Structure and volumetric hardness of materials
Authors:   National University of Life and Environmental Sciences of Ukraine, Kyiv, О. E. Semenovskyi , O. V. Mykhnian ,   Physico-Technological Institute of Metals and Alloys of NAS of Ukraine, Kyiv
Published: February 2023

In mechanical engineering, the main parameters that determine the use of materials are their operational characteristics, which are determined by mechanical properties. The material must meet the specified parameters of strength, hardness, elasticity and viscosity. Only the method of determining the hardness of the material, in addition to physical methods, allows conducting research without making special samples without destroying the part. At the same time, the factor that the rest of the properties are indirectly related to the hardness parameter is taken into account. The classic definition of the hardness of materials as a mechanical property is the ability of a solid body to resist the penetration of another harder body into it. Based on this, the hardness is characterized by the value, that is, the volume by which a harder body penetrates the material under study. Currently, there are extremely many methods for determining hardness, but all of them are side effects. Even the most standardized methods take into account the area of interaction between the indenter and the test material, which is highly dependent on the geometry of the indenter and the load. The volumetric characteristic of hardness, which is proposed in this work, takes into account both the load and the geometry of the indenter. In modern metallurgy, it is customary to compare the units of all hardness measurement methods for their practical comparison, depending on the scale factor, by converting their values to such generally accepted methods as Brinell, Rockwell, or Vickers. For research, the authors used the developed methodology, which involves the use of a single characteristic - volume hardness of materials. This characteristic does not require the use of transitional tables of hardness units obtained by different methods. Volumetric hardness, unlike other methods, really corresponds to the physical content of the hardness characteristic, as the ability of a material to resist the incorporation of another, harder material into it. It is characterized by the displaced specific volume. Mathematically, it is characterized by the effort required to displace one cubic millimeter of a substance. The purpose of this work was a visual demonstration of the possibility of applying the concept of volume hardness as a characteristic that corresponds to the physical meaning of this property of materials. Show that the proposed technique makes it possible to compare the hardness of materials with a wide range of properties. To ensure a wide range of research, materials with different internal structures were selected, depending on the chemical composition of the alloys, as well as the mode of chemical and thermal treatment. Comparisons of the results obtained by different methods of hardness research were made and it was shown that the bulk hardness can clearly characterize and generalize these results. Keywords: volumetric hardness, mechanical properties, complex alloying, steel, heat treatment.