Tungsten has the highest melting point of all metals, a low thermal coefficient of expansion, and a high density.
The good electrical conductivity and the excellent thermal conductivity of tungsten should also be mentioned. All of these properties are more pronounced in tungsten than in molybdenum.
The physical properties of tungsten change with temperature. The diagrams below illustrate the curves for the most important scales for a comparison:
The graph (top right) summarizes the temperature-dependent values of emissivity of tungsten (shown as blue scatter band) available in the literature. Experimentally measured values of emissivity of Plansee samples in typical as-delivered condition can be found on the upper end of the scatter band.
Tungsten has similar mechanical properties to molybdenum. Like with molybdenum, these properties are dependent on the testing temperature. At 3420 °C,
tungsten has the highest melting point of all metals,
a high modulus of elasticity, and a high heat and creep resistance.
At Plansee, we optimize the material purity, determine the type and quantity of alloying components, and modify the microstructure of the material through targeted thermomechanical treatment, a combination of deforming and heat treatment. This results in customized mechanical properties for the most diverse applications.
Like molybdenum, tungsten has a body-centered cubic lattice and therefore the same characteristic brittle-to-ductile transition. The brittle-to-ductile transition temperature can be reduced by means of forming and alloying. The strength of the material increases with an increasing degree of deformation. However, unlike other metals, this also increases the ductility of tungsten. The main alloy element used to improve the overall ductility of tungsten is rhenium.
The term "doping" comes from the Latin "dotare" and means "provide with". In the world of metallurgy, doping refers to the introduction of one or more alloying elements in the microgram range. The term "microalloying" is also often used. The alloy content introduced during doping may reach several hundred micrograms [mg]/g. The amount of doping quantity is frequently given in ppm (ppm by weight). The abbreviation ppm stands for "parts per million", i.e., 10-6.
If you are intending to use tungsten at high temperatures, you should take account of the material's recrystallization temperature. When it comes to tungsten materials, the ductility, in particular, along with the strength of the material decreases with a rising recrystallization level. Doping with small oxide particles or bubbles (e.g., lanthanum oxide or cerium oxide) increases the recrystallization temperature and creep resistance of tungsten. The higher the deformation, the stronger the effect when it comes to the oxide, which becomes finer due to the thermomechanical processing.
The table indicates the recrystallization temperatures of our tungsten-based materials at different levels of deformation:
| Material | Temperature [°C] for 100% recrystallization (annealing time: 1 hour) | |
| Level of deformation = 90% | Level of deformation = 99.99% | |
| W (pure) | 1350 | - |
| WVM | - | 2000 |
| WL10 | 1500 | 2500 |
| WL15 | 1550 | 2600 |
| WRe05 | 1700 | - |
| WRe26 | 1750 | - |
| WC20 | 1550 | 2600 |
The machining of tungsten requires a real feeling for the material. Chipless forming processes such as bending or folding must generally be applied at above the brittle-to-ductile transition temperature. In the case of tungsten, this temperature is higher than for molybdenum. The thicker the sheets that are to be processed, the higher the required preheating temperature. The sheets need a higher preheating temperature for cutting and punching than for folding operations. It is very difficult to use machining processes with tungsten. Our tungsten alloys using lanthanum oxide are somewhat easier to machine. However, the level of tool wear is still very considerable and chipping may also occur in tungsten.
If you have any specific questions relating to the machining of refractory metals, we would be glad to assist you with our many years of experience.
Tungsten is corrosion-resistant at a relative humidity of under 60%. In moister air, discoloration starts to occur; however, this is less pronounced than for molybdenum. Even at very high temperatures, glass melts, hydrogen, nitrogen, noble gases, metal melts, and oxide ceramic melts are largely unaggressive to tungsten provided that they do not also contain oxidants.
The table below indicates the corrosion behavior of tungsten. Unless otherwise indicated, the specifications relate to pure solutions not mixed with air or nitrogen. Tiny concentrations of extraneous chemically active substances can significantly affect the corrosion behavior. Do you have any questions regarding complex corrosion-related topics? We would be delighted to help you with our experience and our in-house corrosion laboratory.
