Molybdenum Alloys for Rocket Engines

Rocket engines, also known as rocket boosters, are mainly made of lighter high-temperature alloys such as molybdenum alloys, which can not only effectively reduce the weight of aviation equipment, but also extend the service time of the booster.

The rocket booster is a jet engine that uses the principle of impulse, has its own propellant, and does not rely on outside air. The propellant is composed of oxidizer and fuel, and it is burned at high pressure (10-200bar) in the combustion chamber to produce gas. Due to the high working temperature, the high temperature resistance of its constituent materials should be better, and the coefficient of thermal expansion should be low, otherwise it is prone to volume deformation or even melting.

Compared with other alloy materials, molybdenum-based alloys are more suitable for use in jet engines. Although it does not have the high temperature resistance of tungsten alloys, its specific gravity is less than that of tungsten alloys, and its high temperature resistance is far superior to the existing nickel-based and cobalt-based alloys.

According to the number of added elements, molybdenum-based alloys can be divided into binary alloys and multi-element alloys. Binary alloys refer to molybdenum alloys in which a single alloying element is added to molybdenum. They can be divided into two categories: one is alloys with tungsten and rhenium as alloying elements, which have the characteristics of high hardness and high heat resistance; the other is The alloy with titanium and hafnium as alloying elements has less addition and the alloy performance is slightly higher than pure molybdenum.

Multi-element alloys are based on binary molybdenum alloys. In order to further improve the properties of the alloy, a second or more alloy components are added to form an alloy with certain excellent properties. There are mainly the following series: Mo-Ti-Zr-C series, Mo-Hf-Zr-0 series, Mo-W-Hf-C series. Due to different doping elements, their physical and chemical properties and functions are also different. For example, Mo-W-Hf-C series alloys have the characteristics of high strength, high hardness, and good high temperature resistance.

In rocket engines, multi-element molybdenum alloys are commonly used as high temperature resistant materials.