ISO/TC 164/SC 3 - Hardness testing

This document specifies the instrumented indentation method for testing at elevated temperature for determination of hardness and other materials parameters at temperatures above ambient. Elevated temperature testing is defined in this document to be when the test piece and indenter tip are heated above the ambient conditions of the instrument to a controlled and measured temperature; insulating shielding is used to enclose the hot zone to reduce heating effects so that the majority of the instrumented indentation testing machine is at ambient conditions. This document is restricted to test machines that have been traceably calibrated and pass an indirect verification according to ISO 14577-2 when operating at elevated temperature to ensure that any effects on ambient sensors caused by the presence of a hot zone are accounted for. This document covers instrumented indentation testing at elevated temperatures in air, in inert or reducing gaseous environments, or in vacuum. This document provides a method for instrumented indentation testing at elevated temperature with both the indenter tip and test piece actively heated, and with independent feedback control and temperature measurement of both the indenter tip and test piece. This document provides a method for estimation of the uncertainty of the contact temperature. The uncertainty increases as the thermal conductivity of the test piece decreases. It is left to the user to decide if that uncertainty is fit for their purpose. The test method in this document is not applicable to: — instrumented indentation testing where there is no direct measurement of the temperature of the indenter tip body itself; — instrumented indentation testing where above ambient temperatures are obtained by placing the entire instrument in a hot box to achieve iso-thermal heating of the whole system. These systems typically only achieve limited elevated temperature; — instrumented indentation testing with active heating of the test piece but only passive heating of the indenter, e.g. by proximity to the hot test piece and thermal conduction through the indentation contact, hot gas, or any combination.

This document specifies the method for Rockwell regular and Rockwell superficial hardness tests for scales A, B, C, D, E, F, G, H, K, 15N, 30N, 45N, 15T, 30T, and 45T for metallic materials and is applicable to stationary and portable hardness testing machines. For specific materials and/or products, other specific International Standards apply (e.g. ISO 3738-1 and ISO 4498).

This document specifies a method for the calibration of reference blocks to be used for the indirect and daily verification of Rockwell hardness testing machines and indenters, as specified in ISO 6508-2. This document also specifies requirements for Rockwell machines and indenters used for calibrating reference blocks and specifies methods for their calibration and verification. Attention is drawn to the fact that the use of hard metal for ball indenters is considered to be the standard type of Rockwell indenter ball.

This document specifies two separate methods of verification of testing machines (direct and indirect) for determining Rockwell hardness in accordance with ISO 6508-1, together with a method for verifying Rockwell hardness indenters. The direct verification method is used to determine whether the main parameters associated with the machine function, such as applied force, depth measurement, and testing cycle timing, fall within specified tolerances. The indirect verification method uses a number of calibrated reference hardness blocks to determine how well the machine can measure a material of known hardness. This document is applicable to stationary and portable hardness testing machines. Attention is drawn to the fact that the use of tungsten carbide composite for ball indenters is considered to be the standard type of Rockwell indenter ball.

This document specifies the method of instrumented indentation test for evaluation of stress change between reference and target states using indentation force differences. This document primarily applies to measuring the stress change in a specific location and the stress difference between different locations.

This document specifies the Vickers hardness test method for the three different ranges of test force for metallic materials, including hard metals and other cemented carbides (see Table 1), metallic coatings and other inorganic coatings. The Vickers hardness test is specified in this document for lengths of indentation diagonals between 0,020 mm and 1,400 mm. Using this method to determine Vickers hardness from smaller indentations is outside the scope of this document as results would suffer from large uncertainties due to the limitations of optical measurement and imperfections in tip geometry. The Vickers hardness specified in this document is also applicable for metallic and other inorganic coatings including electrodeposited coatings, autocatalytic coatings, sprayed coatings and anodic coatings on aluminium. This document is applicable to measurements normal to the coated surface and to measurements on cross-sections, provided that the characteristics of the coating (smoothness, thickness, etc.) permit accurate readings of the diagonal of the indentation. This document is not applicable for coatings with thickness less than 0,030 mm when testing normal to the coating surface. This standard is not applicable for coatings with thickness less than 0,100 mm when testing a cross-section of the coating. ISO 14577-1 can be used for the determination of hardness from smaller indentations.” A periodic verification method is specified for routine checking of the testing machine in service by the user. For specific materials and/or products, relevant International Standards exist.

