Metallic powders: from rheology to the performance of engineered materials
Complementary to traditional manufacturing procedures based on the removal of matter, additive manufacturing makes it possible today to achieve an unbeatable level of freedom during the designing process and exceptional implementation time. This technique is used in many applications, in very demanding fields such as aeronautics, medicine, space, defense…
Additive manufacturing consists of assembling a part by piling up successive layers of powder (mostly metallic powder), melted using a beam (either a laser or a beam of electrons).
This process is sensitive to changes in particle sizes and shapes in the powder being used. These geometrical characteristics impact the spread and compactivity of the material during the manufacturing process.
To ensure a certain level of quality for printed parts, metallic powders need to meet various requirements to be able to perform as intended. Integrated into the French NF E67-010 standard, specifying the technical requirements for metallic powders designated for use in additive manufacturing, the main parameters are:
- Particle Size Distribution usually measured with a laser granulometer in accordance with the ISO 13320 standard making it possible to determine conventional parameters such as D10, D50 and D90.
- Flowability characterized by the average time it takes a powder to flow through a calibrated Hall or Carney funnel in accordance with the ISO 4490/ASTM B213 and ASTM B964 standards respectively
- Bulk and tapped density are measured to characterize a powder’s capacity organize itself and purge trapped air. These tests are performed with a volumenometer inaw the ASTM B527 and ISO3953 standards. The Hausner ratio is the ratio of tapped density to bulk density.
- True density is measured with a pycnometer in accordance with the ISO 12154 or ASTM B923 standards. This value is used to determine theoretical density and the internal porosity of a powder
- Morphology is studied under a Scanning Electron Microscope (FESEM) and under an Optical Microscope to determine the granulomorphology, the sphericity and the agglomeration state of the powder
- Humidity, determined by gravimetry after a drying the sample in accordance with ASTM E1868
- Chemical composition of metallic powders, determined using spectroscopy techniques such as ICP-AES and ICP-MS or elemental techniques to quantify C, H, O, N, S elements.
Compliance with the requirements associated with these different characteristics allows metallic powders to achieve a low defect rate (porosity, inclusion, etc.) and a high level of compactness in the part being manufactured, which in turn results excellent mechanical properties
Analysis of metallic powders: why call on FILAB?
With extensive experience in implementing these different techniques, FILAB is able to assist you in analyzing your metallic powders and with our expertise of activities relating to additive manufacturing:
- Chemical composition analysis of metallic powders using ICP-AES, ICP-MS and/or using C/S, O/N, and H elemental analyzers
- Granulometric analysis using laser granulometry in accordance with the ISO 13320 standard
- BET specific surface area measurements
- Flowability testing in accordance with the ASTM B213, ISO 4490 and ASTM B964 standards
- Density measurements in accordance with the ASTM B527 and ISO 3953 standards
- SEM FEG EDX or Optical Microscope morphological analysis
- Approval from the SAFRAN Group, in accordance with the Ma0015 scope statement, for the characterization of metallic powders.
For more information, feel free to contact one of our experts via email at contact@filab.fr
