Complete Specification
of
Manufacturing of Iron-Tungsten-Phosphorous-Graphite Hybrid Composite Material through
Powder Metallurgy Route

1 Title of the invention
2 Field of invention
3 Use of invention
4 Prior art
5 Draw backs of prior art
6 Comparison between prior art and present invention
7 Aim of the invention
8 Summary of the present invention
9 .. Brief description of drawings
10 Statement of invention
11 Detailed description of invention
12 Drawings & worked examples

1) Title of the invention
Manufacturing of Iron -Tungsten - Phosphorous - Graphite Hybrid Composite Material through Powder Metallurgy Route.
2) Field of invention
The. present invention is a friction material of Metal-Metal-Lubricant composite having Iron -Tungsten - phosphorous - Graphite formulated through Powder Metallurgy route.
3) Use of invention
The Iron -Tungsten - phosphorous - Graphite composite is used as an aircraft brake pad composition to achieve the desired static co-efficient of friction of 0.20-0.30 & dynamic co-efficient of friction of 0.20-0.23.
4) Prior art
Stator sectors are made through casting technology using cast iron composition. The part produced is having static friction of 0.17 & dynamic fiction 0.20 which is not sufficient for the high kinetic energy absorption condition of the brake unit.
5) Draw backs of prior art
Stator brake sectors produced by casting fail to achieve desired static co-efficient of friction & dynamic co-efficient of friction for the high kinetic energy absorption condition of the brake unit. Manufacturing of the part in casting technology involves high amount of material loss due to shrinkage allowance, pattern allowance and machining allowance.
6) Comparison between prior art and present invention
The dynamic co-efficient of friction is proportional to the dynamic torque developed during the braking application. High Temperature rise during braking application lowers the torque generation of the brake system due to non-presence of lubricant & friction stabilizer in earlier casting brake sector. In the present Iron -Tungsten - phosphorous - Graphite composite, Tungsten acts as friction element with high Toughness which gives required friction at elevated temperature

7) Aim of the invention
Aim of the invention is to develop a new. Metal -Metal - Lubricant composition of Iron -Tungsten - phosphorous - Graphite which gives uniform torque during braking application & desired static & dynamic co-efficient of friction properties.
8) Summary of the present invention
The present invention is formulation of the composite comprising Metal -Metal- Lubricant as Iron -Tungsten - phosphorous - Graphite. The formulated composite finds application in aircraft brake systems. For the said application, the composite needs to have excellent wear properties & fracture toughness of the metallic particles during normal temperature as well as at elevated temperatures during braking applications & also should have stabilized friction co-efficient during elevated temperatures.
These properties are achieved in the present invention by formulating composite with Iron -Tungsten - phosphorous - Graphite powders through powder metallurgy route.
9) Brief description of drawings
Not applicable
10) Statement of invention
Formulation of Iron -Tungsten - phosphorous - Graphite composite through powder metallurgy route for application in the aircraft brake unit as a brake pad (sector). This acts as a friction material in brake pads which needs to stop the aircraft in maximum 10 seconds of time after application of brake. The performance of the brake system shogld be repeatable & precise during normal and elevated temperatures during braking application.

11) Detailed description of invention
The present invention is best suited for braking system of Fighter aircraft with kinetic energy in the range of 6.0-7-2 MJ.
Iron -Tungsten - phosphorous - Graphite composite developed has been proved to be a promising candidate for brake pad applications in the Fighter aircraft.
These brake pads were processed through powder metallurgy technique. The processing sequence involved special mixing technique of preparing metallic and reinforcement mix separately and then blending all mixes together in the ball mill. The composite mix was compacted in a steel cup under uniaxial pressure at room temperature. The green compacts were sintered by pressureless sintering technique under.reducing atmosphere in a pusher furnace.
ANALYSIS AND SOLUTION
Frictional tests on earlier composition of casting stator sector showed that reinforcement and lubricant in the Iron matrix fail to stabilize the friction at higher temperature dissipation (650-700° C) arising from braking energy. The amount and type of reinforcement was insufficient to deliver static & dynamic torque and co-efficient of friction requirement.
To solve this challenge, experiments were carried out on different compositions, namely, Iron-Copper-Silica-Graphite, Iron-Silicon Nitride-Graphite and Iron-Tungsten-Phosphorous-Graphite. These composite pads were tested for braking parameters of Fighter aircraft in full scale brake dynamometer and Static & Dynamic torque testing unit at HAL.
Experimental findings suggested that the Iron -Tungsten - phosphorous - Graphite composite is able to meet the requirement;
Role of Tungsten
A higher volume fraction of Tungsten was found necessary to generate sufficient friction and retain thermal stability at higher dissipation temperatures. The higher volume fraction makes more number of particles to come in contact with counterface and generate higher static & dynamic friction. Further, Tungsten has better fracture toughness than cast Iron and this minimizes the particle fracture assisted wear at elevated temperature.
Role of Phosphorus
The presence of adsorbed vapors such as moisture or volatile organic solvents on graphite is essential to retain its lubricating properties. At higher braking energy, the increased friction temperature deabsorbs all adsorbed vapors and causes the graphite to lose its lubricity. Therefore, the Mechanical Mixed TriboLayer (MMTL) at the interface was not formed by the graphite to stabilize

friction coefficient and wear. To avoid the deabsorbing , phosphorous is added which forms the phosphide which is very hard hence lowers the brake temperature at high energy braking application.
The following table shows the detailed composition of the Iron -Tungsten - phosphorous - Graphite Composite.
Table 2: Iron-Tungsten - phosphorous - Graphite Composite.
SI. no Element Weight Percent
T " Carbon " 4.5-6.5
2. Manganese 0.6-1.0
3. Silicon 1.6-2.3
4. N;ckel 0.8-1.40
6. Chromium 0.8-1.20
7. Tungsten 0.20-0.50
8. Phosphorous 0.30 Max.
9. Iron Remainder
, J ^ ?; \ ■

"We claim"
1 Iron -Tungsten - phosphorous - Graphite Composite is a new frictional composite for aircraft brake application, the details of which is hitherto not available in open literature.
2 The formulation of the composite has been developed by Foundry and Forge Division of HAL, Bangalore and the parameters are optimized for aircraft braking system of 6.0 to 7.2 MJ of Kinetic Energy.
3 The addition of Tungsten & Phosphorus in composition is a new concept to achieve desired friction co-efficient during the spectrum of aircraft energy application at normal & elevated temperatures.
4 The chemical composition of the composite is optimized.
5 The composition is tested in Dynamometer test which simulates aircraft energy as well as on the actual aircraft. The results of these tests were satisfactory& repeatable.
6 The composition is formulated for the aircraft, brake system having Kinetic Energy of