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Which alloy offers the highest oxidation resistance?

austenitic stainless steels corrosion resistance

Hastelloy alloys are known for offering supreme corrosion resistance and elevated temperature strength.

Hastelloy B is used in several high temperature applications including forged supercharger blades, engine rings and rocket nozzles.

Hastelloy B3 is made for service in corrosion resistant, high temperature and high strength applications. An inclusion of chromium is beneficial for high temperature oxidation and oxidizing acid solutions. High concentration of molybdenum offers good resistance to reducing acids.

High temperature applications of Hastelloy C include nozzle skirts, vanes and aircrafts. Advanced grades of Hastelloy wires made from group of Hastelloy C alloys such as Hastelloy C-276, Hastelloy C-4, Hastelloy C22, Hastelloy C2000 etc are basically used in multi-purpose applications for offering great resistance to strong oxidizing and reducing acids.

Hastelloy alloys are remarked as predecessors to the advanced solid-solution strengthened super alloys. After the development of Hastelloy B-3 and Hastelloy C2000 alloys, there followed a period of considerably limited alloy development activity without patent application filings for length of eight years.

Hastelloy X is one of the commonly used sheet materials in the gas turbine plants. Alloy X discovered by Howard R. Spendelw and Walter Crafts, has excellent creep-rupture strength, particularly for its low concentration and high concentration of iron. Although what eventually makes Hastelloy X alloy different from others is its supreme oxidation resistance. These characteristics paired with supreme fabricability, permitted alloy X to be specified in the diverse gas turbine applications, combustors transition ducts, spray bars, flameholders and several afterburner parts. For over six decades, Hastelloy X is one of the most used super alloys in the gas turbine engines.

Haynes 214 alloy– Most of wrought high temperature alloys have their oxidation resistance from the development of a security chromia surface oxide layer. While it offers sufficient security, surface coatings are applied for extra oxidation resistance. These feature Nickel-Chromium-Aluminum  coatings called because of their chemistry. These layers secure through the development of an alumina surface oxide layer that offers higher protection than chromia. Advanced concept of Haynes 214 was to make a wrought, fabricable alloy that would take benefit of this kind of oxidation resistance. To make this real, it was essential to decrease the magnitude of yttrium as it was discovered to result in grain boundary oxidation and incipient melting when available in very high concentration.

Another essential factor of this invention was to control the magnitude of gamma prime phase by limiting the magnitude of aluminum to around 4.5% and inclusion of about 3% iron that decreases gamma prime solvus and its embrittling properties. The consequence of the development program was an achievement and Haynes 214 is popular as the best oxidation resistant alloy. It can be fabricated and welded however it is essential to be careful to prevent major effects of gamma prime development. The average strength of the alloy at the elevated temperatures limits the applications where strength is not as crucial. Gas turbine applications for Haynes alloy include honeycomb seals and combustor splash plates. It is used in burner assemblies, furnace hardware, refractory anchors and fume hoods.