A Combined Experimental-Numerical Method to Evaluate Powder Thermal Properties in Laser Powder Bed Fusion

Area of Science:

• Materials Science
• Thermal Engineering
• Additive Manufacturing

Background:

• Powder bed metal additive manufacturing (AM) is a thermal process where heat conduction is key.
• Accurate prediction of process temperatures requires understanding powder thermal conductivity, which differs significantly from solid forms.
• Measuring powder thermal conductivity is experimentally challenging.

Purpose of the Study:

• To investigate and determine the powder thermal conductivity under powder bed conditions.
• To develop and validate a combined experimental and numerical approach for measuring thermal properties of powders.
• To provide crucial data for enhancing thermal models in metal additive manufacturing.

Main Methods:

• Utilized laser powder bed fusion (LPBF) to create disk-shaped samples containing powder.
• Employed laser flash analysis to measure thermal diffusivity and temperature history.
• Developed and validated a finite element (FE) model for transient heat transfer, incorporating an inverse method to determine powder thermal conductivity.

Main Results:

• The study successfully estimated the thermal conductivity of nickel alloy 625 powder.
• An improved FE model geometry enhanced the consideration of powder particle contact.
• The determined thermal conductivity was 1.01 W/m K at 500°C for the nickel alloy 625 powder.

Conclusions:

• The combined experimental and numerical method provides a viable approach for measuring powder thermal conductivity.
• Accurate thermal conductivity data is essential for precise thermal process modeling in AM.
• This research contributes valuable thermal property data for nickel alloy 625 in powder bed AM applications.