Molybdenum or TZM – which alloy when?
Pure molybdenum or the TZM alloy? Differences in recrystallisation, high-temperature strength, cost and applications compared.
Molybdenum is a refractory metal with a high melting point and good thermal conductivity. TZM is a molybdenum-based alloy that stays significantly stronger and more dimensionally stable at high temperatures. Which material pays off depends mainly on the service temperature and the mechanical load.
Pure molybdenum (Mo)
Molybdenum has a density of around 10.2 g/cm³ and melts at about 2,623 °C. It conducts heat and electricity well and can be used to high temperatures under shielding gas or vacuum. Typical applications: furnace components, heat shields, electrodes and parts in semiconductor and high-temperature technology. Drawback: above approx. 1,100 °C pure molybdenum recrystallises and becomes more brittle.
The TZM alloy
TZM contains small amounts of titanium (~0.5%), zirconium (~0.08%) and carbon in a molybdenum matrix. These additions form fine carbides that stabilise the grain. The result: the recrystallisation temperature rises to around 1,400 °C, and high-temperature strength and creep resistance are well above those of pure molybdenum.
When is TZM worth it?
TZM is worth it wherever components are mechanically loaded above about 1,100 °C – for example hot-working tools, heavily loaded furnace parts, nozzles and forming tools. Where only heat or electrical conduction without high mechanical load is needed, pure molybdenum is usually sufficient and cheaper.
Cost and availability
TZM is more expensive than pure molybdenum because the alloy and its processing are more involved. For many standard applications Mo is the more economical choice; TZM pays off when higher temperature strength decisively improves the part’s service life or safety.
Frequently asked questions
What is the main difference between molybdenum and TZM?
Thanks to fine carbide additions, TZM keeps its strength and dimensional stability at much higher temperatures than pure molybdenum – recrystallisation starts around 1,400 °C instead of ~1,100 °C.
Does TZM have the same melting point as molybdenum?
Approximately yes – TZM is molybdenum-based and melts in a similar range around 2,600 °C. The advantage is not the melting point but the higher strength below it.
When is pure molybdenum enough?
When parts mainly conduct heat or electricity and are not mechanically loaded above the recrystallisation temperature, pure molybdenum is usually sufficient and cheaper.
What is TZM typically used for?
For heavily loaded high-temperature parts such as hot-working tools, nozzles, forming tools and load-bearing furnace components.
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