T2 - Thermocouple Alloy Wire - Material Information

T2 thermocouple alloy wire, composed primarily of nickel with controlled additions of aluminum, manganese, and silicon, is widely used as the negative leg of Type K thermocouples. This alloy is specifically engineered for high stability, oxidation resistance, and reliable performance at elevated temperatures up to 1250 °C in oxidizing atmospheres. Its combination of mechanical integrity and thermoelectric consistency makes it one of the most dependable materials for industrial and research temperature sensing.

Material Overview

The Ni–Al–Mn–Si alloy system offers a balanced combination of thermal stability and oxidation resistance. Additions of Si (0.5–3 %) enhance the formation of protective Ni–Si–O surface oxides, improving resistance to scale spallation and extending service life (Tyuvin et al., 1977). Aluminum contributes to the formation of Al2O3 within the oxide scale, while manganese stabilizes the solid solution and enhances hot strength. The alloy maintains a stable electromotive force (EMF) relationship with chromel (the Type K positive leg) under long-term exposure, with minimal drift even after 1000 h at 1100 °C. Microstructural stability is further supported by Ni–Mn and Ni–Al solid solutions that resist grain coarsening and interdiffusion. When tested under oxidizing conditions, Ni–Al–Mn–Si alloys maintain steady oxidation rates up to 1200 °C, comparable to high-grade superalloys such as Nimonic 95 (Li et al., 2021).

Applications and Advantages

T2 thermocouple wires are extensively employed in temperature control systems for furnaces, gas turbines, and heat-treatment processes. They deliver consistent EMF output across extended temperature cycles and resist degradation in oxygen-rich environments. Wang et al. (2016) demonstrated that optimized Ni–Co–Mn or Ni–Al–Mn thermocouple alloys can remain stable in strong oxidizing atmospheres for over 1000 h at 1150 °C. Compared with older Ni–Mg or Ni–Cr thermoelements, T2 offers lower EMF drift and improved calibration retention, reducing the need for frequent recalibration in precision instrumentation. Its mechanical strength and oxidation resistance also allow for long operational life under both static and dynamic thermal loading conditions.

Goodfellow Availability

Goodfellow supplies T2 thermocouple alloy wire in high-purity research and industrial formats. These materials combine high-temperature oxidation resistance with consistent thermoelectric performance for accurate and durable temperature measurement. Explore thermocouple alloys and related high-performance materials through the Goodfellow product finder.

References

• Li, D., Chen, J., Etim, I. P., Liu, Y., Wu, C., Wang, J., & Su, X. (2021). High-temperature oxidation behavior of Ni-based superalloy Nimonic 95 and the effect of pre-oxidation treatment. Vacuum, 190, 110582. https://doi.org/10.1016/j.vacuum.2021.110582
• Tyuvin, Yu. D., Rogel’berg, I. L., Ryabkina, M. M., & Plakushchaya, A. F. (1977). Oxidation resistance of nickel alloys. Metal Science and Heat Treatment, 19(11), 838–842. https://doi.org/10.1007/BF00670157
• Wang, H., Zhang, S., Zou, X., Liu, Y., Li, F., Zhang, D., Yang, B., Guo, W., & Ju, B. (2016). Thermocouple material achieving stable temperature measurement in oxidizing medium and preparation method of thermocouple material. Chinese Patent CN105401231A.
• Starr, C., & Wang, T. (1973). Thermocouple with nickel–silicon–magnesium alloy negative element. U.S. Patent 3,726,743.
• Smialek, J. L., & Gedwill, M. G. (1993). High temperature, oxidation resistant noble metal–Al alloy thermocouple. U.S. Patent 5,224,838.