What are the properties of molybdenum?

Molybdenum belongs to the group of high melting point metals (also known as refractory metals). Refractory metals are metals with a higher melting point than platinum (1772°C). In refractory metals, the binding energy of individual atoms is particularly high. Refractory metals also have high melting points, low vapor pressure, good high-temperature stability, and high elastic modulus in molybdenum-based materials and tungsten-based materials. This type of metal also has typical characteristics such as a low coefficient of thermal expansion and a high density. Molybdenum is in the same group as tungsten in the periodic table, which means the two metals have similar physical and chemical properties. Molybdenum and tungsten also both have excellent thermal conductivity. The difference is that molybdenum deforms easily at considerably lower temperatures, making it easier to machine than tungsten. Molybdenum has a very balanced range of properties, making it a true all-rounder.

Evaporation rate of refractory metals

Vapor pressure of refractory metals

Temperature-dependent linear thermal expansion coefficient of molybdenum and titanium zirconium molybdenum

Temperature-dependent thermal conductivity of molybdenum and titanium zirconium molybdenum

Specific heat of molybdenum and titanium zirconium molybdenum

Resistivity of titanium, zirconium, molybdenum and molybdenum/recrystallized molybdenum lanthanum

Refractory metals generally have smaller thermal expansion coefficients and higher densities. The same goes for molybdenum. The material also has high thermal conductivity and low electrical resistivity. There is strong binding energy between molybdenum atoms, and its elastic modulus is higher than that of many metals. The thermophysical properties of molybdenum change with temperature.

Temperature-dependent linear thermal expansion coefficients of molybdenum and tungsten

Specific heat of molybdenum and tungsten

Temperature-dependent emissivity values ​​for molybdenum

 

 

 

Graph summarizing the temperature-dependent emissivity values ​​of molybdenum (shown as red scattering band). Experimental measurements of the emissivity of Plansee samples under typical delivery conditions can be found at the upper end of the scattering band.

The resistivity ρ (rho) of a material is the reciprocal of its electrical conductivity. The higher the value of a material's resistivity, the worse its electrical conductivity. Resistivity ρ is measured in Ωmm²/m. Different metals have different resistivities. For example: Silver has a resistivity of 0.016 Ωmm²/m and Titanium has a resistivity of 0.427 Ωmm²/m. The temperature, alloying elements, impurities and defects of each material will have a strong impact on the resistivity. Our high-performance materials molybdenum and tungsten have very low resistivities: around 0.05 Ωmm²/m at room temperature; even less than 0.5 Ωmm²/m at 1500°C. Our metals are therefore ideally suited for use as electrical contacts and coating materials. Since molybdenum and tungsten have a cubic lattice, the resistivity is the same in all crystallographic directions. Chart Line chart with 2 lines. View as data table, Chart The chart has 1 X axis displaying Temperature [°C]. Data ranges from 0 to 3369.33. The chart has 1 Y axis displaying Specific electrical resistance [(Ω⋅mm2)/m]. Data ranges from 0.0422192 to 1.16871. End of interactive chart. Resistivity of Molybdenum and Tungsten Enlarge Chart Line chart with 2 lines. View as data table, Chart The chart has 1 X axis displaying Temperature [°C]. Data ranges from 25.4 to 801. The chart has 1 Y axis displaying Thermal conductivity [W/m⋅K)]. Data ranges from 116.8677848 to 174.1113248.

Resistivity of Molybdenum and Tungsten

Temperature-dependent thermal conductivity of molybdenum and tungsten

With a melting point as high as 2620°C, molybdenum maintains its strength and creep resistance even at high temperatures. The higher the degree of shaping of the material, the greater the improvement in molybdenum's strength. Compared with other metals, the ductility of molybdenum materials also increases with the degree of forming. We add rhenium as an alloy element, which can not only improve the ductility of molybdenum, but also reduce the brittle-ductile transition temperature. We also use titanium, zirconium, hafnium, carbon and rare earth oxides as alloying ingredients to add to molybdenum materials. This means that we can create a wide range of materials with a very defined range of properties. Compared with other metals, molybdenum and its alloys have strong binding energy between molybdenum atoms, so they have a very high elastic modulus.

