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 |
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 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
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