REFRACTORIES IN AEROSPACE INDUSTRY

GROUP NO.7 BATCH: 2012 2013

M. Haris Bin Riaz MY-56

Ahsan Zaman MY-16

Syed Ahsan Iqbal MY-45

Abdul Rehman Siddiqui MY-50

Saad Bin Shaheen MY-67

Subject Teacher: Engr. Rizwan

DEPARTMENT OF METALLURGICAL ENGINEERING

NED UNIVERSITY OF ENGINEERING & TECHNOLOGY

Refractory materials are those, which stubbornly resists high and low temperaRefractories have high melting point them applicable for structures or as components of systems that are exposed to environment about 1000oF(538oC). It has the ability to withstand load, thermal shockhot gases etc. it further has high compressive strength, high toughness and low thermal conductivity. This unique property of refractory makes them suitable and applicable for different industries of the world.

AEROSPACE APPLICATThe bright future has been predicted for the refractory for aerospace applications. The typical uses include:-1. Rocket motor nozzles2. Space shuttle tiles 3. Aircraft engines 4. Missile nose-cones 5. Unmanned air vehicles

1. ROCKET MOTOR NOZZLESA rocket engine nozzle is a device which is combustion gases produced by burning propellantsat hypersonic velocities. (Hypersonic velocity means sound.)

Consider a space shuttle with its nozzle at the bottom as shown in Fig.1.up of a material which have low melting point and low toughnesslaunched?

INTRODUCTIONRefractory materials are those, which stubbornly resists high and low tempera

have high melting point having those chemical and physical properties that make them applicable for structures or as components of systems that are exposed to environment

It has the ability to withstand load, thermal shock, action of molten metals, hot gases etc. it further has high compressive strength, high toughness and low thermal conductivity. This unique property of refractory makes them suitable and applicable for different

AEROSPACE APPLICATIONSThe bright future has been predicted for the refractory for aerospace applications. The typical

ROCKET MOTOR NOZZLESdevice which is used in a rocket engine to expand and accelerate the

combustion gases produced by burning propellants (fuel) so that the exhaust gases exit the nozzle Hypersonic velocity means with a velocity greater than the velocity of

Fig.1 Space shuttle nozzle

with its nozzle at the bottom as shown in Fig.1. Let the nozzlematerial which have low melting point and low toughness. What will happen if it is

Fig.1 Space Shuttle Nozzles

Refractory materials are those, which stubbornly resists high and low temperature zones. having those chemical and physical properties that make

them applicable for structures or as components of systems that are exposed to environment , action of molten metals,

hot gases etc. it further has high compressive strength, high toughness and low thermal conductivity. This unique property of refractory makes them suitable and applicable for different

The bright future has been predicted for the refractory for aerospace applications. The typical

used in a rocket engine to expand and accelerate the so that the exhaust gases exit the nozzle

with a velocity greater than the velocity of

Let the nozzle is made hat will happen if it is

Just after the launch, the highly generated exhaust gas which has a temperature of approximately 3200oC will immediately melt the nozzle and the space shuttle won’t go upward.

So to overcome this hazard, we need a special material with high Melting point; low thermal conductivity, high strength and high Thermal shock resistance because there is a sudden increase in temperature.

All we know is a refractory which has all these characteristics. The material which is used in nozzle manufacturing includes refractory metals such as Molybdenum and Tungsten; the second would be carbide of refractory metals such as zirconium carbides, tantalum carbide etc.

2. SPACE SHUTTLE TILESSpace shuttle tiles look similar to normal tiles but they are not the ordinary tiles. These tiles are specially made for space shuttles and major external parts of space shuttle are coated by these tiles. These tiles can be divided into three main parts. As shown in fig.2

i. Lower level tilesii. Upper level tiles

iii. Leading edge tiles

i. Leading Edge TilesThe leading edges of the Orbiter’s wings are coated with reinforced carbon-carbon. This provides extra protection to the areas which are hottest during re-entry.Temperatures on these surfaces can exceed to 3,000oF.

Reinforced Carbon-Carbon is a lightweight heat-shielding material used on the wing leading edge and nose cap of the shuttle.

RCC is then impregnated with furfural alcohol in a vacuum chamber, then cured and pyrolized again to convert the furfural alcohol to carbon. This process is repeated three times until the

Fig.2 Types of space shuttle tiles

desired carbon-carbon properties are achieved. That’s way leading edge tiles are called Reinforced Carbon-Carbon.

ii. High-temperature reusable surface insulation

HRSI tiles black in color provides protection against temperatures up to 1,260 °C (2,300 °F).

