1.1 本标准提供了用于添加剂制造（AM）的粉末原料中水分的测量指南。它适用于金属、陶瓷和聚合物AM粉末原料。 1.2 本指南描述了通常用于测量湿度的测试方法及其相关标准。 1.3 本指南提供了如何应用测试方法使其适用于AM粉末表征的最佳实践指南。 1.4 本指南适用于在10 µg/g至10000 µg/g。 1.5 以国际单位制表示的值应视为标准值。本标准不包括其他测量单位。 1.6 本标准并不旨在解决与其使用相关的所有安全问题（如有）。本标准的使用者有责任在使用前建立适当的安全、健康和环境实践，并确定监管限制的适用性。 1.7 本国际标准是根据世界贸易组织技术性贸易壁垒（TBT）委员会发布的《国际标准、指南和建议制定原则决定》中确立的国际公认标准化原则制定的。 =====意义和用途====== 5.1 本指南将帮助AM粉末原料的制造商和用户确定测量原料中水分的合适方法。 5.2 本指南将有助于控制粉末质量，并允许粉末生产商和AM机器用户评估未经处理和重复使用的粉末的水分含量。 5.3 本指南旨在支持验收和控制测试。 5.4 金属粉末原料中的水分含量通常相对较低（通常低于250 µg/g），但在聚合物和陶瓷中可能更重要（通常低于10000 µg/g）。 5.5 水分可能会影响粉末的加工性能（粉末供应和供给、层的形成），并影响印刷部件的工艺和性能。由于不同的工艺和机器使用的粉末具有不同的特性（即粒度分布和形状），AM机器以不同的方式储存和处理粉末，因此水分的量及其影响可能会因原料、工艺和机器的不同而显著不同。 5.6 一定比例的水物理吸附在表面上，易于吸附和解吸。 5.7 一部分水可以牢固地结合到粉末表面（即化学吸附），并且即使在显著高于100℃的温度下也很难提取 °C。因此，在水分分析期间，水可能不会全部被回收，一些水可能残留在样品中。 因此，测试期间获得的值可能被低估。由于水与不同材料的结合方式不同，水的蒸发量随温度的变化可能因材料而异。 5.8 由于粉末的反应性质，水可能与粉末表面反应并形成氧化物和氢氧化物。因此，即使粉末储存在紧密密封的容器中，水分的量也可能随时间变化。当粉末被加热时，粉末与水的反应也可能在分析过程中发生。该反应将减少粉末表面的可用水量，并可能影响结果（即，低估测量的水量）。如果预计会发生此类反应，应评估其对测量的影响。这可以使用氧分析来评估随时间或在测试期间形成的氧化物的量。 5.9 吸附在粉末表面上的水的量取决于温度和相对湿度，并由水分吸附等温线（在给定温度和水分含量下材料表面上的平衡水分含量）确定。根据大气的温度和湿度含量，水可以从材料表面吸附和解吸，以达到与环境的平衡。 5.10 考虑到 5.6 – 5.9 ，粉末中的水分含量可能会逐渐变化，并受储存、处理和使用条件的影响。因此，应仅在感兴趣的时间（例如，装运、接收和使用）测量含水量。如果没有，建议评估水分和氧气含量随时间的变化。这可以通过将粉末暴露在潮湿环境中并评估湿度和氧气含量（使用惰性气体熔化法，如试验方法中所述 1409年 )随时间变化。可通过在选定操作（例如筛分、分离）前后测量测试样品中的水分来评估处理效果。含水量的稳定性取决于粉末的性质和比表面积，并应对每种待测试材料进行评估。 5.11 最佳测试温度取决于使用的材料和设备。应选择试验条件，以在AM原料未改性或变质的情况下回收最大量的水。对于大多数设备和AM粉末，设备的最高温度不足以从样品中回收所有的水，并且通常低估了水的量。 5.12 为了确定特定材料的最合适测试温度，可以在50 °C至设备最高温度。 可以选择合适的温度以蒸发最大量的水，同时避免测试期间样品的变质（例如氧化或降解）。对于某些材料，可能不可能在材料改性开始之前回收所有水。因此，应逐个选择试验温度。 5.13 只有在类似条件（温度、时间、加热速率、气体流速和终点标准）下进行试验，且试验方法已得到验证并与参考材料进行比较时，才能比较结果（见第节 8. ). 5.14 根据设备的设计，蒸发条件（样品的有效温度、气流和粉末表面的水提取）可能因设备型号而异。 在比较不同实验室或使用不同设备或程序获得的结果之前，应使用参考材料验证测量结果，以确保其具有可比性。

1.1 This standard provides guidelines for measuring moisture in powder feedstock used in additive manufacturing (AM). It applies to metallic, ceramic, and polymer AM powder feedstocks. 1.2 This guide provides a description of test methods commonly used to measure moisture and references to their associated standards. 1.3 This guide provides best practice guidance on how to apply the test methods to make them suitable for AM powder characterization. 1.4 This guide is suitable for measuring moisture in AM powder feedstock over the range of 10 µg/g to 10 000 µg/g. 1.5 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. 1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. 1.7 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. ====== Significance And Use ====== 5.1 This guide will help manufacturers and users of AM powder feedstocks to identify suitable methods for measuring moisture in the feedstocks. 5.2 This guide will aid control of powder quality and allow powder producers and users of AM machines to assess moisture content of virgin and reused powders. 5.3 This guide is intended to support acceptance and control tests. 5.4 Moisture levels are usually relatively low in metallic powder feedstocks (typically lower than 250 µg/g) but could be significantly more important in polymer and ceramic (typically lower than 10 000 µg/g). 5.5 Moisture may affect powder processability (powder supply and feeding, layer creation) and influence the process and properties of the printed components. As different processes and machines use powders with different characteristics (that is, particle size distribution and shape) and AM machines store and handle powders in different ways, the amount of moisture and its impact may vary significantly depending on the feedstock, process, and machine. 5.6 A proportion of the water is physisorbed on the surface and can be easily adsorbed and desorbed. 