RA 253 MA Alloy – Still Growing, After All These Years

While RA330® has been a solid alloy choice for carburizing, nitriding and many other heat treating applications, stainless alloys such as 304H, 309 and 310 are also used extensively in industrial heating applications.

Such non-heat treating applications include recuperators, burner nozzles, tube hangers, tube shields, combustion chambers, reverse thermal oxidizers, fans, dampers and cyclones. The range of industrial heating applications is extensive.

Although the 253 MA alloy has been in service for many years, many users are just now discovering the advantages this alloy offers over other heat resistant stainless steels.  The main differences between RA 253 MA and both 309 and 310 stainless steel are the additions of cerium and nitrogen and an increased silicon content. RA 253 MA actually also has a lower alloy content of nickel and chromium making it less susceptible to fluctuating commodity prices.  While the alloy has less chromium than 309, its oxidation resistance is comparable to 310 at temperatures up to 2000°F.

The micro alloy addition of cerium helps improve oxidation resistance by strengthening the oxide adhesion. Silicon additions provide a secondary oxide scale below the primary chromium oxide layer that gives RA 253 MA good oxidation resistance up to 2000°F which is better than 309.  Due to higher controlled carbon levels and nitrogen additions, the creep strength of RA 253 MA is more than twice that of both 309 and 310 stainless at temperatures of 1600°F through 2000°F.

The alloy is readily weldable and uses matching consumables.  RA 253 MA is also available in a wide range of product forms including sheet, plate, bar and pipe.  Rolled Alloys has continued to add to the range of sizes available, adding to its increasing popularity.

While the alloy has been more widely used for industrial heating applications, its use in the heat treating industry is also on the rise.  RA330 is still the alloy of choice for carburizing and nitriding atmospheres, but in air atmosphere processes where the temperatures remain below 2000°F, RA 253 MA should get close scrutiny.  The alloy has also shown excellent performance for heat treating situations above 2000°F under vacuum.