This document specifies the Knoop hardness test method for metallic materials for test forces from 0,009 807 N to 19,613 N. This document specifies Knoop hardness tests for length of the long diagonal ≥0,020 mm. Using this method to determine the Knoop hardness from smaller indentations is outside the scope of this document as results would suffer from large uncertainties due to the limitations of optical measurement and imperfections in tip geometry. The Knoop hardness test specified in this document is also applicable for metallic and other inorganic coatings including electrodeposited coatings, autocatalytic coatings, sprayed coatings and anodic coatings on aluminium. This document is applicable to measurements normal to the coated surface and to measurements on cross-sections, provided that the characteristics of the coating (smoothness, thickness, etc.) permit accurate readings of the diagonal of the indentation. This document is not applicable for coatings with thickness less than 0,007 mm when testing normal to the coating surface. This document is not applicable for coatings with thickness less than 0,020 mm when testing a cross-section of the coating. ISO 14577-1 can be used for the determination of hardness from smaller indentations. A periodic verification method is specified for routine checking of the testing machine in service by the user.

This document specifies the method of linear elastic dynamic instrumented indentation test for determination of indentation hardness and indentation modulus of materials showing elastic-plastic behaviour when oscillatory force or displacement is applied to the indenter while the load or displacement is held constant at a prescribed target value or while the indenter is continuously loaded to a prescribed target load or target depth.

ISO 6507-4:2018 gives tables of Vickers hardness for use in tests carried out in accordance with ISO 6507‑1.

ISO 6507-3:2018 specifies a method for the calibration of reference blocks to be used for the indirect verification of Vickers hardness testing machines, as specified in ISO 6507‑2. The method is applicable only for indentations with diagonals ≥0,020 mm.

ISO 6507-2:2018 specifies a method of verification and calibration of testing machines and diagonal measuring system for determining Vickers hardness in accordance with ISO 6507‑1. A direct method of verification and calibration is specified for the testing machine, indenter and the diagonal length measuring system. An indirect verification method using reference blocks is specified for the overall checking of the machine. If a testing machine is also to be used for other methods of hardness testing, it shall be verified independently for each method. ISO 6507-2:2018 is also applicable to portable hardness testing machines but not applicable to hardness testing machines based on different measurement principles, e.g. ultrasonic impedance method.

ISO 4545-3:2017 specifies the method for the calibration of reference blocks to be used for the indirect verification of Knoop hardness testing machines as specified in ISO 4545‑2. The method is applicable only for indentations with long diagonals ≥0,020 mm.

ISO 4545-2:2017 specifies the method of verification and calibration of testing machines for determining Knoop hardness for metallic materials in accordance with ISO 4545‑1. A direct method of verification and calibration is specified for the testing machine, indenter, and the diagonal length measuring system. An indirect verification method using reference blocks is specified for the overall checking of the machine. If a testing machine is also to be used for other methods of hardness testing, it will be verified independently for each method.

ISO 4545-4:2017 gives a table for the calculation of Knoop hardness values for use in tests carried out in accordance with ISO 4545‑1.

ISO 6506-2:2017 specifies methods of direct and indirect verification of testing machines used for determining Brinell hardness in accordance with ISO 6506‑1 and also specifies when these two types of verification have to be performed. The direct verification involves checking that individual machine performance parameters fall within specified limits whereas the indirect verification utilizes hardness measurements of reference blocks, calibrated in accordance with ISO 6506‑3, to check the machine's overall performance. If a testing machine is also to be used for other methods of hardness testing, it has to be verified independently for each method. ISO 6506-2:2017 is applicable to both fixed location and portable hardness testing machines. For machines that are incapable of satisfying the specified force-time profile, the direct verification of force and testing cycle can be modified by the use of Annex B.

ISO 14577-4:2016 specifies a method for testing coatings which is particularly suitable for testing in the nano/micro range applicable to thin coatings. However, the application of this method of this part of ISO 14577 is not needed if the indentation depth is such a small fraction of the coating thickness that in any possible case a substrate influence can be neglected and the coating can be considered as a bulk material. Limits for such cases are given. This test method is limited to the examination of single layers when the indentation is carried out normal to the test piece surface, but graded and multilayer coatings can also be measured in cross-section if the thickness of the individual layers or gradations is greater than the spatial resolution of the indentation process. The test method is not limited to any particular type of material. Metallic and non-metallic coatings are included in the scope of this part of ISO 14577. In this part of ISO 14577, the term coating is used to refer to any solid layer with homogeneous properties different to that of a substrate it is connected to. The method assumes that coating properties are constant with indentation depth. Composite coatings are considered to be homogenous if the structure size is less than the indentation size. The application of this part of ISO 14577 regarding measurement of indentation hardness is only possible if the indenter is a pyramid or a cone with a radius of tip curvature small enough for plastic deformation to occur within the coating. The hardness of visco-elastic materials or materials exhibiting significant creep will be strongly affected by the time taken to perform the test.

