At higher temperatures, most chemical processes speed up and power generation efficiency increases. But can the material withstand high temperatures? In practice, the highest temperatures in many processes are limited by material suitability. Nickel can solve the issue.
When selecting materials for high-temperature applications, the 4 most important properties are strength, sustained stability, limited environmental response, and the convenience of equipment production.
As the temperature increases, the strength of the metal decreases. At higher temperatures, many types of steel have a strength higher than 300 series stainless steel. Stainless steel performs better than most of them at 540 C. However, nickel-containing alloys perform well at temperatures above 650 C. However, creep strength or creep fracture strength becomes the most important property at temperatures above 540 C.
Metallurgical properties change over time at high temperatures. The most interesting thing is when the metal forms a hard and brittle phase when the material becomes as fragile as glass. Nickel slows down the formation of these phases, while nickel-chromium-iron alloys containing at least 33 percent Ni are not affected.
Metals react with the environment at very high temperatures. It oxidizes in the air. Alloys with chromium and aluminum provide additional protection. Reducing environments containing carbon monoxide, Ni, and silicon help to reduce carbonization. New alloys that are adapted to the most demanding environments are being developed and tested when rapid carbonization (called metal dust) occurs, and all of these alloys have a high Ni level. Finally, related equipment needs to be manufactured, involving metal shaping and welding, where nickel-containing stainless steel and Ni alloy perform excellently.
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The converter tube is made of cast nickel alloy, It can be used for hundreds of thousands of hours in a carbonized environment at 800-1000 degrees C. They can be used with steam and hydrocarbons to generate hydrogen.
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The radiation tube heats the furnace indirectly. Various nickel alloys have been used with temperatures as high as 1150 C, while metals can tolerate temperatures as high as 1200 C.
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The heat treatment basket fixes the parts in the heat treatment furnace. The nickel-containing alloy selected depends on whether the atmosphere is oxidative or reducing. They generally operate more stably. |