The HRSI tiles are made of a low-density, high-purity silica 99.8-percent amorphous insulation that is made rigid by ceramic bonding. Because 90 percent of the tile is void and the remaining 10 percent is material, the tile weighs approximately 9 pounds per cubic foot.

iii. Fibrous refractory composite insulation (FRCI) tiles

FRCI tiles are derived by adding (alumina-borosilicate fiber), called Nextel, to the pure silica tile slurry. It’s used to provide improved strength, durability, resistance to coating cracking and weight reduction. Some HRSI tiles were replaced by this type.

After Lower Level Tiles now comes Upper Level Tiles. these tiles are known as Low-temperature reusable surface insulation (LRSI).

iv. Low-temperature reusable surface insulation (LRSI)

White in color, these covered the upper wing near the leading edge. They were also used in selected areas of the forward, mid, and aft fuselage, vertical tail, and the OMS/RCS pods. These tiles protected areas where reentry temperatures are below 1,200 °F (649 °C).

The LRSI tiles are of the same construction and have the same basic functions as the 99.8-percent-pure silica HRSI tiles, but they are thinner (0.2 to 1.4 inches) than HRSI tiles. Thickness is determined by the heat load encountered during entry. The 99.8-percent-pure silica LRSI tiles are manufactured in the same manner as the 99.8-percent-pure silica HRSI tiles, except that the tiles are 8- by 8-inch squares and have a white optical and moisture-resistant coating applied 10 mils thick to the top and sides. The white coating provides on-orbit thermal control for the orbiter. That is why these tiles are the best tiles because of their low thermal conductivity. The coating is made of silica compounds with shiny aluminum oxide to obtain optical properties.

3. AIRCRAFT ENGINESince the invention of the jet engine and its use in the aerospace industry, the aim has always been to increase turbine operating temperatures since this means better efficiency, more power, less fuel consumption and less pollution for airplanes. In fact, during the past 30 years turbine airfoil temperature capability has increased on average by about 4°F per year. Similarly, in modern jet engines can reach temperatures as high as about 1,150° C. This created a big challenge since the operating temperatures of turbines were limited by how much their material could handle.

Refractory metals (Ni-based super alloys) with their high melting point are being increasingly considered as alloying elements and even as base elements as a heat resisting barrier in engines as shown in fig.3

Refractory elements and their alloys are proving to have better properties not only do they exhibit higher melting points but they also have better thermal and mechanical properties of oxidation, creep and corrosion at high temperature from 1500°C to 1800°C. Researchers investigate the foaming possibilities and processes of the ultra-high temperature alloys. This porous structure will be known as Refractory Open Cell Metal Foam.

4. MISSILE NOSE-CONESDue to the extreme temperatures involved, nose cones for high-speed applications (e.g. hypersonic speeds) have to be made of refractory materials because they have excellent strength at high temperatures. Refractory metals, such as tungsten, molybdenum and tantalum can be used in missile noses as shown in fig.4 because it has the highest melting point of all the refractory metals.

Fig.3 Engine of an aircraft

Fig.4 The nose of tungsten alloy at the top

In addition, tungsten has excellent resistance to the chemical corrosion of the hot gases. Furthermore, it resists abrasive erosion and has excellent high temperature strength even when heated to 1000oC tungsten rocket nose cones still have twice the tensile strength iron has at room temperature. Because of these properties molybdenum is also useful in many high temperature applications where high melting points are required. Molybdenum also exhibits good strength at elevated temperatures making it useful in aerospace and similar applications.

5. UNMANNED AIR VEHICLE An unmanned aerial vehicle (UAV), commonly known as drone is an aircraft without a human pilot aboard as shown in fig.5. Its flight is controlled either autonomously by onboard computers or by the remote control of a pilot on the ground or in another vehicle

Refractory is used in UAV such as Niobium C-103 is used because of five main reasons

It has low density (due to which it can easily fly).

High stress levels at elevated temperatures.

Low cost.

It has low ductile-to-brittle transition temperature for withstanding high frequency vibrations at cryogenic temperatures.

Niobium C-103 is used with a protective coating of Molybdenum/Tungsten and Silicon/Germanium to protect its layer from high temperature corrosion.

CONCLUSION:

The summary of this report is that in this era if scientists have made tremendous progress in aerospace sector this is only due to refractory. If refractory does not invent, may be aerospace sector does not exist in this world.

Fig.5 Unmanned air vehicle (UAV) or drone