Physical and chemical characterization methods for metal powders used for additive manufacturing processes
Porkka, Juuli (2016-10-20)
Physical and chemical characterization methods for metal powders used for additive manufacturing processes
Porkka, Juuli
(20.10.2016)
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Turun yliopisto
Kuvaus
Siirretty Doriasta
Tiivistelmä
Direct metal laser sintering (DMLS) is an additive manufacturing (AM) process in which metal powder is melted using laser beam to create solid parts. Melting is done by selectively scanning the cross-sections of the part one powder layer at a time. The properties of the final part depend on the powder characteristics which have a major influence on the processability of the powder. Optimization of powder characteristics ensures products that have good quality and consistency.
In this study properties of EOS CobaltChrome SP2, EOS MaragingSteel MS1 and EOS StainlessSteel 316L powders were characterized. Two different powders from each material were studied to determine the differences in their powder characteristics affecting either the laser sintering process or the quality of the final product. Most of the characterization methods were standard procedures according to ASTM F3049 – 14 but some additional methods were utilized. Standard test methods used were sampling (ASTM B215 – 15), size determination (ASTM B214 – 07 & ASTM B822 – 10), morphology characterization, chemical composition, flow characteristics (ASTM B213 – 13 & ASTM B964 – 09) and density (B212 – 13, B417 – 13 & B527 – 06). Additionally water content of powders was analyzed.
Most remarkable differences in the characteristics of the comparable powders were found in particle size distribution (PSD) and particle morphology. There were no significant differences in the elemental compositions of comparable powders observed.
Favorable powder characteristics were wide PSD and spherical and round particle shape especially in large particle size. Unfavorable characteristics were narrow PSD, irregular particle shape, agglomerates, excessive amount of fine particles and lack of fine particles. Wide PSD and high sphericity and roundness of particles improve compactibility and flowability of the powder. On the contrary narrow PSD, irregular particle shape and agglomerates reduce compactibility and flowability. Also excessive amount of fine particles has reducing effect on flowability.
Compactibility and flowability have an impact on the powder performance in the laser sintering process. Good flowability enables formation of uniform powder layers and high compactibility improves the density of the powder bed which yet increases the density of the solid part.
In this study properties of EOS CobaltChrome SP2, EOS MaragingSteel MS1 and EOS StainlessSteel 316L powders were characterized. Two different powders from each material were studied to determine the differences in their powder characteristics affecting either the laser sintering process or the quality of the final product. Most of the characterization methods were standard procedures according to ASTM F3049 – 14 but some additional methods were utilized. Standard test methods used were sampling (ASTM B215 – 15), size determination (ASTM B214 – 07 & ASTM B822 – 10), morphology characterization, chemical composition, flow characteristics (ASTM B213 – 13 & ASTM B964 – 09) and density (B212 – 13, B417 – 13 & B527 – 06). Additionally water content of powders was analyzed.
Most remarkable differences in the characteristics of the comparable powders were found in particle size distribution (PSD) and particle morphology. There were no significant differences in the elemental compositions of comparable powders observed.
Favorable powder characteristics were wide PSD and spherical and round particle shape especially in large particle size. Unfavorable characteristics were narrow PSD, irregular particle shape, agglomerates, excessive amount of fine particles and lack of fine particles. Wide PSD and high sphericity and roundness of particles improve compactibility and flowability of the powder. On the contrary narrow PSD, irregular particle shape and agglomerates reduce compactibility and flowability. Also excessive amount of fine particles has reducing effect on flowability.
Compactibility and flowability have an impact on the powder performance in the laser sintering process. Good flowability enables formation of uniform powder layers and high compactibility improves the density of the powder bed which yet increases the density of the solid part.