Tungsten is corrosion-resistant at a relative humidity of under 60%. In moister air, discoloration starts to occur. However, this is less pronounced than in molybdenum. Even at very high temperatures, glass melts, hydrogen, nitrogen, noble gases, metal melts, and oxide ceramic melts are largely unaggressive to tungsten provided that they do not also contain oxidants.
The table below indicates the corrosion behavior of tungsten. Unless otherwise indicated, the specifications relate to pure solutions not mixed with air or nitrogen. Tiny concentrations of extraneous chemically active substances can significantly affect the corrosion behavior. Do you have any questions regarding complex corrosion-related topics? We would be delighted to help you with our experience and our in-house corrosion laboratory.
| MEDIUM | RESISTANT (+), NON-RESISTANT (-) | NOTE |
| Water | ||
| Cold and warm water < 80 °C | + | |
| Hot water > 80 °C, deaerated | + | |
| Acids | ||
| Hydrofluoric acid, HF | + |
< 100 °C |
| Hydrochloric acid, HCI | + | |
| Phosphoric acid, H3PO4 | + | < 250 °C |
| Sulfuric acid, H2SO4 | + | < 70%, < 190 °C |
| Nitric acid, HNO3 | + | |
| Nitro hydrochloric acid, HNO3 + 3 HCl | + | < 30 °C |
| Organic acids | + | |
| Lyes | ||
| Ammonia solution, NH4OH | + | |
| Potassium hydroxide, KOH | + | < 50%, < 100 °C |
| Sodium hydroxide, NaOH | + | < 50%, < 100 °C |
| Halogens | ||
| Fluorine, F2 | - | |
| Chlorine, Cl2 | + | < 250 °C |
| Bromine, Br2 | + | < 450 °C |
| Iodine, I2 | + | < 450 °C |
| Non-metals | ||
| Borine, B | + | < 1200 °C |
| Carbon, C | + | < 1200 °C |
| Silicon, Si | + | < 900 °C |
| Phosphorous, P | + | < 800 °C |
| Sulfur, S | + | < 500 °C |
| Gases* | ||
| Ammonia, NH3 | + | < 950 °C |
| Carbon monoxide, CO | + | < 1400 °C |
| Carbon dioxide, CO2 | + | < 1200 °C |
| Hydrocarbons | + | < 1200 °C |
| Air and oxygen, O2 | + | < 500 °C |
| Inert gases (He, Ar, N2) | + | |
| Hydrogen, H2 | + | |
| *Special attention must be paid to the dew point of the gases. Moisture can lead to oxidation. | ||
| Melts | ||
| Glass melts* | + | < 1700 °C |
| Aluminum, Al | + |
< 700 °C |
| Beryllium, Be | - | |
| Bismuth, Bi | + | < 1400 °C |
| Cer, Ce | + | < 800 °C |
| Copper, Cu | + | < 1300 °C |
| Gallium, Ga | + | < 1000 °C |
| Gold, Au | + | < 1100 °C |
| Iron, Fe | - | |
| Lead, Pb | + | < 1100 °C |
| Lithium, Li | + | < 1600 °C |
| Magnesium, Mg | + | < 700°C |
| Mercury, Hg | + | < 600 °C |
| Nickel, Ni | - | |
| Plutonium, Pu | + | < 700 °C |
| Potassium, K | + | < 1200 °C |
| Rubidium, Rb | + | < 1200 °C |
| Samarium, Sm | + | < 800 °C |
| Scandium, Sc | + | < 1400 °C |
| Silver, Ag | + | |
| Sodium, Na | + | < 600 °C |
| Tin, Sn | + | < 980 °C |
| Uranium, U | + | < 900 °C |
| Zinc, Zn | + | < 700 °C |
| Furnace construction materials | ||
| Alumina, Al2O3 | + | < 1900 °C |
| Beryllium oxide, BeO | + | < 2000 °C |
| Graphite, C | + | < 1200 °C |
| Magnesium oxide, MgO | + | < 1600 °C |
| Silicon carbide, SiC | + | < 1300 °C |
| Zirconium oxide, ZrO2 | + | < 1900 °C |
Corrosion behavior of tungsten against selected substances
If you have any questions or are looking for a suitable material composition for your application, get in touch with us!
Would you like to learn more about tungsten and its alloys? Then please see our material brochure and product data sheets here.
