ROLLED ALLOYS Heat and Corrosion Resistant Alloy Specialists

This chart is intended as guidance for what alloys might be tested or used in a given environment. It must NOT be used as the sole basis for alloy selection, or as a substitute for competent engineering support. Alloy selection for high temperature equipment should be based on experience with similar environments and extensive testing under the exact service conditions of interest. Some points to consider: A major cause of distortion and cracking in elevated temperature service is the effect of thermal expansion. Total expansion in the range of 3/16 to 1/4" per foot, from room temperature to 1800 °F, is common. It is important to allow this expansion to occur freely. Welds should be completely penetrated, as lack of fusion may start cracks in cyclic service. When thermal shock or fatigue is involved, design and weldment quality may override the effect of alloy selection on performance. With respect to corrosion, high temperature corrosion rates are not uniform. Hot corrosion test data, most particularly sulfidation rates, can not be reliably extrapolated.

Alloy Performance Guide Resistance To Environment

CONDITION Not Suggested Good Better Best STRENGTH 446 600 310 309, 321 RA153MA RA85H RA300 RA333 601, RA353MA RA253MA RA800H/AT THERMAL SHOCK (a) 446 RA800H/AT 310 309 RA153MA RA253MA RA353MA, 601, 600 RA333 RA85H RA330 OXIDATION - RA153MA 309 RA800H/AT 446 RA330, 600 310 RA85H RA333, RA353MA 601 RA253MA CARBURIZATION 446 RA153MA 321 RA253MA 310 309 RA800H/AT RA85H RA330 RA333 600 601 RA353MA OXIDIZING SULFUR (SO2, SO3) 600 601 RA330 RA153MA 321 RA800H/AT RA253MA RA353MA, RA333 446 310 RA85H 309 REDUCING SULFUR (H2S) (b) RA353MA, RA330 RA253MA RA333 601, RA800H/AT 600 347 309, RA85H 556 310 446 HOT HCI GAS (above the dew point) 446 RA333 RA330 RA353MA 601 600 200 MOLTEN METALS (c) Cu(d), Zn, Mg 600 316 (Zinc) AL-6XN (Zinc) 309, 310 RA253MA RA85H 430 446 E-BRITE

(a) Good thermal shock or fatigue strength requires both fine grain size and hot tensile strength. Materials which are grain-coarsened to maximize creep-rupture strength do so at the expense of thermal fatigue resistance. (c) Molten aluminum quickly dissolves all commercial alloys. (b) Resistance to sulfur (H25) in high temperature reducing atmospheres depends upon relatively high chromium and low nickel contents. RA85H is an exception in environments where both carbon and sulfur are present. Because of its very high silicon content, RA8SH resists the carburization which often precedes failure by sulfidation. (d) Only the ferritic alloys such as 430, 446, and E-BRITE,® withstand copper. All austenitics are rapidly attacked.