How to... get to grips with the Explorer 4 Additive

Materials World magazine
1 Jul 2018

Trisha Rice, Vice President and General Manager of materials science solutions at Thermo Fisher Scientific, talks about the company’s new analysing technology for additive manufacture. 

What is Thermo Fisher?

Thermo Fisher makes imaging and analysis systems, including scanning electron microscopes (SEMs), transmission electron microscopes (TEMs), DualBeam (combined focused ion beam/SEM) systems, and mass spectrometers. By combining our instruments with operational and analytical software, we guide customers from initial questions to robust, reproducible final answers, quickly and efficiently. Our ability to integrate chemical, physical, and elemental information over a broad range of spatial scales, analytical techniques, and sample types helps to define material properties and performance of composition and structure at the molecular and atomic scale. 

What is the Explorer 4 Additive?

The Thermo Scientific Explorer 4 Additive is our automated SEM with integrated energy dispersive X-ray (EDX) spectrometry specifically designed to measure particle size, shape, and composition in metal powders for additive manufacturing (AM). These powder particle characteristics can have a significant impact on powder bed formation, melt pools, and microscopic homogeneity. Excessive variations and unknown properties of the powder can lead to nonuniform layering, increased defects, poor surface finish, and potentially catastrophic failures. With a clear understanding of the powder characteristics, users can proceed confidently from the initial build through repeated recycling, knowing their powder is consistent in size and shape and free of contaminants. The Explorer 4 Additive also provides high-resolution imaging and analysis of finished parts for process improvement, defect and failure analysis, and outgoing quality assurance.

What are the benefits?

SEMs measure the entire range of particle sizes used in AM powders, from 200nm to several millimeters. SEM analysis therefore avoids having to make assumptions about particle shape and refractive index that can introduce errors in optical size measurements. Its measurements of maximum and minimum diameter, perimeter, and shape are taken directly from high-resolution images of the particles, avoiding preferred orientation effects and sizing bias and providing accurate characterisation of new or mixed materials. This can be especially important when evaluating recycled material, in which particle shape may differ from virgin powder. Analysis recipes are updated easily for new powders. Lastly, the Explorer 4 Additive calculates both particle volume and size distributions to provide a more holistic view of the powder.  

How does it characterise particle shape?

The Explorer 4 Additive automatically and simultaneously measures size and shape parameters, such as minimum and maximum diameter, perimeter, aspect ratio, roundness, and feret diameter, all of which can be displayed as a histogram with 10%, 50%, and 90% values (e.g. d10, d50, and d90). For production environments, built-in recipes will find deformed particles using pre-determined criteria, or the user can set their own pass-fail criteria based on the parameters of their choice. This automated process replaces user subjectivity with a reproducible quantitative approach, assuring consistency across batches and operators.

Can it analyse particle composition in a production setting?

SEM/EDX has long been the gold standard for identifying and analysing undesired particles, but, until now, it has been a time-consuming, manual process. The Explorer 4 Additive uses automated routines, developed in cooperation with AM customers, to identify impurities, acquire their basic characteristics, and log their locations. Using the integrated particle inspector function, the operator can relocate particles of interest for more detailed examination and create reports containing individual particle images, parameters, and composition. This program also provides an offline-tabulated view of every particle, freeing up the instrument for continued testing.

What capability does the system provide for inspection and analysis of finished parts?

It is a dual-purpose platform, functioning either as an imaging system or an automated particle analysis system. Equipped with both a secondary electron detector and a four-segment backscattered electron detector, it can be used as a traditional SEM to provide high-resolution imaging of grain structures and critical surface features of coatings. It identifies and characterises fractures, surface quality, inclusions, pores, and more. Its integrated EDS system can detect elements from boron to americium in the periodic table.

Is it easy to use in a production environment?

Yes, it was specifically designed for a production environment. Its user-friendly interface is easy for new operators to learn, but preserves the flexibility needed by expert users. Sophisticated automation permits continuous, unattended operation. It is fast, measuring up to 200 particles per minute and automatically generating one-click standard reports that include size and shape distributions and identify unexpected contaminant particles. It has integrated electromagnetic shielding and vibration isolation, and a plug-and-play design built to ensure fast installation and high up time.