High-temperature Alloys for Thermocouple Protection Tubes Tech Brief
Thermocouple Protection Tubes and Thermowells
When it comes to finding a thermocouple protection tube material to withstand aggressive environments or high stress at elevated temperatures, turn to HAYNES® alloys for the long-term performance that means a cost-effective solution. A full range of alloys is available to solve those problems which force stainless steels, nickel-chromium alloys, and iron-nickel-chromium alloys into an “early retirement”. Whether the application is in a chemical waste incinerator, a forging furnace, a brick kiln or a gas turbine – there’s a HAYNES® alloy suited to the application. Look to 214®, 230®, or 556® alloys for all your T/C tube needs.
Stress Rupture 1800°F/2.0 ksi
(980°C / 14 MPa)
Stress Rupture Life (Hours)
1800°F (980°C) Sulfidation Resistance
Average Metal Affected, µm*
Average Metal Affected, Mils*
215 hour exposures in H2S-bearing reducing environment test gas at 1800°F (980°C).
*Wastage + internal attack.
Resistance to Combustion Gas Environment 2000°F (1095°C) for 500 Hours
Alloy | Metal Loss | Maximum Metal Affected** | ||
– | mils | µm | mils | µm |
214® | 0.5 | 13 | 1.8 | 46 |
230® | 2.2 | 56 | 5.7 | 145 |
RA330® | 10.9 | 277 | 13.6 | 345 |
600 | 17.2 | 437 | 20.7 | 526 |
Type 310 | 21.2 | 538 | 24.1 | 612 |
601 | 10.7 | 272 | >24.0 | >610 |
Nominal Composition wt. %
Alloy | Ni | Fe | Co | Cr | Mo | W | Si | Mn | Al | C | Other |
230® | Balance | 3 max. | 5 max. | 22 | 2 | 14 | 0.4 | 0.5 | 0.3 | 0.10 | 0.015B, 0.01La |
214® | Balance | 3 | 2 max. | 16 | – | – | 0.2 max. | 0.5 max. | 4.5 | 0.04 | 0.01Y, 0.1 max.Zr |
556® | 20 | Balance | 18 | 22 | 3 | 2.5 | 0.4 | 1 | 0.2 | 0.10 | 0.2N, 0.6Ta, 0.02La, 0.017Zr |
Product Description
HAYNES® 230® alloy combines excellent high-temperature strength, outstanding resistance to oxidizing environments up to 2100°F (1150°C) for prolonged exposures, premier resistance to nitriding environments, and excellent long-term thermal stability. It is readily fabricated and formed. Other attractive features include lower thermal expansion characteristics than most high-temperature alloys, and a pronounced resistance to grain coarsening with prolonged exposure to high-temperatures.
HAYNES® 556® alloy combines effective resistance to sulfidizing, carburizing and chlorine-bearing environments at high temperatures with good oxidation resistance, fabricability, and excellent high-temperature strength. It has also been found to resist corrosion by molten chloride salts, moltenzinc, and other aggressive environments.
HAYNES® 214® alloy is the most oxidation-resistant, carburization-resistant, and chlorination-resistant alloy available as a fabricable material. Its effective use temperature limit is in excess of 2200°F (1204°C) for prolonged exposure, and up to 2400°F (1316°C) for shorter exposures.
Typical Tensile Properties (Plate)
Test Temperature | Ultimate Tensile Strength | 0.2% Yield Strength | Elongation | |||||||
ksi | ksi | % | ||||||||
°F | °C | 230® | 556® | 214® | 230® | 556® | 214® | 230® | 556® | 214® |
70 | 21 | 124.9 | 118.1 | 145.0 | 56.9 | 59.5 | 82.0 | 48 | 48 | 37 |
1200 | 649 | 97.2 | 85.4 | 120.0 | 39.0 | 32.8 | 85.0 | 55 | 52 | 31 |
1400 | 760 | 84.9 | 68.5 | 102.0 | 41.2 | 32.0 | 79.0 | 46 | 49 | 15 |
1600 | 871 | 58.3 | 47.6 | 60.0 | 32.4 | 28.6 | 47.0 | 59 | 53 | 15 |
1800 | 982 | 32.5 | 28.0 | 15.0 | 17.3 | 15.5 | 8.0 | 71 | 63 | 72 |
2000 | 1093 | 17.3 | 14.8 | 8.3 | 8.2 | 8.0 | 3.9 | 50 | 55 | 99 |
2100 | 1149 | 11.4 | – | 4.5 | 5.6 | – | 2.0 | 40 | – | 99 |
2200 | 1204 | 8.0 | – | 4.4 | 3.7 | – | 1.4 | 31 | – | 99 |