High-temperature heat exchangers must withstand extreme thermal conditions, corrosion, and mechanical stress. Therefore, the materials used are carefully selected for their thermal stability, oxidation resistance, and mechanical strength. Common materials include:
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Stainless Steel (e.g., 304, 316, 310, 321)
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Good corrosion resistance and mechanical strength
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Suitable for temperatures up to ~800°C (depending on the grade)
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Inconel (e.g., Inconel 600, 625, 718)
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A nickel-chromium alloy with excellent resistance to oxidation and creep at temperatures up to ~1000°C
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Common in aerospace, chemical, and power plant applications
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Hastelloy
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Nickel-molybdenum alloys known for corrosion resistance under severe conditions
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Useful in high-temperature, chemically aggressive environments
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Titanium and Titanium Alloys
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Excellent corrosion resistance, moderate high-temperature performance (~600°C)
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Often used in heat exchangers exposed to seawater or aggressive chemicals
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Ceramics (e.g., Silicon Carbide, Alumina)
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Extremely high temperature resistance (>1200°C)
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Brittle, but ideal for specialized high-temp gas heat exchangers
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Carbon Steel
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Cost-effective and strong, but less resistant to corrosion and oxidation
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Typically used in applications below ~425°C
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Aluminum Oxide-Coated Metals
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Coatings help extend the temperature range and protect from oxidation
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High-temperature heat exchangers must survive thermal stress, oxidation, and sometimes corrosive flue gas. The most common structural materials are stainless steels such as 304 and 316L, which cover many exhaust and process duties up to several hundred degrees Celsius. For more demanding service, 310S and other high-nickel alloys resist scaling and creep at elevated temperatures and extend service life.
In air-to-air plate recovery, aluminum is widely used but is limited by its lower temperature ceiling, so stainless or special alloys take over when inlet streams exceed roughly 200 to 250 degrees Celsius. Coatings and surface treatments can extend life in mildly corrosive streams, though they cannot replace a properly rated base alloy in severe duty.
Material choice is a trade-off between cost, temperature rating, and corrosion resistance. A flue-gas application with sulfur or chlorides needs a grade chosen against the actual chemistry, not a generic "stainless" label. Buyers should ask for the material certificate and the design temperature envelope before approving the order.
For sensible air-to-air recovery in clean, hot streams, a well-specified stainless plate core often delivers the best balance of life and price. Where the exhaust is mildly corrosive, a protective coating on a standard grade may be enough. Always match the alloy to the worst-case condition rather than the average, because localized attack at a joint or edge is what usually ends a core's service life.