Alloy 25

Alloy 25 was developed for the steam and flue-gas side of an advanced coal-fired boiler, and its published performance reflects that. Air oxidation testing at 650°C and 750°C for up to 3000 hours shows very low mass change, and oxidation resistance in aqueous steam is very good at 600°C over 500 hours and at 700°C over 1000 hours. Hot corrosion resistance in coal-ash environments is very good, which is the mechanism that limits life in pulverised-coal superheaters. The 22.5% chromium supports both steam oxidation and hot corrosion resistance, while roughly 25% nickel together with the high nitrogen content keeps the face-centred-cubic austenitic structure stable in long-term service. Creep strength is very high, and the austenitic structure gives very good impact strength including at cryogenic temperatures.

The S alloy numbers are brand designations, not UNS numbers, and they do not map onto the alloy numbers used elsewhere in this catalogue. Alloy 41 in this family is UNS N08825 — the alloy sold generically as 825 — not the Rene 41 superalloy. Alloy 60 is UNS N06625, which is alloy 625, while Alloy 70 is UNS N06600, which is alloy 600. Alloy 31HT is UNS N08810/N08811, the 800H and 800HT chemistry. Always confirm the UNS number rather than ordering against the brand number alone; the S Alloys cross-reference table sets out the full mapping.

Sanicro is a trademark of Alleima, the former Sandvik Materials Technology business. Exotic Alloy is an independent manufacturer and is not affiliated with or endorsed by Alleima or Sandvik; the designation is used here solely to identify the alloy chemistry, which is defined by the UNS and EN numbers given above.