ISO 16859-2:2015 specifies methods for direct and indirect verification of test instruments used for determining Leeb hardness in accordance with ISO 16859‑1, and also describes when these two types of verification are to be performed. The direct verification involves checking that individual instrument performance parameters fall within specified limits, whereas the indirect verification utilizes hardness measurements of reference test blocks, calibrated in accordance with ISO 16859‑3, to check the overall performance of the instrument for testing in the direction of gravity. The indirect method can be used on its own for the periodic performance checking in service.

ISO 16859-3:2015 specifies a method for the calibration of reference test blocks that are used for the indirect verification of Leeb hardness testers according to ISO 16859‑2 and for the periodic checking according to ISO 16859‑1. The procedures necessary to ensure metrological traceability of the calibration machine are also specified.

ISO 16859-1:2015 covers the determination of a dynamic hardness of metallic materials using seven different Leeb scales (HLD, HLS, HLE, HLDL, HLD+15, HLC, HLG).

ISO 14577-3:2015 specifies a method for the calibration of reference blocks to use for the indirect verification of testing machines for the instrumented indentation test as specified in ISO 14577‑2:2015.

ISO 14577-1:2015 specifies the method of instrumented indentation test for determination of hardness and other materials parameters for the following three ranges: macro range: 2 N ≤ F ≤ 30 kN; micro range: 2 N > F; h > 0,2 µm; and nano range: h ≤ 0,2 µm. For the nano range, the mechanical deformation strongly depends on the real shape of indenter tip and the calculated material parameters are significantly influenced by the contact area function of the indenter used in the testing machine. Therefore, careful calibration of both instrument and indenter shape is required in order to achieve an acceptable reproducibility of the materials parameters determined with different machines. The macro and micro ranges are distinguished by the test forces in relation to the indentation depth. Attention is drawn to the fact that the micro range has an upper limit given by the test force (2 N) and a lower limit given by the indentation depth of 0,2 µm. The determination of hardness and other material parameters is given in Annex A. At high contact pressures, damage to the indenter is possible. For this reason in the macro range, hardmetal indenters are often used. For test pieces with very high hardness and modulus of elasticity, permanent indenter deformation can occur and can be detected using suitable reference materials. It is necessary that its influence on the test result be taken into account. This test method can also be applied to thin metallic and non-metallic coatings and non-metallic materials. In this case, it is recommended that the specifications in the relevant standards be taken into account (see also 6.3 and ISO 14577‑4).

ISO 14577-2:2015 specifies the method of verification and calibration of testing machines for carrying out the instrumented indentation test in accordance with ISO 14577‑1:2015. It describes a direct verification method for checking the main functions of the testing machine and an indirect verification method suitable for the determination of the repeatability of the testing machine. There is a requirement that the indirect method be used in addition to the direct method and for the periodic routine checking of the testing machine in service. It is a requirement that the indirect method of verification of the testing machine be carried out independently for each test method. ISO 14577-2:2015 is also applicable for transportable testing machines.

ISO 6506-4:2014 gives a table of the Brinell hardness values for use in tests on flat surfaces.

ISO 6506-3:2014 specifies a method for the calibration of reference blocks to be used in the indirect verification of Brinell hardness testing machines as described in ISO 6506‑2. The procedures necessary to ensure metrological traceability of the calibration machine are also specified.

ISO 6506-1:2014 specifies the method for the Brinell hardness test for metallic materials. It is applicable to both fixed location and portable hardness testing machines. For some specific materials and/or products, particular International Standards exist (e.g. ISO 4498) and make reference to this International Standard.

