A Study on Internal Defects of PREP Metallic Powders by Using X-ray Computed Tomography

Area of Science:

• Materials Science
• Powder Metallurgy
• Additive Manufacturing

Background:

• The plasma rotating electrode process (PREP) is crucial for producing high-quality metal powders.
• Understanding and controlling internal defects in PREP powders is essential for downstream applications, particularly in additive manufacturing.
• Ti-6Al-4V, 316-steel, and Co-29Cr-6Mo alloys are widely used in demanding industries.

Purpose of the Study:

• To characterize the distribution, proportion, and nature of internal defects in PREP-produced powders of Ti-6Al-4V, 316-steel, and Co-29Cr-6Mo alloys.
• To investigate the influence of PREP rotation speed and powder particle size on internal defect formation.
• To determine the effect of alloy composition on the occurrence of internal defects.

Main Methods:

• Powder samples of Ti-6Al-4V, 316-steel, and Co-29Cr-6Mo were produced using the plasma rotating electrode process (PREP) at varying rotation speeds.
• Scanning electron microscopy (SEM) was employed to examine the surface morphology and microstructural features of the powders.
• Synchrotron X-ray computed tomography (CT) was utilized for non-destructive characterization of internal defects within individual powder particles.

Main Results:

• Internal pores were observed to form more readily in coarser powder particles compared to finer ones within the same alloy.
• Increasing the rotation speed during the PREP significantly reduced the proportion of powder particles containing internal pores.
• The intrinsic composition of the alloy demonstrated a considerable impact on the propensity for internal defect formation.

Conclusions:

• Particle size and PREP rotation speed are critical process parameters influencing internal pore formation in metal powders.
• Alloy composition plays a significant role in the defect characteristics, suggesting tailored process control is necessary for different materials.
• Optimizing PREP parameters based on alloy type and desired particle size distribution can minimize internal defects, leading to improved powder quality for applications like additive manufacturing.