FIELD OF INVENTION
This invention relates to a process for manufacturing cermet friction materials/composites/brake elements with builtin backing plates using hot powder forging with built in backing plate for medium to heavy-duty applications.
PRIOR ART
In order to meet diverse and severe conditions in brake application such as very high energy dissipation without fading of the friction material, Cermet brakes contain large number of metallic and non-metallic constituents where non-metallic content is as high as 30 wt% and thus manufacturing of these brake materials is possible only through powder metallurgical route, comprising of compacting and sintering till now. The references may be made to the following:
US Patent 6143051 :- describing a method of preparing a friction material, where in a mixture of iron fibers, iron particles, graphite particles and metallic binder is cold pressed at a pressure of at least 100 MPa to form compacts which are sintered at 800-1140"C for a long time. It does not however, include ceramics components which are needed for heavy duty brake elements.

US Patent 6110268:- describing a method for manufacturing a fiber reinforced ceramic brake member/brake lining wherein a mixture of carbon particles, metal particles with polymer binding agent, silicon carbide or titanium carbide particles as abradants and solid lubricants are cold pressed into green compacts and then sintered in vacuum or protective aLmosphere.
US Patent 5925837:- describing a method for manufacture of copper based metallic friction material comprising of powder preparation, pressing to form green compacts under 375-625 MPa at room temperature, preheating at 100-300°C for 1-3 hours, sintering the green bodies under 350-750 MPa for 24-60 hours and then grinding, polishing and washing.
US Patent 5324592:- describing a forming technique for manufacturing a copper powder free friction material which is made by sintering containing powdery and/or granular metallic and non-metallic components.

US Patent 4576872;- describing a method of manufacturing a friction clement which beds-in quickly and which has a 'feel' similar to a resin based element where the powdered metallic friction material is subjected to resistance sintering, so as to produce a sintered substrate and un-sintered or partly sintered surface layer.
US Patent 3341931:- describing a method of producing railroad brake shoe, in the form of a sintered body of powdered metal including iron and graphite, by subjecting the sintered body to repeated pressure at elevated temperature.
US Patents as cited above do not cover the joining of friction material with that of baking plate and the perfectness of joint or the joint strength. Further, all these patents comprising steps of compacting and sintering in manufacturing a brake element.
IP 198715/2002 deals with the preparation of metal-ceramic (Fe-based and Cu-based) friction materials with cup type or flat plate type steel baking frames by compacting .MH! smtermg wherein the baking plate is joined by pressure sintering.

US Patent 4278153 describing friction modules with the grid reinforcement in either a mold or within the brake disc cup using sintering in the manufacture of brake.
Further, reference may be made to the available literature on 'Process of manufacturing cermet friction elements', which is listed below:
1. Chan, 13., Stachowiak 'Review of automotive brake friction
materials' Proc. Instn Mech. Engineers, 2004, Vol. 218 Part D,
Automobile Engineering, pp 953-966 (D 13103).
2. Krishnadas, C. G., Dutta, D Mohan, G. 'Development of
Metalloceramic Friction Materials for aircraft brake' (ISBN 0-
87339-251-5), International Conference on Advanced
Composites: Advanced Composites' '93 held on Feb. 15-19,
1993 at Wollongong (Australia).
3. Prasad, R.C., Ramakrishan, P., 'Composites: Science and
Technology (ISBN 81-224-1251-3), New Age International (P)
Ltd., New Delhi, Page 94-1 14.

4. Hausner, Henery H. Roll, Kempton H., and Johnson, Peter K.
'Friction and Antifriction Materials' Volume 4, 1970, Plenum
Press, N ew Y o r k - Lo n d o n.
5. Newman, Louis B., 'Friction Materials Recent Advances' 1978,
Noyes Data Corporation, Park Ridge, NJ, USA.
The process of manufacturing cermet brake elements comprising steps of compacting and sintering, ass. •. iaiod with the following drawbacks:
(i) Considerable capital investment in the form of costly
equipments, (ii) Substantial rejection rate in compacting and sintering
due to brittle nature of the product, (iii) Poor density of the resulting product due to cold
compacting and limited pressure application at high
temperature pressure -sintering, (iv) Inadequate joining of backing plate with friction element
due to improper wetting characteristics at the interface.