ISO 18265:2013 specifies the principles of the conversion of hardness values to equivalent values in other hardness scales and to estimates of tensile strength. It gives general information on the use of the conversion tables. The conversion tables in Annexes A to G apply to unalloyed and low alloy steels and cast steel, steels for quenching and tempering, steels for cold working, high speed steels, tool steels, hardmetals, and non-ferrous metals and alloys. Annex H gives information about the effects of changes of the test procedure in the standards specifying the hardness tests. Converted values obtained using ISO 18265:2013 are only directly applicable to the exact material tested. For all other materials, they provide an indicator only. In all cases, the converted values are not intended as replacements for values obtained by the correct standard method. In particular, tensile strength estimates are the least reliable converted values in ISO 18265:2013.

ISO/TR 29381:2008 describes methods for evaluating tensile properties of metallic materials (true stress-strain curve and derived parameters) using an instrumented indentation test. The ranges of application of instrumented indentation tests are in line with the classification of ISO 14577-1:2002, but the range of force recommended is from 2 N to 3 kN. ISO/TR 29381:2008 includes the following three methods, all of which are sound in principle, are capable of practical use and are appropriate for the specified materials. Method 1: representative stress and strain; Method 2: inverse analysis by FEA; Method 3: neural networks. In every method, tensile curves are derived from the experimentally measured indentation force-depth curve, from which indentation tensile properties are evaluated. The three methods described all need different user strategies and abilities to obtain the indentation tensile properties. The information required differs for each method, and is described in detail. The main assumption in the three methods is the absence of residual stress within the test piece. Existing residual stress can affect the estimation of indentation tensile properties. A procedure for evaluating residual stress using an instrumented indentation test is given for reference.

ISO 6507-1:2018 specifies the Vickers hardness test method for the three different ranges of test force for metallic materials including hardmetals and other cemented carbides.

ISO 4545-1:2017 specifies the Knoop hardness test method for metallic materials for test forces from 0,009 807 N to 19,613 N. The Knoop hardness test is specified in this document for lengths of indentation diagonals ≥0,020 mm. Using this method to determine Knoop hardness from smaller indentations is outside the scope of this document as results would suffer from large uncertainties due to the limitations of optical measurement and imperfections in tip geometry. ISO 14577-1 allows the determination of hardness from smaller indentations. A periodic verification method is specified for routine checking of the testing machine in service by the user. Special considerations for Knoop testing of metallic coatings can be found in ISO 4516.

ISO 6508-1:2016 specifies the method for Rockwell regular and Rockwell superficial hardness tests for scales A, B, C, D, E, F, G, H, K, 15N, 30N, 45N, 15T, 30T, and 45T for metallic materials and is applicable to stationary and portable hardness testing machines. For specific materials and/or products, other specific International Standards apply (for instance, ISO 3738‑1 and ISO 4498).

ISO 6508-2:2015 specifies two separate methods of verification of testing machines (direct and indirect) for determining Rockwell hardness in accordance with ISO 6508‑1:2015, together with a method for verifying Rockwell hardness indenters. The direct verification method is used to determine whether the main parameters associated with the machine function, such as applied force, depth measurement, and testing cycle timing, fall within specified tolerances. The indirect verification method uses a number of calibrated reference hardness blocks to determine how well the machine can measure a material of known hardness. The indirect method may be used on its own for periodic routine checking of the machine in service. If a testing machine is also to be used for other methods of hardness testing, it shall be verified independently for each method. ISO 6508-2:2015 is applicable to stationary and portable hardness testing machines. Attention is drawn to the fact that the use of tungsten carbide composite for ball indenters is considered to be the standard type of Rockwell indenter ball. Steel indenter balls may continue to be used only when complying with ISO 6508‑1:2015, Annex A.

ISO 6508-3:2015 specifies a method for the calibration of reference blocks to be used for the indirect and daily verification of Rockwell hardness testing machines, as specified in ISO 6508‑2:2015. Attention is drawn to the fact that the use of hard metal for ball indenters is considered to be the standard type of Rockwell indenter ball. Steel indenter balls can be used only when complying with ISO 6508‑1:2015, Annex A.

ISO 6508-1:2015 specifies the method for Rockwell regular and Rockwell superficial hardness tests (scales and applicable range of application according to Table 1) for metallic materials and is applicable to stationary and portable hardness testing machines. For specific materials and/or products, other specific International Standards apply (for instance, ISO 3738‑1 and ISO 4498). NOTE Attention is drawn to the fact that the use of tungsten carbide composite for ball indenters is considered to be the standard type of Rockwell indenter ball. Steel indenter balls are allowed to continue to be used only when complying with Annex A.

