Properties of molybdenum
The properties of molybdenum and tungsten are very similar, its boiling point and conductivity are outstanding, and its linear thermal expansion coefficient is small, so it is easier to process than tungsten.
The thermal conductivity [135 w / (m · K)] and specific heat [0.276 kJ / (kg · K)] are the best combination, which makes it a natural choice to resist thermal shock and thermal fatigue. Its melting point is 2620 ℃, inferior to that of tungsten and tantalum, but its density is much lower. Therefore, its specific strength (strength / density) is higher than that of tungsten and tantalum. It is more effective in applications with critical weight requirements. Molybdenum still has high strength at 1200 ℃.
The main disadvantages of molybdenum are poor high temperature oxidation resistance (rapid oxidation above 600 ℃) and poor room temperature ductility. In order to make full use of the advantages and avoid the disadvantages, coating (such as MoSi2 coating, nickel plating, chromium plating, etc.) is adopted to control the high-temperature oxidation problem; and the poor plasticity, which is commonly known as the lack of low-temperature embrittlement, is solved by means of alloy strengthening and carbide addition.
Tungsten (W), rhenium (Re), tantalum (Ta), titanium (Ti) and zirconium (Zr) are common solid solution strengthening elements. Tungsten is the main solid solution strengthening element of molybdenum, and rhenium can reduce the ductile brittle transition temperature to - 200 ℃. Industrial molybdenum formed from them. The molybdenum lanthanum alloy composed of lanthanum shows outstanding creep resistance and high temperature deformation ability, especially at high temperature.
