ASTM F3606-22

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: F3606 − 22
Standard Guide for
Additive Manufacturing — Feedstock Materials — Testing
Moisture Content in Powder Feedstock
This standard is issued under the fixed designation F3606; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope D6869 Test Method for Coulometric and Volumetric Deter-
mination of Moisture in Plastics Using the Karl Fischer
1.1 This standard provides guidelines for measuring mois-
Reaction (the Reaction of Iodine with Water)
tureinpowderfeedstockusedinadditivemanufacturing(AM).
D7191 Test Method for Determination of Moisture in Plas-
It applies to metallic, ceramic, and polymer AM powder
tics by Relative Humidity Sensor
feedstocks.
E473 Terminology Relating to Thermal Analysis and Rhe-
1.2 This guide provides a description of test methods
ology
commonly used to measure moisture and references to their
E1131 Test Method for CompositionalAnalysis by Thermo-
associated standards.
gravimetry
E1142 Terminology Relating to Thermophysical Properties
1.3 This guide provides best practice guidance on how to
apply the test methods to make them suitable for AM powder E1409 Test Method for Determination of Oxygen and Nitro-
gen in Titanium and Titanium Alloys by Inert Gas Fusion
characterization.
E1868 Test Methods for Loss-On-Drying by Thermogravi-
1.4 This guide is suitable for measuring moisture in AM
metry
powder feedstock over the range of 10 µg⁄g to 10 000 µg⁄g.
2.2 ISO/ASTM Standard:
1.5 The values stated in SI units are to be regarded as
ISO/ASTM 52900 Additive manufacturing — General prin-
standard. No other units of measurement are included in this
ciples — Fundamentals and vocabulary
standard.
2.3 ISO Standards:
1.6 This standard does not purport to address all of the
ISO 17034 General requirements for the competence of
safety concerns, if any, associated with its use. It is the
reference material producers
responsibility of the user of this standard to establish appro-
ISO 3954 Powders for Powder Metallurgy Purposes —
priate safety, health, and environmental practices and deter-
Sampling
mine the applicability of regulatory limitations prior to use.
1.7 This international standard was developed in accor-
3. Terminology
dance with internationally recognized principles on standard-
3.1 Definitions—Powder metallurgy terms are defined in
ization established in the Decision on Principles for the
Terminology B243. Additive manufacturing (AM) terms can
Development of International Standards, Guides and Recom-
befoundinISO/ASTM52900.Technicaltermsinrelationwith
mendations issued by the World Trade Organization Technical
thermogravimetry(TGA)andlossondrying(LOD)aredefined
Barriers to Trade (TBT) Committee.
in Terminologies E473 and E1142, respectively. Relative
humidity sensor terminology is in accordance with Terminol-
2. Referenced Documents
ogy D7191, while terms related to the Karl Fischer method are
2.1 ASTM Standards:
described in Test Method D6869.
B215 Practices for Sampling Metal Powders
B243 Terminology of Powder Metallurgy
4. Summary of Guide
4.1 Different methods can be used to measure moisture in
This guide is under the jurisdiction of ASTM Committee F42 on Additive AM powders. For all methods of interest, the sample of
Manufacturing Technologies and is the direct responsibility of Subcommittee
powdersareheatedintheinstrumenttovaporizethewater.The
F42.01 on Test Methods.
amount of water is then evaluated using different approaches
Current edition approved Nov. 1, 2022. Published December 2022. DOI:
10.1520/F3606-22.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Available from International Organization for Standardization (ISO), ISO
Standards volume information, refer to the standard’s Document Summary page on Central Secretariat, Chemin de Blandonnet 8, CP 401, 1214 Vernier, Geneva,
the ASTM website. Switzerland, https://www.iso.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F3606 − 22
and procedures, depending on the method, as defined in the hydroxides. Thus, the amount of moisture may change with
referenced standards. In coulometric titration methods (for time even if the powder is stored in a tightly sealed container.
