Abstract
The performance of the “base-applied layer” system, that forms the contact surface of parts that are subject to intensive wear, significantly depends on the gradient of mechanical characteristics in depth in the near-surface areas of contact parts. That is why the initial data before the design of the technology determines the hardness of the base material and the requirements for the material of the layer that should be applied during restoration or strengthening. This usually takes into account the initial mechanical characteristics of the new part, without taking into account the changes that occur with the material during operation, which is often accompanied by prolonged thermal exposure. Ignoring this fact during the development of renovation technology can significantly reduce its effectiveness. It is also important to know the value of hardness and microhardness in order to adequately assess the processes that accompany the wear of parts and predict its intensity.
 Therefore, when restoring each specific part after its wear, it is necessary to take into account the specific changes that have occurred in the surface layer of the contact surface. The aim of the study was to experimentally determine the hardness and microhardness of the surface layer material in the areas of greatest change in the initial geometry of the links and rollers of the continuous track to take into account the values obtained while developing their renovation technology.
 Studies of the distribution of hardness in the cross section of the new links revealed the initial uneven, with a decrease in hardness to the sides, thermal hardening of only the working surface. During operation (as a consequence of friction-deformation hardening) there is a decrease in hardness in depth by HRC 3...5 and alignment in the width of the working area to the level of HRC 25...33 against initial HRC 12...20. Studies of static microhardness in the cross section of new and worn rollers revealed the initial state of the material as inhomogeneous, which in the process of wear can be stabilized due to repeated hardening-softening. According to these changes, the maximum allowable load is estimated and it is determined that the heat treatment mode in the manufacture of new parts does not provide the required properties of the surface layer. This should be taken into account when selecting the material of the surface layers, which should be welded when restoring worn-out links and rollers, as well as when appointing the next heat treatment.
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