Hydrothermal Hot Isostatic Pressing (HHIP)-Experimental Proof of Concept

Area of Science:

• Materials Science
• Additive Manufacturing
• Surface Engineering

Background:

• Additive manufacturing (AM) of aluminum alloys often results in micro-pores.
• Traditional hot isostatic pressing (HIP) requires high temperatures and inert gases, potentially altering microstructure.

Purpose of the Study:

• To introduce and validate a new hydrothermal hot isostatic pressing (HHIP) method for AM aluminum parts.
• To assess the efficacy of HHIP in reducing porosity and its impact on microstructure and mechanical properties.

Main Methods:

• Testing a novel HHIP approach using hydrothermal water conditions without inert gas on 3D-printed Al-10%Si-0.3%Mg parts.
• Applying HHIP at 300-350 MPa and 250-350 °C for 6-24 hours.
• Evaluating material loss, pore reduction, surface area reduction, and microstructural integrity.

Main Results:

• Achieved an 85.7% reduction in micro-pores and a 90.8% reduction in pore surface area at 350 °C.
• Minimal material loss (<0.5% w/w) due to corrosion.
• Preserved the as-received microstructure with significantly reduced porosity.

Conclusions:

• The gas-free HHIP method is a viable, lower-temperature alternative for post-processing AM aluminum parts.
• This technique promises improved mechanical properties without compromising fatigue resistance.
• The HHIP approach shows potential for broader application to other additively manufactured metal components.