Investigation of the effects of silicon and manganese addition on wear and microstructure of iron-based hardfacing coatings

Hardfacing surface coatings have long been employed in industry as a critical engineering practice to extend the service life of machine components and to secure their continuous operation through repair and maintenance. This surface engineering technique is primarily intended to reduce overall maintenance costs by protecting machine elements from progressive forms of damage such as wear, erosion, and corrosion. In essence, it provides a barrier that prevents premature failure and allows machinery to maintain reliable performance even under harsh working conditions. Traditionally, many industrial components were manufactured directly from alloyed steels to achieve higher strength and wear resistance. However, in contemporary practice, it has become increasingly common to produce parts from relatively low-cost, non-alloyed base materials and then apply hardfacing coatings to the surface, thereby combining economic efficiency with superior surface properties. A wide range of alloy systems is currently available for hardfacing applications. Nickel-, cobalt-, and iron-based alloys dominate the field, each serving particular industrial requirements. Nickel- and cobalt-based hardfacing materials are well recognized for their excellent resistance to high-temperature degradation, cavitation, and severe wear environments. Nevertheless, their relatively high cost restricts their widespread use, confining them to specialized applications such as power generation, aerospace, and petrochemical processing, where extreme service conditions justify the expense. In contrast, iron-based alloys, with their favorable balance of cost and performance, have gained popularity across almost all industrial sectors. Their adaptability and affordability have made them the preferred choice for general-purpose hardfacing, particularly in industries such as mining, construction, and manufacturing. A remarkable feature of hardfacing technology is its compatibility with a broad spectrum of welding processes. Almost all welding methods can be adapted for use in surface coating applications, though the selection of the appropriate process depends largely on the characteristics of the base material, the type of alloy being deposited, and the surrounding service conditions. Among the most frequently employed methods are shielded metal arc welding (SMAW), gas metal arc welding (GMAW), and tungsten inert gas welding (TIG). Each process offers distinct advantages. For example, SMAW is widely used because of its simplicity and ability to deposit a variety of alloys, while TIG provides greater control and precision, making it suitable for applications where uniform microstructure and defect-free coatings are required. Ultimately, the choice of method is not arbitrary but is guided by a careful evaluation of metallurgical compatibility and economic feasibility. The widespread use of iron-based coatings is closely linked to their significant cost advantage. These coatings not only provide high levels of wear resistance but also ensure that equipment remains operational over longer intervals, thus minimizing downtime and unexpected failures. An additional benefit is that the uniform application of coatings results in improved performance consistency, reducing the likelihood of localized stress concentrations or weak points that could trigger premature damage. In practice, the correct selection of hardfacing material requires engineers to carefully assess operating conditions, such as the type of wear mechanism present, the exposure to corrosive media, and the mechanical stresses to which the surface will be subjected. By tailoring the alloy composition to these factors, it becomes possible to optimize coating performance for specific industrial environments. Hardfacing technology is not static; it continues to evolve as industries demand more efficient, durable, and sustainable solutions. Recent research has particularly emphasized the development of novel alloy compositions to improve hardness, wear resistance, and microstructural stability. Among the most notable advances is the incorporation of silicon and manganese as alloying elements in Fe-Cr-C-based coatings. These elements play a decisive role in modifying the microstructure by refining carbides and improving phase distribution, thereby enhancing both hardness and wear resistance. For instance, silicon contributes to solid solution strengthening and promotes the formation of desirable carbide phases, while manganese influences toughness and stabilizes the microstructural balance. Together, these additions can yield coatings that exhibit superior mechanical performance under demanding conditions. Equally important is the selection of the most appropriate deposition method. Even the best alloy system may fail to achieve its intended performance if the coating process introduces defects such as porosity, cracks, or uneven dilution with the substrate. Thus, engineers and materials scientists are increasingly focusing on optimizing process parameters in parallel with alloy design. This integrated approach ensures not only that the coatings achieve the desired hardness and wear resistance but also that they maintain their properties over extended service periods. In conclusion, hardfacing surface coatings represent a versatile and indispensable engineering solution to modern industrial challenges. They provide a means of reconciling the need for economic efficiency with the demand for high-performance materials. With continuing advances in alloy development and welding technology, hardfacing is poised to play an even greater role in enabling sustainable production, reducing maintenance costs, and extending the operational lifetimes of critical machinery. Ongoing innovations, particularly in the design of alloy systems containing elements such as silicon and manganese, demonstrate the dynamic and forward-looking nature of this field. As industries evolve, so too will the science and practice of hardfacing, ensuring its continued relevance in meeting the diverse needs of engineering applications. In this context, the present study investigates the effects of silicon and manganese additions on the wear resistance, hardness, and microstructure of Fe-Cr-C-based hardfacing coatings. The globally preferred shielded metal arc welding (SMAW) method was employed for the coating process. For alloying, ferrochrome, ferrosilicon, and ferromanganese were used, while rutile, calcite, potassium feldspar, and fluorspar minerals were included in the coating mixture to stabilize the arc. This mixture was extruded onto unalloyed S1-grade core wire using an extruder press to produce coated electrodes. The produced electrodes were then applied onto S355J2+N unalloyed substrate material using a GEKA RKM 650 welding machine under 200 A welding parameters. In the prepared specimens, chromium and carbon were kept constant at 32.00% and 4.50%, respectively. The specimens were grouped based on Si and Mn content and prepared metallographically. Their chemical compositions were analyzed according to TS EN ISO 15614-7 standards. Following one pass of hardfacing onto the substrate, the specimens were metallographically prepared, and the microhardness of the weld metal, heat-affected zone, and substrate was measured under a 1 kg load. Results showed that increasing alloying element content led to higher hardness values. The lowest average hardness was measured as 635 HV1 in the Si0Mn0 sample, while the highest value of 866 HV1 was recorded in the Si3Mn3 sample. Among the grouped specimens, a significant increase in hardness was observed with increasing Mn content when Si content was low. However, as the Si content increased, the influence of Mn on hardness decreased. Wear resistance tests were conducted in accordance with ASTM G133 standards using a reciprocating sliding configuration at 25 °C, 30% relative humidity, under a 5 N load, and for a total sliding distance of 100 m. The wear surfaces were examined by SEM and compared across the samples. Abrasive, adhesive, and oxidative wear mechanisms were observed, while some specimens also exhibited delamination and microcracking. Additionally, the microstructures of the test specimens were investigated and compared using optical microscopy and SEM. The microstructure analysis revealed a dendritic γ-Fe matrix with lamellar carbides of Cr7C3, Fe7C3, Fe5C2, and Cr2Fe14C formed between dendrite arms. Notably, Cr2Fe14C was detected only in specimens containing manganese. The experimental results demonstrated that mechanical properties of the coatings improved with increasing alloy content and that homogeneous phase distributions were achieved.