How do steel auto parts cope with the challenges of high-temperature oxidation?
Publish Time: 2025-08-27
During vehicle operation, steel auto parts, such as engine peripheral components, exhaust systems, turbocharger brackets, clutch pressure plates, and brake system components, are exposed to high temperatures for extended periods of time. Operating temperatures often exceed 300°C, and in some cases, even exceed 800°C. Under such high temperatures, steel easily reacts chemically with oxygen in the air, forming iron oxide. This can lead to surface flaking, thickness loss, and decreased strength. In severe cases, it can even cause structural failure. Therefore, effectively addressing the challenges of high-temperature oxidation is a key technical challenge in ensuring automotive safety and durability.1. Mechanism and Hazards of High-Temperature OxidationHigh-temperature oxidation refers to the process by which metals react with oxygen at high temperatures to form metal oxides. For ordinary carbon steel, the oxidation rate increases dramatically when temperatures exceed 400°C. The resulting oxide crust is loose and easily detached, failing to form a protective layer and instead accelerating further oxidation of the metal underneath. This continuous oxidation not only weakens the load-bearing capacity of components but can also increase clearances, weaken seals, and even cause fractures or malfunctions. Furthermore, high-temperature oxidation is often accompanied by phenomena such as thermal fatigue and creep, further exacerbating material degradation. For example, exhaust manifolds undergo repeated expansion and contraction during hot and cold cycles, causing the oxide layer to crack and flake, exposing new metal surfaces for further oxidation, creating a vicious cycle.2. Selecting High-Temperature-Resistant Alloy Steel: Improving Resistance from the SourceThe most fundamental approach to combating high-temperature oxidation is to select steel with excellent oxidation resistance. Currently, the automotive industry widely uses the following types of high-temperature-resistant steel:Heat-resistant stainless steel: Ferritic stainless steels such as 409L and 436L contain elements such as chromium (Cr) and aluminum (Al). They form a dense protective film of chromium oxide (Cr₂O₃) or aluminum oxide (Al₂O₃) on their surfaces, effectively preventing oxygen diffusion and significantly slowing the oxidation rate. These materials are commonly used in high-temperature components such as exhaust manifolds and mufflers.High-Silicon, High-Aluminum Steel: By adding silicon (Si) and aluminum (Al), a stable SiO₂ or Al₂O₃ oxide layer forms at high temperatures, providing excellent resistance to oxidation and thermal fatigue.Nickel-Based Alloys: In extremely high-temperature environments (such as turbocharger housings), some high-end vehicles use nickel-based high-temperature alloys. These alloys offer oxidation resistance temperatures exceeding 1000°C, but are relatively expensive and are primarily used in high-performance or luxury vehicles.3. Surface Treatment Technology: Building a Protective BarrierEven with ordinary steel, its resistance to high-temperature oxidation can be enhanced through advanced surface treatment technologies:Hot-Dip Aluminizing: Immersing steel parts in molten aluminum creates an aluminum-iron alloy layer on the surface. This layer transforms into a dense Al₂O₃ oxide film at high temperatures, providing long-term protection and widely used in exhaust systems.Al-Si Coating: Aluminum-Si alloy coatings are applied to steel surfaces through hot-dip or spraying, offering both oxidation and corrosion resistance. They are commonly used in components such as engine mounts and heat shields.Ceramic Coating: Using plasma spray or arc spray technology, ceramic materials such as zirconium oxide and aluminum oxide are applied to metal surfaces to create a high-temperature-resistant, low-thermal-conductivity insulation layer. This layer prevents oxidation and reduces the heat load on surrounding components.Blackening and phosphating: Although primarily used for low- to medium-temperature protection, they can also delay initial oxidation to a certain extent when used in conjunction with high-temperature grease or sealant.4. Structural Design Optimization: Reducing Thermal Stress and Exposed AreaReasonable structural design can also effectively reduce the risk of high-temperature oxidation. For example, exhaust systems utilize a double-walled pipe structure, creating an air insulation layer in the middle to reduce the outer wall temperature. Heat dissipation holes or heat shields are installed in high-temperature areas to guide airflow and cool the air. Sharp corners and stress concentration areas are avoided to reduce the acceleration of oxidation caused by thermal fatigue cracking. Furthermore, optimizing cooling systems and thermal management strategies, such as adding deflectors and wrapping high-temperature components with insulation, can effectively reduce the actual operating temperature of steel components, thereby reducing the degree of oxidation.5. Regular Maintenance and Inspection: Extending Service LifeFor vehicles already in service, regular inspection of steel parts in high-temperature areas for oxidation is crucial. Any severe spalling, cracking, or wall thinning should be promptly replaced to avoid potential safety incidents. Maintaining a clean engine compartment to prevent corrosion from oil, salt, and other factors also helps extend component life.For steel auto parts to meet the challenges of high-temperature oxidation, coordinated efforts are required in material selection, surface treatment, structural design, and maintenance management. As automotive powertrains evolve toward higher efficiency and higher temperatures, high-temperature oxidation resistance technology will continue to advance.
