Tungsten-copper alloy for rocket throat lining
Tungsten-based alloy is a kind of metal tungsten based alloy with other metal elements such as copper and molybdenum as auxiliary materials. Because of its excellent physical and chemical properties, it is often widely used in high temperature and other special environments.
Rocket throat lining is made of tungsten-copper alloy because it can withstand high working temperature and mechanical impact.
Solid rocket engine is a chemical rocket engine using solid propellant, which is composed of charge column, combustion chamber, nozzle assembly and ignition device, etc. The rocket engine nozzle is a convergence-diffusion nozzle, which is composed of an inlet section, a throat section and an outlet cone. Its function is to convert the heat energy of combustion products into the kinetic energy of high-speed jet to generate thrust. The expansion ratio, the area ratio between the throat and the nozzle, will directly affect the performance of the engine.
Different from the liquid engine using cooling nozzle, solid engine using ablative nozzle, the inner wall of the nozzle is coated with ablative material, through the ablative evaporation of the material to absorb heat, prevent overheating of the nozzle burning. The lining part of the entire nozzle also needs to undergo greater temperature and pressure.
In fact, whether it is solid or liquid engine, the choice of rocket throat lining material is particularly important. Tungsten-copper alloy is a kind of metal sweat material, so it is the preferred material for modern throat lining.
The alloy is developed based on the principle that tungsten and copper are mutually wetting with each other. It can be prepared by means of powder metallurgy, using tungsten powder as raw material to make a porous structure with certain strength, and the relative density and porosity have strict requirements; Then copper is permeated into porous tungsten skeleton by capillary force to form two-phase composite structure material.
When the engine is working, the copper into the tungsten frame vaporizes and evaporates, absorbing heat, reducing the throat lining temperature and playing a protective role. Due to the effect of copper infiltration, greatly improve the alloy strength, usually 4-5 times higher than the matrix strength legal person, thus improving the thermal shock resistance, improve machinability.
With the development of new materials and new technology, the design and research of throat lining structure have been attached great importance. There are 5 types of throat liner structures that have been applied successively by engines:
1.Heat resistant throat lining structure
Belonging to this category are: plasma sprayed berkelium oxide, pure molybdenum forgings, tungsten-molybdenum alloy castings, tungsten-cobalt cemented carbide integral throat lining structure. It is characterized by heat resistance and thermal deposition by the lining material itself.
2.Heat sink throat lining structure
This category includes: various polycrystalline ink with high sublimation temperature and high thermal conductivity, pyrolytic graphite, felt-based carbon-carbon, multi-dimensional textile carbon-carbon integral throat lining structure. It is also characterized by heat sink resistance to ablation by the lining material itself.
3.Heat resistant and heat sink composite throat lining structure
This category includes: spinning tungsten - graphite, ceramic Mosaic - graphite composite throat lining structure. It is characterized by good heat sink, graphite as throat backing, tungsten, ceramic as throat lining of heat and erosion resistance.
4.Self-cooling and heat sink composite throat lining structure
This category includes: copper tungsten-graphite, tungsten wire reinforced plasma spraying, silver tungsten-graphite composite throat lining structure. It is characterized by spontaneous perspiration cooling material of tungsten copper penetration as heat resistant and anti-scour throat lining and graphite as back lining for heat absorption, so it gives play to the advantages of the two materials, and there is no need to adopt more complex brazing process between the lining and back lining, which has the characteristics of simple process, short period and strong adaptability.
