Additive manufacturing: improving the quality of AM processes through SEM analysis

By Antonis Nanakoudis - May 17, 2018

In a previous blog, we introduced Additive Manufacturing (AM) as a new manufacturing approach and described its key points (you can read the blog here). Additive Manufacturing, also known as 3D printing or rapid prototyping, has attracted the attention of many people and industries around the world due to its unlimited and promising potential. In this blog we will describe how the use of a Scanning Electron Microscope (SEM) can be a powerful tool to monitor and improve the quality of additive manufacturing processes.


SEM for detecting surface defects

SEM is currently used by AM operators as a characterization technique for finished products. Thanks to the high spatial resolution that a SEM offers, the surface quality of the components that are produced using AM processes can be carefully inspected. The use of SEM can assist in revealing possible (micro)structural surface defects which can compromise the mechanical properties and durability of the finished products.

For certain materials, such as titanium alloys, it has proven to be very challenging to manufacture dense components with the same properties as the components produced using conventional manufacturing processes. For this reason, SEM has proven to be a very useful characterization technique for finished products.
 

SEM on other additive manufacturing powder

However, SEM does not just assist in the inspection of the finished product; it can also be beneficial in the characterization of the raw material that is used in AM processes. Additive manufacturing is mainly a powder-based technique; such processes include sintering of a wide spectrum of powders. A wide variety of materials, mainly metals and alloys, plastics, ceramics, and composites, are used to build up components by CAD-operated process.

If we focus more on the metal powders that are being used, we will see that many metals are currently being used in additive manufacturing processes. Stainless steel, cobalt, nickel, titanium, aluminum, iron and
copper-based alloys have been used, but this list is growing all the time.

People who apply AM processes are interested in many different characteristics of the metal powders. Size (in the range of 1 to few hundreds of um) is a very important particle property to ensure uniform distribution, which will influence the product’s properties and its potential application. Shape (spherical particles are preferred) to enable efficient packing, flow and coating ability. And porosity, which influences the mechanical strength of the finished material and of course the chemical composition.

In most cases, careful inspection of the aforementioned properties of the powder is required and high homogeneity of their distribution is needed.

SEM and particle characterization

As mentioned above, SEMs are being used to image and characterize the surface of the products made by AM processes. Additionally, for the characterization of the powder material, specialized software can be used, such as the ParticleMetric software that has been developed by Phenom-World.

This software can automatically detect the particles that exist on a SEM sample and accurately characterize them by measuring several of the most important physical properties, such as size, shape, circularity, aspect ratio etc. It is of utmost importance that these characterization processes can be performed automatically due to the huge number of particles that need to be checked and analyzed.

Also, the use of a SEM allows for the chemical characterization of the powder material by using energy-dispersive X-ray spectroscopy (EDX)which most modern SEMs are equipped with (you can read more about the EDX technique here). By using an EDX detector in the SEM tool for AM processes, operators can accurately detect and quantify which elements exist in their sample.

image1-17
 
Figure 1: Screenshot of the ParticleMetric software. On the left, the detected particles in the SEM are shown. On the right, the results of the process are displayed; the detected particles, their properties and generated graphs with the particles' properties.

Therefore, it is obvious that a SEM can fully cover the characterization requirements of products and materials used for AM processes; with SEM imaging to inspect the surface of the finished product, specialized particle-analysis software to measure the physical properties of the powder material, and the EDX technique to detect and quantify the elements that they are composed of.

Additive manufacturing & SEM

In additive manufacturing, the quality control of the finished product — and detecting possible surface defects — is of utmost importance. However, as an additive manufacturer you want it to improve your AM processes without taking up too much time.

Additive Industries, the world’s first dedicated equipment manufacturer for industrial metal additive manufacturing systems, faced the same challenges. They managed to solve this obstacle and improve their quality control with scanning electron microscopy.

Schermafbeelding 2018-05-22 om 08.50.34


In this interesting video, Sandra Poelsma, Process Engineer, explains how Additive Industries quantifies the morphology, chemical composition and particle size distribution of metal powders with a desktop SEM. Watch the video here:

Watch AM & SEM in action

 


About the author

Antonis Nanakoudis is Application Engineer at Thermo Fisher Scientific, the world leader in serving science. Antonis is extremely motivated by the capabilities of the Phenom desktop SEM on various applications and is constantly looking to explore the opportunities that it offers for innovative characterization methods.

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