**1. Introduction**

The intensive wear of machine and apparatus parts in mining, quarrying, petrochemical, metallurgical, cement, construction, and power generation industries, among others, drives increasing demand for wear-resistant plates and liners [1–5].

Wear-resistant materials are dedicated alloys with supreme hardness that are simultaneously weldable and resistant to moderate impact loading. Contemporary wear-resistant steels, due to high metallurgical purity, are characterized by high strength, good weldability, workability, and acceptable machinability. The production costs of these steels, however, remain high [6–11].

Among the alternatives to the above-mentioned cases are prefabricated wear-resistant composite plates manufactured mainly by automated arc hardfacing, vacuum furnace powder melting, or metallurgical bonding of the base carbon steel plate with a wear-resistant surface layer. Hardfaced wear-resistant plates demonstrate significantly better wear resistance compared to wear-resistant hardened plates [12–18]. The gains from hardfaced composite wear plates primarily include increased durability, reduced time and cost of repairs, and increased machine operation safety [15,19,20].

The chemical composition and microstructure of the surface layer are chosen to achieve the highest wear resistance and durability of the finished machine and apparatus components. The impact of alloying elements on the hardness of the surface layer is diverse. For wear-resistant steels, high hardness is achieved by a melting process in suitable metallurgical conditions and the addition of set quantities of carbon, manganese, chromium, niobium, molybdenum, and thermal hardening. For wear-resistant composite plates, surface hardness is achieved by the formation of carbon metal compounds in the form of discrete hard particles, known as carbides [6,21,22].

Iron-chromium-carbon alloys are used in conditions where abrasion resistance is required. Their unique abrasive wear resistance results primarily from high volume and the decomposition of the hard carbide fraction in the weld metal matrix. The study of Fe-Cr-C alloy microstructures has demonstrated that these types of materials contain hypoeutectic, eutectic, and hypereutectic structures. Alloys containing 1.8–3.6 mass% carbon and 11–30 mass% chromium are superior in terms of wear, corrosion, and oxidation resistance, and have been adopted as abrasion resistance materials for wear-resistant parts in the mining industry. Primary carbides form in large amounts at higher carbon concentrations. High chromium and carbon contents in weld metal promote the formation of extreme high-hardness chromium carbide particles (1700 HV), which are embedded in significantly more ductile yet hard metal matrices with an average hardness of approximately 700 HV (60 HRC). Due to the presence of these constituents, a hardness level from 600 HV to 840 HV (55–65 HRC) in the surface layer is achieved [6,18].

The wear resistance achieved by hardfaced layers with carbide compounds (mainly M7C<sup>3</sup> and M3C) with hardness in the range of 1500–3000 HV is more than a few times higher than widespread wear-resistant materials [1,23,24].

The formation of alloying carbide elements is not the sole criterion in the consideration for the selection of suitable hardfaced composite wear-resistant plates. The shape and distribution of the carbide are also vital to achieving high wear resistance. The highest wear resistance is achieved when elongated cylindrical chromium carbides are situated perpendicularly to the wear-resistant layer surface. Tightly secured by type and the shape of the metal–ceramic interface, uniformly distributed carbides in a hard metal matrix act as a wear barrier, provided that they are resistant to cracking and pulling from the matrix. The lowest wear resistance is observed when chromium carbides are situated parallel to the layer surface due to the increased chance of carbide cracking and pulling from the metal matrix. The shape and orientation of carbides can be controlled to an extent by cored-wire composition selection and proper hardfacing parameters [25].

The microstructure and hardness of the most important properties of wear-resistant materials contribute to resistance to different types of tribological wear. The hardness of the material is directly dependent on the microstructure and is the easiest material property to measure. However, it is often falsely assumed as the single most important criterion in the assessment of wear-resistant materials. The hardness of the two materials can be identical, whereas their wear resistance can be significantly different due to differences in the microstructure and their impact on the hardness [26]. In the majority of cases, however, the increase in hardness coincides with the increase in wear resistance, especially in hardfaced composite wear plates.

Although there is a wide range of hardfacing electrodes, wires, and filler metals commercially available for protection against abrasion wear, the industry is constantly looking for new material solutions. Chromium-rich hardfacing alloys are commonly used due to their low cost and availability; however, more expensive tungsten- or vanadium-rich alloys offer improved welding properties due to their suitable combination of hardness and toughness. According to Kim et al. [27], covered tubular electrodes with a metallic and carbides core can also be used, especially when abrasion occurs with other wear mechanisms, such as erosion, corrosion, and moderate shock load. The basic surfacing techniques are oxyacetylene powder surfacing using a modular spray-fuse system, manual metal arc surfacing, and submerged arc surfacing. Other surfacing processes can also be used, ranging from conventional techniques, such as gas flame surfacing, to new and modern processes, such as plasma powder transferred arc surfacing and laser metal deposition techniques. The manual metal arc surfacing technique is frequently used for hardfacing applications due to its adaptability and cost-effectiveness.

The maintenance of wear plates, which includes wear assessment and replacement, is a major component of very high operating costs. Several research centers, mainly from the USA, Australia, and China, are currently conducting research on a wear detection system for wear plates in an operational environment, which would improve efficiency, safety, and profitability in the mining sector. Designing such a system, however, requires obtaining significant quantitative and qualitative data on the phenomenon of abrasive wear, which is to be supported by the presented research.
