Research on Wear-Resistant Materials and Their Applications

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0061106 Tang Haiyan, Institute of Foundry and Wear-Resistant Materials, Xi’an Jiaotong University. The institute has been engaged in research on wear-resistant materials since the late 1970s; it has completed numerous research projects, including those under the **”Seventh Five-Year Plan”** for scientific and technological development, projects funded by the Natural Science Foundation, projects supported by the Education Commission’s doctoral program funds, as well as initiatives for scientific and technological development through cooperation between factories and universities, along with projects aimed at solving problems faced by enterprises and carrying out technical upgrades. The application fields involved include industries such as metallurgy, power generation, building materials, chemicals, and mining. Its wear conditions mainly include: normal-temperature abrasive wear, impact abrasive wear; high-temperature abrasive wear; corrosive abrasive wear, etc. Based on these operating conditions, the materials that have been developed and refined over the past 20 years and are now used in products include chromium-based wear-resistant cast irons, martensite-bainite ductile iron, modified high-manganese steels, low-alloy wear-resistant steels, particle-reinforced metal matrix surface composites, and non-metal matrix composites. 1. Chromium-based anti-wear cast irons 1.1 High-chromium cast iron grinding balls and liners This project is part of the “Seventh Five-Year Plan” science and technology research initiative. The grinding balls and liner plates in ball mills are components that are used in large quantities for grinding. Using high-chromium cast iron for these components can significantly reduce the consumption of grinding balls, improve grinding efficiency, decrease the number of downtime periods, and lower energy consumption. They belong to the high-quality ball and liner materials that are popular in the world today. This project is applied to cement ball mills, and the target for improving the performance of the grinding balls (to reach a level close to that of foreign countries) is: a wear rate of 20 J/cm2. It is suitable for applications that involve certain levels of impact and require materials with high wear resistance, such as the linings of large ball mills. Currently, this material is used for the linings of 5000mm ball mills in the Jiangyou Power Plant’s French-made units; it has been in operation for nearly 4 years, and its expected service life is 6 years. It holds promise as a replacement for the original French-made high-manganese steel linings. 5 Ceramic particle-reinforced metal matrix surface composites are used in many wear-resistant components in industries such as electricity, metallurgy, mineral processing, and chemicals. These components must not only withstand wear from the materials they handle, but also resist severe corrosion from various media (such as the flow-through components in acid-resistant pumps used in chemical plants), as well as oxidation in high-temperature environments (such as nozzles used in power plant boilers). Under such severe operating conditions, metal anti-wear materials cannot meet the requirements. For example, heat-resistant steels or stainless steels possess good resistance to high-temperature oxidation or corrosion, but both have poor resistance to abrasive wear. Although high-chromium cast iron exhibits excellent resistance to abrasive wear, its high-temperature oxidation resistance and corrosion resistance are poor. To this end, research on surface composite materials has been carried out in recent years. Taking advantage of the high hardness and high chemical stability of ceramic particles (Al2O3, WC), these particles are bonded to the locally worn surfaces of stainless steel or heat-resistant steel components using the investment casting method, thereby overcoming the disadvantages of the conventional full-composite casting process, such as its complexity and the unnecessary waste of material. This research was supported by the Shaanxi Province Fund, the Scientific Research Fund of Xi’an Jiaotong University, and the Yunnan Provincial Science and Technology Commission. 5.1 WC particle-reinforced ductile iron matrix composites The objective of this study is to address the issues of low wear resistance and short service life of the flow-through components in the impurity pumps manufactured by Yunnan Yunxi Mining Company. The medium under its operating conditions is weakly alkaline; therefore, ductile iron was chosen as the matrix for the composite material. The microstructure of the resulting composite is shown in Figure 4. According to laboratory tests on abrasive wear using a three-body grinder at room temperature, the results show that its wear resistance is 12.5 times that of high-chromium cast iron. The casting process issues in this study have been largely resolved, allowing for trial production of the parts. Laser quenching of the mold surface is used to strengthen the wear-prone areas of casting and stamping molds, thereby significantly improving the wear resistance of these areas. Since laser quenching only increases the strength and hardness of the material’s surface layer without affecting the matrix structure, it not only enables very high hardness to be achieved but also helps to overcome the deformation and reduced plasticity resulting from full-quenching of the mold, thereby extending its service life by 1 to 2 times.