1.1 本规程涵盖了适形涡流传感器用于涂层的无损表征，而无需对涂层参考零件进行标准化。它包括以下内容: (1) 导电基板上导电涂层的厚度测量， (2) 导电涂层孔隙率增加局部区域的检测和表征，以及 (3) 测量导电基材或导电涂层上非导电涂层的厚度。本规程仅包括磁性（μ）表面的非磁性涂层≠ μ 0 )或非磁性（μ=μ 0 )基板。除了基材上的离散涂层外，本规程还可用于测量工艺的有效厚度- 影响区（例如，铝合金的喷丸层，钛合金的α层），并评估其他分层介质的状况，例如接头（例如，搭接接头和结构支架上的蒙皮）。对于特定类型的涂层零件，用户可能需要针对特定应用定制更具体的程序。 1.2 实践中涵盖了传统涡流传感器的具体用途 D7091 和 E376页 以及ASTM发布的以下试验方法: B244页 和 E1004年 . 指南中提供了适形涡流传感器阵列的使用指南 E2884 . 1.3 单位- 以国际单位制表示的数值应视为标准值。括号中给出的值是英寸的数学转换- 磅单位仅供参考，不被视为标准单位。 1.4 本标准并非旨在解决与其使用相关的所有安全问题（如有）。本标准的用户有责任在使用前制定适当的安全、健康和环境实践，并确定监管限制的适用性。 1.5 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《关于制定国际标准、指南和建议的原则的决定》中确立的国际公认标准化原则制定的。 ====意义和用途====== 4.1 适形涡流传感器- 适形涡流传感器可用于平面和曲面，包括圆角、圆柱面等。当与用于预测传感器响应的模型和适当算法一起使用时，这些传感器可以测量物理特性的变化，例如电导率或磁导率，或两者，以及任何基材上的导电涂层厚度和导电基材或导电涂层上的非导电涂层厚度。这些性能变化可用于检测和表征导电涂层内的异质区域，例如局部孔隙度较高的区域。 4.2 传感器和传感器阵列- 根据应用情况，可以使用单个传感元件传感器或传感器阵列进行涂层表征。传感器阵列提供了更好的能力来映射涂层厚度或电导率的空间变化，或两者的空间变化（例如，反映孔隙度变化），并为扫描大面积提供了更好的吞吐量。传感器占地面积的大小以及阵列内传感元件的大小和数量取决于应用要求和约束以及非导电（例如陶瓷）涂层厚度。 4.3 涂层厚度范围- 传感器性能最佳的导电涂层厚度范围取决于基板和导电涂层的电导率与可用频率范围之间的差异。 例如，具有用于阻抗测量的特定频率范围的特定传感器几何形状可为镍合金基板上的MCrAlY涂层提供可接受的性能，用于相对较宽的导电涂层厚度范围，例如从75到400μm（0.003到0.016 in）。然而，对于另一种导电涂层-基板组合，该范围可能为10至100μm（0.0004至0.004 in）。涂层表征性能也可能取决于非导电面漆的厚度。对于任何涂层系统，代表性涂层试样的性能验证对于确定最佳性能范围至关重要。对于非导电涂层，例如陶瓷涂层，厚度测量范围随着传感器空间波长的增加而增加（例如，可以使用更大的传感器绕组空间波长测量更厚的涂层）。 对于非导电涂层，当涂层的粗糙度可能对厚度测量产生重大影响时，非导电涂层粗糙度的独立测量（例如，通过轮廓术）可能会对粗糙度影响进行校正。 4.4 工艺影响区- 对于某些工艺，例如喷丸，工艺影响区可以由有效层厚度和电导率表示。这些值反过来可用于评估过程质量。必须证明这些“有效涂层”性能与工艺质量之间存在着强烈的相关性。 4.5 三个未知算法- 使用多个频率阻抗测量值和三个未知算法可以独立确定三个未知量: (1) 导电非磁性涂层的厚度， (2) 导电非磁性涂层的导电性，以及 (3) 剥离，用于测量非导电涂层厚度。 4.6 准确性- 根据材料特性和频率范围，每个涂层系统都有一个最佳测量性能范围。仪器、其空气标准化或参考基质标准化，或两者兼而有之，以及其操作允许在±15范围内确定涂层厚度 % 涂层厚度在最佳范围内且在±30范围内的真实厚度 % 超出最佳范围。某些应用程序可能需要更好的性能。 4.7 传感器响应数据库- 传感器响应数据库可用于表示传感器的模型响应。这些数据库可能基于物理模型或经验关系。数据库列出了感兴趣的特性中相关范围内的预期传感器响应（例如，感测元件和驱动绕组之间的复跨阻的实部和虚部或幅值和相位）。涂层基材材料的示例属性是基材的磁导率或电导率，或两者，涂层的电导率和厚度，以及剥离。数据库中属性值的范围应涵盖待检查材料系统的预期属性范围。

1.1 This practice covers the use of conformable eddy current sensors for nondestructive characterization of coatings without standardization on coated reference parts. It includes the following: (1) thickness measurement of a conductive coating on a conductive substrate, (2) detection and characterization of local regions of increased porosity of a conductive coating, and (3) measurement of thickness for nonconductive coatings on a conductive substrate or on a conductive coating. This practice includes only nonmagnetic coatings on either magnetic (μ ≠ μ 0 ) or nonmagnetic (μ = μ 0 ) substrates. In addition to discrete coatings on substrates, this practice can also be used to measure the effective thickness of a process-affected zone (for example, shot peened layer for aluminum alloys, alpha case for titanium alloys) and to assess the condition of other layered media such as joints (for example, lap joints and skin panels over structural supports). For specific types of coated parts, the user may need a more specific procedure tailored to a specific application. 1.2 Specific uses of conventional eddy current sensors are covered by Practices D7091 and E376 and the following test methods issued by ASTM: B244 and E1004 . Guidance for the use of conformable eddy current sensor arrays is provided in Guide E2884 . 1.3 Units— The values stated in SI units are to be regarded as standard. The values given in parentheses are mathematical conversions to inch-pound units that are provided for information only and are not considered standard. 1.4 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. 1.5 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 ====== 4.1 Conformable Eddy Current Sensors— Conformable, eddy current sensors can be used on both flat and curved surfaces, including fillets, cylindrical surfaces, etc. When used with models for predicting the sensor response and appropriate algorithms, these sensors can measure variations in physical properties, such as electrical conductivity or magnetic permeability, or both, as well as thickness of conductive coatings on any substrate and nonconductive coatings on conductive substrates or on a conducting coating. These property variations can be used to detect and characterize heterogeneous regions within the conductive coatings, for example, regions of locally higher porosity. 