example, Karl Fisher as described in Test Method D6869) and Reaction of the powder with water may also happen during the
relative humidity sensor methods (as described in Test Method analysis as the powder is heated up. This reaction will reduce
D7191), a dry gas carries the volatiles (evaporated when the the amount of water available at the surface of the powder and
samples are heated up) into a titration cell (Karl Fischer) or may impact the results (that is, underestimate the amount of
humidity sensor (relative humidity sensor) to measure the water measured). If such reactions are expected to occur, their
amount of water. For gravimetric or loss-on-drying (LOD) impact on the measurements should be evaluated. This can be
methods (as described in Test Methods D6869, D7191, E1131, done using oxygen analysis to evaluate the amount of oxide
and E1868), the weight of the samples is measured during the formed with time or during a test.
test and the weight variation is converted into a water content
5.9 The amount of water adsorbed on the surface of a
assuming that water is the only compound evaporating from
powder depends on temperature and relative humidity and is
the sample during the test and there is no decomposition or
determined by moisture sorption isotherm (water content in
modification of the sample during the test. Presence of other
equilibrium on a material surface at a given temperature and
volatiles and the decomposition or reaction of the sample with
moisture content). Depending on the temperature and humidity
water or atmosphere may all influence the results.
content of the atmosphere, water can adsorb and desorb from
4.2 In addition to the methodology proposed in standards on the surface of the material to reach an equilibrium with its
coulometric titration, relative humidity sensors and LOD (see environment.
Referenced Documents, Section 2), it is recommended to
5.10 In consideration of 5.6 – 5.9, the amount of moisture in
follow the guidelines and recommendations of this guide if
powders may change progressively and be affected by the
measuring moisture in AM powder feedstocks.
storage, handling, and conditions of utilization. Thus, moisture
content should only be measured at the time of interest (for
5. Significance and Use
example, shipping, reception, and usage). If not, evaluating
5.1 This guide will help manufacturers and users of AM
how moisture and oxygen content evolve with time is recom-
powder feedstocks to identify suitable methods for measuring
mended. This can be done by exposing the powder to humidity
moisture in the feedstocks.
and evaluating how the moisture and oxygen content (using
inert gas fusion method such as described in Test Method
5.2 This guide will aid control of powder quality and allow
E1409) change with time. The effect of handling can be
powder producers and users of AM machines to assess mois-
evaluatedbymeasuringthemoistureintestsamplesbeforeand
ture content of virgin and reused powders.
after a selected operation (for example, sieving, splitting). The
5.3 This guide is intended to support acceptance and control
stability of the moisture content depends on the nature and
tests.
specific surface area of the powder and shall be evaluated for
5.4 Moisture levels are usually relatively low in metallic
every material to be tested.
powder feedstocks (typically lower than 250 µg⁄g) but could
5.11 The optimum test temperature depends on the material
be significantly more important in polymer and ceramic
and equipment used. Test conditions should be selected to
(typically lower than 10 000 µg⁄g).
recoverthemaximumamountofwaterwhiletheAMfeedstock
5.5 Moisture may affect powder processability (powder
is not modified or deteriorated. For most equipment and AM
supply and feeding, layer creation) and influence the process
powders, the maximum temperature of the equipment is not
and properties of the printed components. As different pro-
high enough to recover all the water from the samples and the
cesses and machines use powders with different characteristics
amount of water is usually underestimated.
(that is, particle size distribution and shape) andAM machines
5.12 To determine the most suitable test temperature for a
store and handle powders in different ways, the amount of
specific material, tests can be performed at different tempera-
moisture and its impact may vary significantly depending on
tures from 50 °C up to the maximum temperature of the
the feedstock, process, and machine.
equipment. The suitable temperature can be chosen to evapo-
5.6 A proportion of the water is physisorbed on the surface
rate the maximum amount of water while avoiding a modifi-
and can be easily adsorbed and desorbed.
cation (for example, oxidation or degradation) of the samples
during the test. For some materials, it may not be possible to
5.7 A fraction of the water can be strongly bonded to the
recover all water before the onset of the modification of the
surface of the powder (that is, chemisorbed) and can be
material. Consequently, the selection of the test temperature
difficult to extract even at temperatures significantly higher
shall be selected case by case.
than 100 °C. Thus, the water may not all be recovered during
the moisture analysis and some water may remain in the
5.13 Resultscanonlybecomparedifthetestsareconducted
samples. Consequently, the values obtained during the tests under similar conditions (temperature, time, heating rate, gas
may be underestimated.As water bonds differently to different
flow rate, and end criteria) and test methods have been
materials,theevaporationofwaterasafunctionoftemperature validated and compared with reference materials (see Section
may vary from one material to another.
