Microstructural Characterization and Mechanical Properties of L-PBF Processed 316 L at Cryogenic Temperature

Area of Science:

• Materials Science
• Additive Manufacturing
• Cryogenic Engineering

Background:

• Laser powder bed fusion (L-PBF) enables complex, lightweight part fabrication for aerospace and medical fields.
• Austenitic stainless steel 316 L offers excellent mechanical properties and corrosion resistance across temperatures.
• Understanding L-PBF 316 L performance at cryogenic temperatures is crucial for aerospace applications.

Purpose of the Study:

• Investigate the suitability of L-PBF 316 L for aerospace applications at cryogenic temperatures.
• Compare the behavior of L-PBF 316 L at -196 °C versus room temperature.
• Analyze microstructural changes and mechanical properties at cryogenic conditions.

Main Methods:

• Tensile testing at room temperature and -196 °C.
• Microstructure and fracture surface characterization via scanning electron microscopy (SEM).
• Phase analysis using X-ray diffraction (XRD) and nanoindentation.

Main Results:

• A significant increase in the strength of L-PBF 316 L was observed at -196 °C.
• Ductility remained at an acceptable level despite the strength enhancement.
• Formation of ε and α martensite phases at -196 °C correlated with increased strength.
• Nanoindentation revealed varying hardness in austenite, strained austenite, and martensitic phases (α, ε).

Conclusions:

• L-PBF 316 L exhibits enhanced strength at cryogenic temperatures due to martensitic transformations.
• The material retains sufficient ductility for aerospace use under cryogenic conditions.
• Microstructural analysis confirms the role of austenite-to-martensite phase changes in mechanical property enhancement.