| Sheath Material |
Approximate Melting Point |
Maximum recommended
temperature |
Environment |
Remarks |
| Platinum -
10% Rhodium (Pt - 10% Rh) |
3360°F (1850°C) |
2825°F (1550°C) |
Oxidizing, inert, vacuum |
Used primarily in oxidizing environments to
2825°F (1550°C). Applications include semiconductor manufacturing, research
and gas turbine probes. Silicon, sulphur and carbon are contaminants of
platinum and should be avoided. |
| Platinum -
20% Rhodium (Pt - 20% Rh) |
3400°F (1870°C) |
3000°F (1650°C) |
Oxidizing, inert, vacuum |
Same uses as platinum - 10% rhodium; except
usable to 3000°F (1650°C) with increased high temperature strength. |
| Molybdenum (Mo) |
4750°F (2620°C) |
3450°F (1900°C) |
Inert, vacuum, reducing |
Molybdenum is a refractory metal that is
brittle and available in un-compacted styles only. Do not use in oxidizing
environments above 750°C (400°C). Vacuum at <10(-2) torr to 3100°F (1700°C).
Vacuum <10(-4) torr to 3400°F (1870°C). Stable in inert gases to 3450°F
(1900°C). Avoid contamination with graphite, carbon and hydrocarbons. |
| Tantalum (Ta) |
5425°F (2995°C) |
4350°F (2400°C) |
Inert, vacuum |
Refractory metal that is very ductile. Use
only in inert atmospheres or very good vacuums. <10(-3) torr. Hydrogen and
nitrogen will react with tantalum above 750°F (400°C) resulting in nitride
and hydride formation that will affect life. Tantalum is one of the best
corrosion resistant metals available for the chemical industry. |
| Titanium (Ti) |
3135°F (1725°C) |
Oxidizing 600°F (315°C) |
Oxidizing to 600°F (315°C), Inert, vacuum |
Lightweight, excellent strength in the 300 to
800°F (150 to 425°C) temperature range. Excellent resistance to oxidizing
agents such as nitric or chromic acids. Resistance to inorganic chloride
solutions, chlorinated organic compounds and moist chlorine gas. Resistant
to salt water spray and salt water. |
| Niobium (Nb) 1% Zirconium |
4525°F (2495°C) |
2400°F (1315°C) |
Inert, vacuum |
Good resistance to sulphuric, nitric and
hydrochloric acids within defined limits. Also used in liquid metals such as
lithium, sodium potassium, lead, mercury and bismuth providing oxygen is
less than 40 ppm. |
| Tungsten (W) |
6170°F (3410°C) |
4500°F (2480°C) |
Inert, vacuum, reducing |
Tungsten has the highest melting point of any
metal. Available only in loose pack constructions due to it's brittle
nature. Good wet and abrasion resistance. Lowest vapour pressure of all
metals. Can be used in hydrogen at all temperatures. |
| Alloy 600 |
2470°F (1345°C) |
2150°F (1175°C) |
Inert, vacuum, reducing, oxidizing |
Maximum temperature 2150°F (1175°C). Most
widely used thermocouple sheath material. Good high temperature strength,
corrosion resistance, resistance to chloride-ion stress corrosion cracking
and oxidation resistance to high temperatures. Do not use in sulphur bearing
environments. Good in nitriding environments. |
