In many industrial sectors, piping systems face harsh operating environments, with frequent problems such as wear and corrosion, severely impacting pipeline life and system stability. Ceramic steel pipes lined with SiC special ceramics, with their superior performance, are an ideal solution to these problems, revolutionizing industrial piping applications.

I. Material Properties of SiC Ceramic Linings

(I) High Hardness and Excellent Wear Resistance

SiC ceramics boast a Mohs hardness of 9.5, second only to diamond and the highest among all oxides. Its microhardness, HV 2500-3000, provides pipes with unparalleled wear resistance. In mining, power generation, metallurgy, and other applications involving the transport of high-hardness granular materials, such as tailings slurries containing large amounts of quartz sand, conventional pipes suffer from severe wear. However, SiC ceramic-lined pipes effectively resist material erosion, significantly extending their service life and reducing wear by over 90% compared to ordinary steel pipes.

(2) Excellent Corrosion Resistance

From a chemical perspective, SiC is composed of silicon (Si) and carbon (C) forming a stable three-dimensional network through high-energy covalent bonds (bond energy 318 kJ/mol). Its chemical stability far exceeds that of metals (metallic bond energy 50-200 kJ/mol). Its surface energy is as low as 25-40 mJ/m² (stainless steel has a surface energy of approximately 1000 mJ/m²), making it difficult for corrosive media to adhere to and penetrate. Whether exposed to strong acids (such as sulfuric acid and hydrochloric acid) and strong bases (such as sodium hydroxide) in the chemical industry, or high-temperature molten salts and corrosive gases in the metallurgical industry, SiC ceramic linings remain stable. Its corrosion resistance is over 10 times stronger than that of stainless steel, effectively preventing pipeline leaks due to corrosion and ensuring production safety and continuity.

(3) Excellent High-Temperature Resistance

SiC ceramics perform exceptionally well in high-temperature environments. They can operate stably and for long periods of time within a temperature range of -50°C to 1600°C. When the temperature exceeds 800°C, an oxidation reaction forms a dense SiO₂ glass layer on the surface (reaction formula: SiC + 2O₂ → SiO₂ + CO₂↑). The thickness is approximately 1-5μm. This oxide film acts as a "thermal shield," effectively blocking further oxygen diffusion and reducing the oxidation rate (<0.01 mm/year, according to ASTM G54 testing). It also maintains the stability of the ceramic structure, ensuring the normal operation of the pipeline under high-temperature conditions, meeting the requirements of high-temperature industries such as steel smelting and glass manufacturing.

(IV) High Thermal Conductivity and Low Thermal Expansion Coefficient

SiC ceramics have a thermal conductivity of 120-200 W/(m・K), enabling rapid heat transfer, uniform temperature distribution within the pipeline, and preventing localized overheating. At the same time, its coefficient of thermal expansion is approximately 4.5×10⁻⁶/K, only about half that of steel. This gives the pipe excellent thermal shock resistance, allowing it to withstand frequent rapid cooling and heating cycles. It is less susceptible to cracking and spalling due to thermal stress during drastic temperature fluctuations, making it suitable for processes subject to large temperature fluctuations, such as the startup and shutdown of power plant boilers.

II. Structural Design of SiC Linings for Ceramic Steel Pipes

(I) Composite Structure

The SiC linings for ceramic steel pipes utilize a composite structure consisting of a "SiC ceramic layer - transition layer - steel matrix." The inner SiC ceramic layer directly exposes itself to material erosion and corrosion, leveraging its wear and corrosion resistance. The intermediate transition layer is typically made of materials such as cermets, whose composition and structure combine the characteristics of both ceramics and metals. This effectively buffers the stress generated by the difference in thermal expansion coefficients between the ceramic layer and the steel substrate, strengthening the bond between the two and preventing the ceramic layer from falling off due to temperature fluctuations or mechanical impact. The outer steel substrate provides the required strength and toughness for the pipeline, withstanding external pressure and the mechanical forces during installation and transportation, ensuring the overall structural stability of the pipeline.

(II) Manufacturing Process Ensures Structural Stability

The manufacturing processes for SiC ceramic-lined pipes are diverse and sophisticated. For example, reaction sintering involves first contacting a carbon-containing blank with molten silicon. The silicon and carbon react to form SiC, which fills the pores and forms a solid ceramic layer. This method is cost-effective and suitable for manufacturing large-scale and complex-shaped components. Pressureless sintering utilizes high-purity submicron silicon carbide powder, added with sintering aids such as boron and carbon, and sintered in an inert atmosphere at temperatures above 2100°C. This produces a nearly fully dense, microstructurally uniform sintered body, significantly improving ceramic performance. During the composite process, hot pressing and hot isostatic pressing are used to tightly bond the layers, ensuring structural integrity and stability.

III. Application Areas and Advantages

(I) Mining Industry

In mining, tailings conveying pipelines are subject to long-term erosion and wear from high-concentration, high-hardness slurries. Using SiC ceramic-lined pipes significantly reduces the wear rate, extending the service life of the pipes to 5-10 times that of ordinary steel pipes, reducing the frequency of pipe replacements and maintenance costs, and ensuring continuous mine production. Furthermore, its corrosion resistance can withstand the potential presence of acidic substances in the slurry, preventing corrosion and perforation of the pipes and mitigating environmental pollution risks.

(II) Power Industry

Pulverized coal transportation: In power plants, pulverized coal flows at high speeds within the pipes, causing severe wear and tear on the pipe walls. SiC ceramic linings, with their high hardness and smooth surface, effectively reduce wear and tear on pipes caused by pulverized coal, minimizing leaks and repairs caused by wear, improving pulverized coal conveying efficiency, and ensuring a stable coal supply to power plant boilers.

Ash and slag discharge: Ash and slag contain a large number of sharp particles and are somewhat corrosive. SiC ceramic-lined pipes can withstand erosion and corrosion from ash and slag, ensuring the long-term stable operation of the ash and slag discharge system, reducing equipment failure rates, and improving the overall economic efficiency of power plant operations.

(III) Metallurgical Industry

Blast furnace coal injection: The high temperature and high velocity of pulverized coal gas flow causes significant wear and tear on coal injection pipes. SiC ceramic-lined pipes maintain high hardness and wear resistance in high-temperature environments, ensuring stable coal conveying, ensuring smooth blast furnace ironmaking, reducing blast furnace shutdowns due to pipe wear, and improving production efficiency.

Slag conveying: Slag is hot, hard, and corrosive, making it difficult for ordinary pipes to withstand it. The high temperature, wear, and corrosion resistance of SiC ceramic-lined pipes make them an ideal choice for slag conveying, effectively extending pipe service life and reducing production costs. (IV) Chemical Industry

In chemical production, pipelines often transport corrosive media such as strong acids, strong bases, and organic solvents. The chemical stability of SiC ceramic linings allows them to withstand the erosion of these media, preventing pipeline corrosion and leakage, ensuring chemical production safety and reducing production losses caused by pipeline replacement. SiC ceramic linings are widely used in the chlor-alkali industry, fertilizer production, petrochemicals, and other fields.