4.2 Sensors and Sensor Arrays— Depending on the application, either a single-sensing element sensor or a sensor array can be used for coating characterization. A sensor array provides a better capability to map spatial variations in coating thickness or conductivity, or both (reflecting, for example, porosity variations), and provides better throughput for scanning large areas. The size of the sensor footprint and the size and number of sensing elements within an array depend on the application requirements and constraints, and the nonconductive (for example, ceramic) coating thickness. 4.3 Coating Thickness Range— The conductive coating thickness range over which a sensor performs best depends on the difference between the electrical conductivity of the substrate and conductive coating and available frequency range. For example, a specific sensor geometry with a specific frequency range for impedance measurements may provide acceptable performance for an MCrAlY coating over a nickel-alloy substrate for a relatively wide range of conductive coating thickness, for example, from 75 to 400 μm (0.003 to 0.016 in.). Yet, for another conductive coating-substrate combination, this range may be 10 to 100 μm (0.0004 to 0.004 in.). The coating characterization performance may also depend on the thickness of a nonconductive topcoat. For any coating system, performance verification on representative coated specimens is critical to establishing the range of optimum performance. For nonconductive coatings, such as ceramic coatings, the thickness measurement range increases with an increase of the spatial wavelength of the sensor (for example, thicker coatings can be measured with larger sensor winding spatial wavelength). For nonconductive coatings, when roughness of the coating may have a significant effect on the thickness measurement, independent measurements of the nonconductive coating roughness, for example, by profilometry, may provide a correction for the roughness effects. 4.4 Process-Affected Zone— For some processes, for example, shot peening, the process-affected zone can be represented by an effective layer thickness and conductivity. These values can in turn be used to assess process quality. A strong correlation must be demonstrated between these “effective coating” properties and process quality. 4.5 Three-Unknown Algorithm— Use of multiple-frequency impedance measurements and a three-unknown algorithm permits independent determination of three unknowns: (1) thickness of conductive nonmagnetic coatings, (2) conductivity of conductive nonmagnetic coatings, and (3) lift-off that provides a measure of the nonconductive coating thickness. 4.6 Accuracy— Depending on the material properties and frequency range, there is an optimal measurement performance range for each coating system. The instrument, its air standardization or reference substrate standardization, or both, and its operation permit the coating thickness to be determined within ±15 % of its true thickness for coating thickness within the optimal range and within ±30 % outside the optimal range. Better performance may be required for some applications. 4.7 Databases for Sensor Response— Databases of sensor responses may be used to represent the model response for the sensor. These databases may be based upon physical models or empirical relations. The databases list expected sensor responses (for example, the real and imaginary parts or the magnitude and phase of the complex transimpedance between the sense element and drive winding) over relevant ranges in the properties of interest. Example properties for a coated substrate material are the magnetic permeability or electrical conductivity of the substrate, or both, the electrical conductivity and thickness of the coating, and the lift-off. The ranges of the property values within the databases should span the expected property ranges for the material system to be examined.