Discover how to optimize your metal powders with particle size and shape analysis
When you need an intricately designed part or component, such as a turbine blade for a jet engine or a medical implant, few techniques offer as much precision and control over the final product as additive manufacturing (AM). Its ability to create items with unique properties from digital files, on demand, is of great value in many industries.
One of the fastest-growing AM technologies is metal powder bed fusion (metal PBF), which enables the production of large parts with highly complex geometries. However, particle characterization of the metal powders used in this process is critical to ensure a flawless result. Read on to find out why – and the best tools for analyzing these powders.
Why does metal powder particle size and shape matter?
Particle size plays a direct role in many aspects of the metal PBF process. For example, smaller particles (<10 µm) have a higher surface-to-volume ratio, which increases interparticle friction and reduces flowability. Larger particles (>60 µm) flow more easily but don’t form dense powder beds, resulting in poor part density.
Fine powders also allow for thinner layers and finer print resolution, enabling the production of parts with more intricate details and smoother surface finishes. Coarser powders, on the other hand, require thicker layers, which can lead to more pronounced staircase effects on sloped surfaces.
A mixture of particle sizes is therefore best, providing a balance between flowability and packing density, with smaller particles filling the gaps left between larger powders. However, the blend must be closely controlled. For example, if there are too many large particles, more energy is required to melt the powder. And all of this must be achieved within a very narrow size distribution.
Particle shape is also important because it directly affects flowability and packing density. Spherical particles typically both flow more easily and pack more uniformly, enabling a consistently thick powder layer and high-quality parts. By contrast, irregularly shaped particles can cause an uneven powder layer, which reduces the laser’s efficiency and causes defects in the part produced. So, for strong, high-quality components, it’s just as important to optimize particle shape as size.
Laser diffraction: Fast, accurate particle size analysis
Laser diffraction is a widely used particle sizing technique for powders, liquids, and suspensions. It measures the angle and intensity of light scattered by particles as a laser beam passes through a sample. Particle size and distribution are then deduced using an appropriate optical model such as Mie theory or the Fraunhoffer approximation.
This particle sizing technique is particularly effective for metal powders because of its wide measurement range. In fact, metal powders for PBF are often in the 5-150 µm range, which is well within the capabilities of modern laser diffraction instruments.
Speed and efficiency are also key, especially in high-throughput production environments. Laser diffraction systems can even be integrated into the production line to provide real-time monitoring data. This allows operators to make immediate adjustments if powder characteristics deviate from specified limits.
Static image analysis: For both size and shape analysis
Of course, you’ll typically also need to analyze particle shape in metal PBF – which is where automated static image analysis comes in. This technique combines particle size measurements with assessments of shape properties such as circularity, convexity, elongation, and abrasiveness.
This allows operators to detect agglomerates, foreign particles, and other anomalous materials, as well as to cross-validate the particle sizing results they get from laser diffraction. Static image analysis can characterize both spherical and irregularly shaped particles, and can analyze tens to hundreds of thousands of particles per measurement, making it ideal for high-throughput environments.
Find the best instrument for your needs in our upcoming webinar!
Choosing the right instrument is an important step in improving your metal PBF processes. After all, different applications require different levels of throughput and precision. To help you make the best decision, we’re hosting a webinar on particle size and shape characterization on November 19 at 14:00 CET.
Our experts will discuss the importance of particle size and shape in the metal PBF process and show how the Mastersizer 3000+ leverages the power of laser diffraction to provide highly accurate particle size analysis. They will also demonstrate how static image analysis with the Morphologi 4 can be used to monitor particle shape and even predict process performance.
From nickel superalloys for turbine blades to stainless steel powders in medical devices, applications for particle size and shape analysis truly come in all shapes and sizes. So don’t miss this opportunity to get all your questions answered by the experts in laser diffraction and static image analysis!
If you’d like to learn more about particle sizing, sign up for the webinar today – it’s free to attend!