Special Issue “Microstructure, Fatigue and Wear Properties of Steels”

Sustainable manufacturing is a trending topic within the industry. The steel production process is known to generate carbon emissions; however, to move towards “eco-friendly steel” production, enhancing steel’s service life is a viable strategy [1,2]. It has been demonstrated that controlling steel’s microstructure is an effective way to achieve a longer lifespan for steel products.

Surface modification is a proven technique for enhancing the longevity of steel components. Employing coatings as a corrosion prevention strategy not only minimizes the repair expenses caused by corrosion, but also prevents accidents due to degraded structures or machinery. Cui et al. [3] examined the corrosion resistance of steel plates coated with enamel modified by quartz sand. Their findings indicated that these quartz-sand-modified enamel (QSME) coatings can enhance the corrosion resistance of bare steel by a factor of 1000. Although the corrosion resistance of these coated plates diminishes with higher quartz sand content, the size of the sand particles has a negligible impact on corrosion behavior. This QSME coating is beneficial for extending the lifespan of civil infrastructure facing chloride-induced degradation. Orihel et al. [4] conducted a study on the properties and kinetic modeling of boride layers formed on Bohler K190 steel. Their research focused on the steel produced via powder metallurgy, which was then treated with the boronizing process. In the study, the maximum thickness of the boronized layers, the redistribution of elements within these layers, and the transition zone between the layers and the base steel were analyzed.

Wear resistance is a critical attribute for steels operating under heavy loads and in high-temperature environments. Luiz et al. [5] explored how different contact scenarios affect the frictional characteristics of Nb-stabilized AISI 430 stainless steel, known for its deep drawing quality. They conducted three types of tribological tests: pin-on-disk, bending under tension, and strip-tension, using hard metal (WC-12%Co) samples with varying surface finishes for both dry and lubricated conditions. They also examined how the strip’s texture and elongation affect formability. The findings indicated that friction, wear, lubricant performance, and hardness are heavily influenced by surface roughness and the type of friction test. These data can inform design guidelines to enhance productivity and product quality. Teng et al. [6] studied the high-temperature friction of 10Mn5 medium manganese steel under real hot stamping conditions using a high-temperature sliding-on-sheet-strip (SOSS) tribometer. They analyzed the oxide layer’s structure, the wear surface’s morphology, and the elemental composition. The study found that 10Mn5 steel had a lower average coefficient of friction than 22MnB5 steel, with both having an oxide layer, an alloying element-rich layer, and a matrix. The intact oxide layer of 10Mn5 steel provided superior wear protection, with wear primarily caused by abrasion and slight adhesion. The difference in wear mechanisms was attributed to the austenitizing temperatures, with 10Mn5 steel requiring temperatures about 100 °C lower than 22MnB5, reducing thermal stress and wear. Kyryliv et al. [7] investigated how different deformation modes during mechanical pulse treatment (MPT) affect the formation of nanocrystalline structures and wear resistance in 41Cr4 steel. They found that multidirectional deformation during MPT led to smaller grain sizes and increased surface layer depth and microhardness, enhancing wear resistance compared to unidirectional deformation. Cao et al. [8] examined the tribological properties of the 40Cr/GCr15 pair under unidirectional rotary and reciprocating dry sliding. They discovered that rotary sliding resulted in a more stable friction coefficient and superior wear resistance. The study concluded that the metamorphic structure and microhardness of the tribo-layer, influenced by sliding, are key determinants of tribological performance.

Wear simulation is proving to be a valuable tool in materials research. Hao et al. [9] explored the wear characteristics of a 3-D fractal rough surface, utilizing fractal theory and Hertz contact theory to understand how wear deformation depth correlates with real contact area. They developed models for calculating wear over time on both worn and unworn surfaces, providing a comprehensive view of how wear changes the surface topography. This research could guide the design and production of better friction pairs.

In addition, low-cycle fatigue (LCF) is a common failure mode for engineering components. Lv et al. [10] investigated the LCF behavior of a novel martensitic steel (22MnSi2CrMoNi) and maraging steel (00Ni18Co9Mo4Ti). They discovered that the presence of retained austenite and precipitated phases in the matrix can significantly enhance the fatigue life of these steels. These findings are crucial for improving the durability of steel components in cyclic loading conditions.

In addition to advancements in steel technology, the development of high-performance composite materials is a pivotal area of research, particularly as they are increasingly being used as alternatives to traditional metal components. For instance, long glass-fiber-reinforced polypropylene (LGFR-PP) composites with integrated stiffeners are becoming significant replacements for metal parts in the automotive industry, especially in the pursuit of vehicle weight reduction [11]. These materials not only offer similar performance characteristics, but also contribute to resource optimization, a key objective for materials scientists.