5.7 A fraction of the water can be strongly bonded to the surface of the powder (that is, chemisorbed) and can be difficult to extract even at temperatures significantly higher than 100 °C. Thus, the water may not all be recovered during the moisture analysis and some water may remain in the samples. Consequently, the values obtained during the tests may be underestimated. As water bonds differently to different materials, the evaporation of water as a function of temperature may vary from one material to another. 5.8 Because of the reactive nature of powders, water may react with the surface of the powder and form oxides and hydroxides. Thus, the amount of moisture may change with time even if the powder is stored in a tightly sealed container. Reaction of the powder with water may also happen during the analysis as the powder is heated up. This reaction will reduce the amount of water available at the surface of the powder and may impact the results (that is, underestimate the amount of water measured). If such reactions are expected to occur, their impact on the measurements should be evaluated. This can be done using oxygen analysis to evaluate the amount of oxide formed with time or during a test. 5.9 The amount of water adsorbed on the surface of a powder depends on temperature and relative humidity and is determined by moisture sorption isotherm (water content in equilibrium on a material surface at a given temperature and moisture content). Depending on the temperature and humidity content of the atmosphere, water can adsorb and desorb from the surface of the material to reach an equilibrium with its environment. 5.10 In consideration of 5.6 – 5.9 , the amount of moisture in powders may change progressively and be affected by the storage, handling, and conditions of utilization. Thus, moisture content should only be measured at the time of interest (for example, shipping, reception, and usage). If not, evaluating how moisture and oxygen content evolve with time is recommended. This can be done by exposing the powder to humidity and evaluating how the moisture and oxygen content (using inert gas fusion method such as described in Test Method E1409 ) change with time. The effect of handling can be evaluated by measuring the moisture in test samples before and after a selected operation (for example, sieving, splitting). The stability of the moisture content depends on the nature and specific surface area of the powder and shall be evaluated for every material to be tested. 5.11 The optimum test temperature depends on the material and equipment used. Test conditions should be selected to recover the maximum amount of water while the AM feedstock is not modified or deteriorated. For most equipment and AM powders, the maximum temperature of the equipment is not high enough to recover all the water from the samples and the amount of water is usually underestimated. 5.12 To determine the most suitable test temperature for a specific material, tests can be performed at different temperatures from 50 °C up to the maximum temperature of the equipment. The suitable temperature can be chosen to evaporate the maximum amount of water while avoiding a modification (for example, oxidation or degradation) of the samples during the test. For some materials, it may not be possible to recover all water before the onset of the modification of the material. Consequently, the selection of the test temperature shall be selected case by case. 5.13 Results can only be compared if the tests are conducted under similar conditions (temperature, time, heating rate, gas flow rate, and end criteria) and test methods have been validated and compared with reference materials (see Section 8 ). 5.14 Depending on the design of the equipment, evaporation conditions (effective temperature seen by the samples, gas flow, and water extraction from the surface of the powder) may differ from one model of equipment to another. Validation of measurements using reference materials should be done before comparing results obtained in different laboratories or with different equipment or procedures to make sure they are comparable.