and property attainment.

Main Methods:

• EBM of Alloy 718 samples with intentionally high defect content.
• Application of Hot Isostatic Pressing (HIPing) to reduce porosity.
• Solutionizing and aging heat treatments to achieve desired phase constitution.

Main Results:

• HIPing reduced defect content from 17% to below 0.3%, with remaining defects primarily oxide inclusions.
• Subsequent heat treatments resulted in nearly identical phase distribution and hardness regardless of initial defect levels.
• The study demonstrates the robustness of post-treatments against initial EBM process variations.

Conclusions:

• Post-treatments, specifically HIPing followed by solutionizing and aging, render initial defect content in EBM Alloy 718 inconsequential.
• This finding can reduce process optimization complexity and potentially increase production speeds for EBM.
• It supports the industrialization of EBM for demanding applications requiring Alloy 718 with stringent quality standards.