ISO 6506-2:2014 specifies methods of direct and indirect verification of testing machines used for determining Brinell hardness in accordance with ISO 6506‑1, and also specifies when these two types of verification has to be performed. The direct verification involves checking that individual machine performance parameters fall within specified limits whereas the indirect verification utilizes hardness measurements of reference blocks, calibrated in accordance with ISO 6506‑3, to check the machine's overall performance. If a testing machine is also to be used for other methods of hardness testing, it has to be verified independently for each method. ISO 6506-2:2014 is applicable to both fixed location and portable hardness testing machines. For machines that are incapable of satisfying the specified force-time profile, the direct verification of force and testing cycle can be modified by the use of Annex B.

ISO 14577-4:2007 specifies a method for testing coatings that is particularly suitable for testing in the nano/micro range applicable to thin coatings. This test method is limited to the examination of single layers when the indentation is carried out normal to the test piece surface, but graded and multilayer coatings can also be measured in cross-section if the thickness of the individual layers or gradations is greater than the spatial resolution of the indentation process. The test method is not limited to any particular type of material. Metallic, non-metallic and organic coatings are included in the scope of ISO 14577-4:2007. The application of ISO 14577-4:2007 regarding measurement of hardness is only possible if the indenter is a pyramid or a cone with a radius of tip curvature small enough for plastic deformation to occur within the coating. The hardness of visco-elastic materials, or materials exhibiting significant creep will be strongly affected by the time taken to perform the test.

ISO 6508-3:2005 specifies a method for the calibration of reference blocks to be used for the indirect verification of Rockwell hardness testing machines (scales A, B, C, D, E, F, G, H, K, N, T), as specified in ISO 6508-2.

ISO 6508-1:2005 specifies the method for Rockwell and Rockwell superficial hardness tests for metallic materials.

ISO 6508-2:2005 specifies a method of verification of testing machines for determining Rockwell hardness (scales A, B, C, D, E, F, G, H, K, N, T) in accordance with ISO 6508-1.

ISO 6507-1:2005 specifies the Vickers hardness test method for the three different ranges of test force for metallic materials. The Vickers hardness test is specified in ISO 6507-1:2005 for lengths of indentation diagonals between 0,020 mm and 1,400 mm.

ISO 6507-3:2005 specifies a method for the calibration of reference blocks to be used for the indirect verification of Vickers hardness testing machines, as specified in ISO 6507-2. The method is applicable only for indentations with diagonals greater than or equal to 0,020 mm.

ISO 6507-4:2005 gives tables of Vickers hardness for use in tests made on flat surfaces.

ISO 6507-2:2005 specifies a method of verification of testing machines for determining Vickers hardness in accordance with ISO 6507-1.

ISO 6506-2:2005 specifies a method of verification and calibration of testing machines used for determining Brinell hardness in accordance with ISO 6506-1. ISO 6506-2:2005 specifies a direct method for checking the main functions of machine operation and an indirect method suitable for the overall checking of the machine. The indirect method may be used independently for periodic routine checking of machine operation while in service. If a testing machine is also to be used for other methods of hardness testing, it should be verified independently for each method. ISO 6506-2:2005 is also applicable to portable hardness testing machines.

ISO 6506-1:2005 specifies the method for the Brinell hardness test for metallic materials and is applicable up to the limit of 650 HBW.

ISO 6506-4:2005 gives a table of the Brinell hardness values for use in tests on flat surfaces.

ISO 6506-3:2005 specifies a method for the calibration of reference blocks to be used for use in the indirect verification of Brinell hardness testing machines as described in ISO 6506-2.

ISO 4545-3:2005 specifies the method for the calibration of reference blocks to be used for the indirect verification of Knoop hardness testing machines as specified in ISO 4545-2. The method is applicable only for indentations with long diagonals greater than or equal to 0,020 mm.

ISO 4545-1:2005 specifies the Knoop hardness test method for metallic materials, for test forces from 0,098 07 N to 19,614 N. The method is recommended only for indentations with diagonals greater than or equal to 0,020 mm.

ISO 4545-2:2005 specifies the method of verification of testing machines for determining Knoop hardness for metallic materials in accordance with ISO 4545-1. It covers test forces from 0,098 07 N to 19,614 N. The method is recommended only for indentations with diagonals greater than or equal to 0,020 mm.

ISO 4545-4:2005 gives a table for the calculation of Knoop hardness values for use in tests made on flat surfaces carried out in accordance with ISO 4545-1.