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HAYNES® Alloys

Oxidation Resistance

HAYNES® 25 alloy exhibits good resistance to both air and combustion gas oxidizing environments, and can be used for long-term continuous exposure at temperatures up to 1800°F (980°C). For exposures of short duration, 25 alloy can be used at higher temperatures. Applications for which oxidation resistance is a serious consideration normally call for newer, more capable materials such as 230® alloy or HAYNES 188 alloy. This is particularly important at temperatures above 1800°F (980°C).

Comparative Burner Rig Oxidation Resistance
1000 Hour Exposure at 1800°F (980°C), 30 minute Cycles

Alloy Metal Loss Average Metal Affected Maximum Metal Affected
mils μm mils μm mils μm
188 1.1 28 3.2 81 3.9 99
230® 2.8 71 5.6 142 6.4 163
617 2.4 61 5.7 145 6.9 175
625 3.7 94 6.0 152 6.6 168
X 4.3 109 7.3 185 8.0 203
25 7.8 198 9.8 249 10.3 262
310SS 16.0 406 18.3 465 19.5 495
800H 22.9 582 Internal oxidation through thickness

Comparative Burner Rig Oxidation Resistance at 2000°F (1095°C) for 500 Hours

Alloy Average Metal Loss per Side Maximum Metal Affected
mils µm mils µm
214 1.2 30.5 1.8 45.7
230® 7.1 180.3 11.8 299.7
188 10.9 276.9 14.1 358.1
X 11.6 294.6 15.1 383.5
25 > 25* >635* - -

*25 mils (635 µm) in 165 hours

Oxidation Test Parameters

Burner rig oxidation tests were conducted by exposing samples 3/8 in. x 2.5 in. x thickness (9 mm x 64 mm x thickness), in a rotating holder, to products of combustion of No. 2 fuel oil burned at a ratio of air to fuel of about 50:1. (Gas velocity was about 0.3 mach). Samples were automatically removed from the gas stream every 30 minutes and fancooled to near ambient temperature and then reinserted into the flame tunnel.

Comparative Oxidation Resistance in Flowing Air*

Alloy 1800°F (980°C) 2000°F (1095°C) 2100°F (1150°C)
Average Metal Affected Metal Loss Average Metal Affected Metal Loss Average Metal Affected Metal Loss
mils μm mils μm mils μm mils μm mils μm mils μm
188 1.1 28 0.1 3 3.7 94 0.5 13 10.7 272 8.6 218
230® 1.5 38 0.2 5 3.3 84 0.5 13 4.4 112 1.2 30
25 2.0 51 0.3 8 10.2 259 9.2 234 10.7 272 8.2 208
X 1.5 38 0.2 5 4.4 112 1.3 33 6.1 115 3.6 91
625 1.9 48 0.4 10 7.8 198 3.5 89 20.2 513 18.3 465
617 2.0 51 0.3 8 3.8 97 0.6 15 5.2 132 1 25
800HT 4.1 104 0.5 13 11.6 295 7.6 193 15.0 381 11 279

*Flowing air at a velocity of 7.0 ft/min (213.4 cm/min) past the samples. Samples cycled to room temperature once per week.
**Average Metal Affected = Metal Loss + Average Internal Penetration

Schematic Representation of Metallographic Technique Used for Evaluating Environmental Tests


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