This paper defines the wear process of rollers made of 20Cr4. Rollers with a diameter of 1000 mm were installed in a roller press used for the production of drop-shaped briquettes and the copper concentrate was briquetted for 1100 h. Three-dimensional (3D) geometry analysis, metallographic analysis, macroscopy, scanning electron microscopy, as well as hardness measurements were performed. It was observed that the working surface was non-uniformly worn. The smallest wear affects the molding cavities situated on the outermost edges of the ring. The wear increases as the center of the ring is approximated, and it reaches its maximum at the middle of the ring. The molding cavities also wear asymmetrically. For the shape considered in this study, the lower part of a cavity is subject to a higher wear rate. We found that the material of the working ring was carburized, but its hardness was significantly lower than required. The roller ring microstructure changes depended on the distance from the cavity’s face. An investigation of the wear mechanisms showed different types of abrasive wear, corrosive processes, and plastic deformation. The exact type and course of wear were described, depending on the location on the working surface.

Steel forging tools are subjected to a number of tribological wear mechanisms depending on the geometry and surface of the tool and the flow of the material. Thus, there is no single general tribological wear mechanism, and only the predominant wear mechanisms in this case can be indicated. The problem has been known for years, but due to its complexity research on it is still relevant. In this study, the various wear mechanisms of hot work tools are analyzed on the basis of original research. Moreover, the influence of the micro- and macrostructure of the material and of its mechanical, physical, and technological characteristics on susceptibility to a given type of wear is considered. Adhesive wear, wear caused by plastic deformation, mechanical fatigue, thermal fatigue, the influence of hardness, heat treatment, and impact strength on tool wear and the mechanisms causing this wear are discussed in addition to tribological wear mechanisms such as abrasive wear. The influence of thermomechanical history and the characteristics of the tool material, including structural anisotropy, on the wear of these tools is indicated. The analysis of wear mechanisms performed will enable more precise definition of the principles of tool material selection and tool material condition for the hot forging of steel.

The main task for a ballast bed is to transmit the sleeper pressure in a form of stress cone to the subsoil, provide proper drainage and resist the sleeper displacement. Poorly maintained ballast could severely limit the maximum speed capacity and create further problems with the structural integrity, possibly leading to a complete failure of a given rail line. To prevent the unwanted corollaries, the ballast bed has to be periodically cleaned with an appropriate machinery. In this paper the authors investigated the effect of the chemical composition on the physical properties of the ballast excavating chains made of high-manganese steels. The authors focused on the wear mechanism, work hardening ability and hardness in the cross-sections areas. A microstructure analysis was performed as well, and observations revealed divergent morphology of precipitations at the grain boundaries, which influenced the size of austenite grains. The deformation twins formed as a result of operation were noticed in the samples. Research has shown that less carbon and chromium reduces the hardness of cast steel, and it specifically affects the ability to strain hardening. The authors explained the role of adjustments in chemical composition in the operational properties of high-manganese cast steels. It has been shown in the paper that different chemical compositions affect the properties of the alloys, and this causes different types of wear. The high content of chromium increases the hardness of materials before and after plastic deformation hardening, which in the conditions of selector chains results in greater dimensional stability during wear of holes in pin joints and will be more susceptible to abrasive wear in the presence of dusts from the ballast than creep.

Hardfacing is one of the techniques used for part lifecycle elongation. Despite being used for over 100 years, there still is much to discover, as modern metallurgy provides more and more sophisticated alloys, which then have to be studied to find the best technological parameters in order to fully utilize complex material properties. One of the most efficient and versatile hardfacing approaches is Gas Metal Arc Welding technology (GMAW) and its cored-wire equivalent, known as FCAW (Flux-Cored/Cored Arc Welding). In this paper, the authors study the influence of heat input on the geometrical properties and hardness of stringer weld beads fabricated from cored wire consisting of macrocrystalline tungsten carbides in a nickel matrix. The aim is to establish a set of parameters which allow to manufacture wear-resistant overlays with high deposition rates, preserving all possible benefits of this heterogenic material. This study shows, that for a given diameter of the Ni-WC wire, there exists an upper limit of heat input beyond which the tungsten carbide crystals may exhibit undesired segregation at the root.