Methodological and Metrological Aspects of Materials Mechanical Properties Measurements by Instrumented Indentation

Features of Measuring the Hardness of a Metal Surface Modified with Ultrafine Particles of Minerals

“…There are a number of methodological sources of uncertainty in the results of measurements of hardness by the above methods: 1) hardware related to the calibration of the measuring installation [8]; 2) methodological associated with assumptions in the calculation methodology [8,15]; 3) sources associated with the physicomechanical properties of the studied material [16,17]. Without considering the hardware and methodological components of the uncertainty of the measurement results by the Vickers and industrial indentation methods, we note the sources of uncertainty associated with the physical properties of the mineral coatings of the metal surface.…”

“…An additional difference in the results of measurements performed by two methods at shallow indentation depths, which is clearly fixed in Figure 9, can be made by the fact that the object under study is a complex structured material [1], consisting of a metal matrix and fine particles distributed over the depth of the sample. Given that when calculating the values of hardness and elastic modulus from the load-injection diagram according to the standard method [8,9], all the calculation formulas are deduced from the assumptions about the interaction of the indenter with a homogeneous isotropic half-space [15,17], the complex structure of the distribution of particles and how consequence, properties, can lead to distortion of the results. A similar overestimation of hardness values at a small indentation depth, measured on thin modified layers of various metals and alloys, has been observed in many works (see, for example, [18]).…”

“…The most common method for determining the hardness of thin modified layers is instrumental indentation, which is the basis of the ISO 14577 standard. The essence of the measurement method consists in the process of indenting a trihedral diamond pyramid (Berkovich pyramidal indenter) with recording the indentation diagram and then calculating the hardness of the dependence of the applied force on the implementation in accordance with standard ISO 14577 [8,9]. Also, to measure the hardness of thin microlayers, the Vickers method of measuring microhardness (ISO 6507 standard) is used, which is methodologically close to the instrumental indentation method [10].…”

“…The difference between the methods is that in the Vickers method, hardness is defined as the ratio of the applied load to the surface area of the restored fingerprint, and in the industrial indentation method, the hardness is equal to the ratio of the maximum applied load to the projected area of the unrepaired fingerprint [14,15]. In general, hardness, as a dimensionless quantity, characterizes the behavior of the material under strictly specified test conditions [12], is not a function of primary physical quantities and depends on the measurement technique [8,11]. Therefore, situations are possible in which differences in the hardness determination procedures by these two methods can lead to differences in the results of hardness measurements of thin modified metal layers with a thickness of several tens of microns, which is typical when microparticles are modified with minerals.…”

“…Therefore, situations are possible in which differences in the hardness determination procedures by these two methods can lead to differences in the results of hardness measurements of thin modified metal layers with a thickness of several tens of microns, which is typical when microparticles are modified with minerals. On the one hand, the instrumental indentation method provides the largest locality and precision of measurements [8,9,13,14], the largest of all existing methods for measuring the hardness of thin layers, on the other hand, the hardness tester that implements the instrumental indentation method is a complex laboratory complex, and the price of the instrument, implementing this method, often differs by an order of magnitude from the price of a Vickers microhardness tester, which makes it difficult to use when scaling the technology. It should also be noted that the implementation of both methods in modern instruments provides automatic hardness measurement, touch control, and automatic focusing.…”