8).
5.8 Because of the reactive nature of powders, water may 5.14 Depending on the design of the equipment, evapora-
react with the surface of the powder and form oxides and tion conditions (effective temperature seen by the samples, gas
F3606 − 22
flow, and water extraction from the surface of the powder) may 6.1.1.9 Test temperature needs to be as high as possible
differ from one model of equipment to another. Validation of without deteriorating the sample.
measurements using reference materials should be done before
6.1.1.10 As the test temperature has an impact on the
comparing results obtained in different laboratories or with
amount of water evaporated, results can only be compared
different equipment or procedures to make sure they are
together if the tests are conducted at the same temperature.
comparable.
6.1.1.11 Only the coulometric titration is appropriate to
measure the low-moisture content generally present in AM
6. Procedure
powders. The moisture content is determined in the titration
6.1 Different methods could be used to measure moisture: cell using the reaction of water with I and sulfur dioxide
leadingtotheformationofhydrogeniodideandsulfurtrioxide.
Karl Fischer (coulometric titration), relative humidity sensors,
and gravimetry (LOD).These methods are covered by different The extent of the 2I- →I2 + 2e- reaction is evaluated by
standards (Test Methods E1868, E1131, D7191, and D6869). potentiometry and used to calculate the amount of water in the
For these methods, the samples need to be heated to evaporate sample.
the water. The equipment shall have a detection limit of
6.1.1.12 The volumetric method is not precise enough for
10 µg⁄gorlower.Proceduresshouldbedevelopedtomakesure
AM powders and should not be used.
the equipment and tools are clean and dry before the sampling
6.1.2 Relative Humidity Sensor-Based Methods (see method
to prevent contamination. The following subsections describe
described in Test Method D7191):
the different methods.
6.1.2.1 Tests should be conducted following the equipment
6.1.1 Coulometric Titration (i.e., Karl Fisher):
manufacturer recommendations.
6.1.1.1 Tests should be conducted following the equipment
6.1.2.2 Before filling, the empty septum bottles should be
manufacturer recommendations.
dried 1 h at a temperature higher than the test temperature.
6.1.1.2 Before filling, the empty septum bottles should be
After drying, the bottles should be protected from humidity to
dried 1 h at a temperature higher than the test temperature.
avoid adsorption of water inside the bottle before the measure-
Afterdrying,theinsidesofthebottlesshouldbeprotectedfrom
ments.
humidity to avoid adsorption of moisture before the measure-
6.1.2.3 The amount of water coming from the bottles should
ments.
bemeasuredonthreeblanks,averaged,andsubtractedfromthe
6.1.1.3 The amount of water coming from the bottles should
amount of water measured in the powders.
bemeasuredonthreeblanks,averaged,andsubtractedfromthe
6.1.2.4 Septum bottles should be filled with the samples
amount of water measured in the powders.
before the measurements.
6.1.1.4 Septum bottles should be filled with the samples
6.1.2.5 The amount of material should be selected to have
before the measurements.
an amount of water fitting the range of sensitivity of the sensor
6.1.1.5 The amount of material should be selected to have
(see 7.5). If the order of magnitude of the amount of water is
an amount of water fitting the range of sensitivity of the
unknown, preliminary tests should be conducted to get an
titration cell (see 7.5). If the order of magnitude of the amount
appreciation of the amount of water. If the amount of moisture
of water is unknown, preliminary tests should be conducted to
measured in the preliminary tests is out of range, the mass of
get an appreciation of the amount of water. If
...