Comparison of the elastic modulus of molybdenum with the elastic modulus of other refractory metals (W, Cr, Ta and Nb) at test temperatures

Typical Yield Strength Values ​​for Molybdenum and Titanium Zirconium Molybdenum 0.2%

Typical tensile strength values ​​for molybdenum and titanium zirconium molybdenum sheets in stress relieved and/or recrystallized conditions (sheet thickness: 2 mm)

Comparison of steady-state creep rates of molybdenum, titanium zirconium molybdenum and recrystallized molybdenum lanthanum sheets at 1100°C

Comparison of steady-state creep rates of molybdenum, titanium zirconium molybdenum and recrystallized molybdenum lanthanum sheets at 1450°C and 1800°C

 

Description of Creep Test Sample Materials：

Typical yield strength values ​​of 0.2% for molybdenum, titanium zirconium molybdenum and molybdenum hafnium carbide rods (diameter: 25 mm; stress relieved condition)

Typical tensile strength values ​​for molybdenum, titanium zirconium molybdenum and molybdenum hafnium carbide rods (diameter: 25 mm; stress-relieved condition)

Temperature hardness values ​​of molybdenum, titanium zirconium molybdenum and molybdenum hafnium carbide rods (diameter: 25 mm; stress-relieved condition)

Optical micrograph of molybdenum sheet (stress relieved)

Optical micrograph of molybdenum sheet (recrystallized)

Optical micrograph of recrystallized molybdenum lanthanum sheet

Brittle-ductile transition temperature:

If heated to a certain temperature, molybdenum loses its brittleness and becomes ductile. The temperature required to transform brittleness into ductility is called the brittle-ductile transition temperature. The brittle-ductile transition temperature is related to many factors, including the chemical composition and degree of deformation of the metal. The ductility of molybdenum decreases with increasing degree of recrystallization. This means that the recrystallization temperature is a decisive factor. The structure changes with recrystallization temperature. This grain remodeling reduces the strength and hardness of molybdenum and increases the likelihood of fracture. Depending on the forming process, operations such as rolling, forging or drawing are required to restore the original structure. The recrystallization temperature depends on the degree of deformation of molybdenum and its chemical composition. Doping with small amounts of oxide particles (such as lanthanum oxide) can increase the recrystallization temperature and creep resistance of molybdenum. The table below summarizes typical recrystallization temperatures for basic molybdenum materials.

In general, during the forming and processing of molybdenum and refractory metals, it is necessary to fully understand the special properties of this group of materials. If chipless forming processes such as bending or folding are used, these processes must be used above the brittle-ductile transition temperature to ensure that the sheet can be processed safely without the risk of cracking. The thicker the sheet, the higher the temperature required for crack-free forming. Molybdenum is also very suitable for cutting and stamping operations if the tool is properly sharpened and the preheat temperature is adjusted correctly. Cutting can also be carried out smoothly with an extremely strong and powerful machine. If you have any questions about processing refractory metals, we'd be happy to use our years of experience to help.

The excellent chemical resistance of molybdenum and its alloys has attracted great attention from the chemical community and glass industry. Molybdenum is corrosion-resistant at atmospheric humidity below 60%. Molybdenum will only start to show fading at higher humidity levels. Molybdenum is no longer corrosion resistant in alkaline and oxidizing liquids at temperatures above 100°C. For applications where molybdenum is used in oxidizing gases and elements above 250°C, we developed the Sibor® protective layer, which protects the molybdenum from oxidation. Glass melts, hydrogen, nitrogen, inert gases, metal melts and oxide ceramics do not corrode molybdenum even at very high temperatures, or corrode molybdenum less than other metallic materials.

The table below lists the corrosion resistance properties of molybdenum. Unless otherwise stated, all specifications are for pure solutions without oxygen. Small concentrations of chemically active impurities can significantly affect the corrosion resistance of molybdenum. If you have any questions about complex corrosion related topics, we are happy to use our experience and in-house corrosion laboratory to assist you.

Corrosion behavior of molybdenum

Molybdenum Flange

Molybdenum Vacuum Plating Evaporation Boat

Pure Molybdenum Flat Head Screws Nuts And Bolts

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