1.1 本试验方法包括测定高级陶瓷的努氏压痕硬度。在该试验中，用预定的力将规定形状的尖的、菱形的、金字塔形的金刚石压头压入陶瓷表面，以产生相对较小的永久压痕。使用光学显微镜测量永久压痕的长对角线的表面投影。长对角线的长度和施加的力用于计算努氏硬度，努氏硬度表示材料对努氏压头穿透的阻力。 1.2 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。 1.3 单位- 在进行努氏和维氏硬度试验时，规定的力水平单位为克力（gf）和千克力（kgf）。本标准规定了国际单位制（SI）中的力和长度单位；即，力单位为牛顿（N），长度单位为毫米或微米。然而，由于历史先例和持续的普遍使用，偶尔会提供gf和kgf单位的力值以供参考。 本试验方法规定，努氏硬度应以GPa为单位或以无量纲努氏硬度值表示。 1.4 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。 1.5 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《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 对于高级陶瓷，努氏压头用于产生压痕。用光学显微镜测量长对角线的表面投影。 5.2 努氏压痕硬度是用于表征高级陶瓷的许多财产之一。已经尝试将努氏压痕硬度与其他硬度标度相关联，但没有普遍接受的方法可用。此类转换范围有限，应谨慎使用，但通过比较试验获得可靠转换基础的特殊情况除外。 5.3 对于高级陶瓷，努氏压痕通常优于维氏压痕，因为在相同的力下，努氏长对角线长度比维氏对角线长度长2.8倍，开裂问题也小得多 ( 1. ) . 5. 另一方面，努氏压痕的细长尖端更难精确辨别，尤其是在对比度较低的材料中。在本试验方法中选择的压痕力设计为在常规显微硬度设备中产生尽可能大的压痕，但不会大到导致开裂。 5.4 努氏压痕比相同力下的维氏压痕浅。努氏压痕可用于评估涂层硬度。 5.5 努氏硬度由施加的力除以试样表面上的投影压痕面积的比率计算得出。假设窄对角线的弹性回弹可以忽略不计。（维氏压头也用于测量硬度，但维氏硬度是根据施加的力与未变形压头四个面的接触面积之比计算的。 ) 5.6 完整的硬度表征包括对大范围压痕力的测量。陶瓷的努氏硬度通常随着压痕尺寸或压痕力的增加而降低，如 图1 . 6. 这种趋势被称为压痕尺寸效应（ISE）。在足够大的压痕尺寸或力（载荷）下，硬度接近平台恒定硬度。获得恒定硬度所需的测试力因陶瓷而异。本标准中规定的试验力应足够大，以使硬度接近或处于稳定状态，但不应太大而导致过度开裂。 建议对ISE进行全面表征，但这超出了在单一指定力下测量硬度的测试方法的范围。 图1 陶瓷的典型压痕尺寸效应（ISE）曲线（所示数据为NIST SRM 2830氮化硅）

1.1 This test method covers the determination of the Knoop indentation hardness of advanced ceramics. In this test, a pointed, rhombic-based, pyramidal diamond indenter of prescribed shape is pressed into the surface of a ceramic with a predetermined force to produce a relatively small, permanent indentation. The surface projection of the long diagonal of the permanent indentation is measured using a light microscope. The length of the long diagonal and the applied force are used to calculate the Knoop hardness which represents the material’s resistance to penetration by the Knoop indenter. 1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. 1.3 Units— When Knoop and Vickers hardness tests were developed, the force levels were specified in units of grams-force (gf) and kilograms-force (kgf). This standard specifies the units of force and length in the International System of Units (SI); that is, force in newtons (N) and length in mm or μm. However, because of the historical precedent and continued common usage, force values in gf and kgf units are occasionally provided for information. This test method specifies that Knoop hardness be reported either in units of GPa or as a dimensionless Knoop hardness number. 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 ====== 5.1 For advanced ceramics, Knoop indenters are used to create indentations. The surface projection of the long diagonal is measured with optical microscopes. 5.2 The Knoop indentation hardness is one of many properties that is used to characterize advanced ceramics. Attempts have been made to relate Knoop indentation hardness to other hardness scales, but no generally accepted methods are available. Such conversions are limited in scope and should be used with caution, except for special cases where a reliable basis for the conversion has been obtained by comparison tests. 5.3 For advanced ceramics, the Knoop indentation is often preferred to the Vickers indentation since the Knoop long diagonal length is 2.8 times longer than the Vickers diagonal for the same force, and cracking is much less of a problem ( 1 ) . 5 On the other hand, the long slender tip of the Knoop indentation is more difficult to precisely discern, especially in materials with low contrast. The indentation forces chosen in this test method are designed to produce indentations as large as may be possible with conventional microhardness equipment, yet not so large as to cause cracking. 5.4 The Knoop indentation is shallower than Vickers indentations made at the same force. Knoop indents may be useful in evaluating coating hardnesses. 5.5 Knoop hardness is calculated from the ratio of the applied force divided by the projected indentation area on the specimen surface. It is assumed that the elastic springback of the narrow diagonal is negligible. (Vickers indenters are also used to measure hardness, but Vickers hardness is calculated from the ratio of applied force to the area of contact of the four faces of the undeformed indenter.) 5.6 A full hardness characterization includes measurements over a broad range of indentation forces. Knoop hardness of ceramics usually decreases with increasing indentation size or indentation force such as that shown in Fig. 1 . 6 The trend is known as the indentation size effect (ISE). Hardness approaches a plateau constant hardness at sufficiently large indentation size or forces (loads). The test forces that are needed to achieve a constant hardness vary with the ceramic. The test force specified in this standard is intended to be sufficiently large that hardness is either close to or on the plateau, but not so large as to introduce excessive cracking. A comprehensive characterization of the ISE is recommended but is beyond the scope of this test method which measures hardness at a single, designated force. FIG. 1 A Typical Indentation Size Effect (ISE) Curve for a Ceramic (The data shown are for NIST SRM 2830 silicon nitride)