(v) Expensive manufacturing technique due to involvement of
a number of complex operations. (vij Costly raw materials owing to precise requirement of cold
compacting process and (vii) The resulting product also suffers from wide variations in
final characirn<:iirs due to requirement of large number
of complex operations in the compacting and sintering.
OBJECTS OF THE INVENTION
An object of this invention is to propose a process for manufacture of metal for example iron/copper based cermet friction elements/composites in desired shapes and sizes using hot powder forging with built in backing plate, which are suitable for medium to heavy duty applications in aiuoniouiles, rails and aircrafts.
Another object of this invention is to propose a process for manufacturing cermet friction materials/composites/brake elements with builtin backing plates using hot powder forging with built in backing plate for medium to heavy-duty applications which overcomes the limitations and drawbacks

of prior art by eliminating the compacting arid sintering and joining the backing plates with friction material during forging process.
Further object of this invention is to propose a process for manufacturing cermet friction materials/composites/brake elements with builtin backing plates using hot powder forging with built in backing plate for medium to heavy-duty applies !ions, which gives desired shape, contour and size of the friction element and baking plate in one operation only namely forging.
Yet another object of this invention is to propose a process for manufacturing cermet friction materials/composites/brake elements writh built in backing plates using hot powder forging with built in backing plate for medium to heavy-duty applications, which ensures a good interfacial metallurgical bonding between friction material and supporting backing member and withstands the severe torque and temperature rise in braking for medium to heavy duty automobiles, rails and aircrafts etc.

Still another object of this invention is to propose a process for manufacturing cermet friction materials/composites/brake elements with builtin backing plates using hot powder forging with built in backing plate for medium to heavy-duty applications, which results in the improvement of the quality of product as produced by compacting and sintering.
Still another further object of this invention is to propose a process for manufacturing cermet friction materials/composites/brake elements with builtin backing plates using hot powder forging with built in backing plate for medium to heavy-duty applications, to develop new friction materials/brake elements with simpler chemistry, desired density, low wear loss, stable coefficient of friction and long life suitable for brake employed in heavy-duty applications.
Yet further object of this invention is to propose a process for manufacturing cermet friction materials/composites/brake elements with builtin backing plates using hot powder forging with built in

backing plate for medium to heavy-duty applications, to reduce failure rate due to breakage and warpage of the product during manufacture.
Still another object of this invention is to propose a process for manufacturing cermet friction materials/composites/brake elements with builtin backing plates using hot powder forging with built in backing plate for medium to heavy-duty applications, to avoid use of sophisticated custom built equipments.
Still further object of this invention is to propose a process for manufacturing cermet friction materials/composites/brake elements with builtin backing plates using hot powder forging with built in backing plate for medium to heavy-duty applications, to develop a cost effective technique for manuf;-,,••.. nrr of metallo-ceramic friction elements.
Further object of this invention is to propose a process for manufacturing cermet friction materials/composites/brake elements with builtin backing plates using hot powder forging with built in backing plate for medium to heavy-duty applications, which overcomes disadvantages of the prior art and in which the brake elements are more durable.
STATEMENT OF INVENTION
According to this invention there is provided a process for manufacturing cermet friction materials/composites/brake elements with builtin backing plates comprising steps of preparation of a mixture comprising a mix of metals and non-metals as herein described and ceramics added with lubricants such as herein described, mixing for 2- 4 hours, encapsulation of the mixture thus obtained in a capsule, supplied with dry Hydrogen through one of its end, other end of which is ignited to ensure dry Hydrogen atmosphere inside, the said capsule is heated at 1000-1100° for 0.5-2 hrs for iron based friction elements and at 750-900°C for 0.52 hrs for copper based friction elements, hot forging carried out with 1-5 hammer blows in hot condition in which the ram speed and impact load is 150-350 mm/sec and 120- ns respectively for a forged slab area of 60-80 cm2, followed by homogenization at 1000-1200°C for 0.5-2 hrs for iron based friction elements and at 750-950°C for 0.5-2hrs in case of copper based friction elements followed by repressing performed in a hydraulic press for 0-4 times, annealing 680-950°C for 2-5 hrs for iron base friction elements and at 600-850°C for 0.5-2 hrs in case of copper based friction elements to adjust hardness of the elements.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Further objects and advantages of this invention will be more apparent from the ensuing description when read in conjunction with the accompanying drawings and wherein:
Fig. 1 shows: a flow chart for the process of present invention.
Fig. 2 shows: Top view (plan) of a steel capsule used in the invention.
DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE ACCOMPANYING DRAWINGS
Reference may be made lo fig. 1 indicating steps involved in the process
for the manufacture of cermet friction materials etc.
The chemistry of friction materials as per table suggested below or any other chemistry related to compacting and sintering process can be utilized for making friction elements.
Table 1 :- suggested chemistry for friction materials which may be taken as an example without restricting scope of the invention to the same.

(Table Remove)
The powder of metal such as Fe/Cu, powder of ferro-alloy, which is optional and other metal powders in a range of 150-250 micron are blended for 2-6 hrs in dry medium as per table given above.
Thereafter, ceramic and non-metals are mixed in wet medium with ethanol which is for example 50% by volume followed by blending for 0.5-2 hrs and drying at 80-120°C for about 1-2 hrs wherein the ceramic and nonmetals such as carbides are taken as per table given below so as to meet the desired chemistry of the friction element.
The powder mixtures obtained above are mixed for about 2-4 hrs followed by addition of solid lubricants such as graphite, MoS2 and further mixing of the powder mix for 2-4 hrs.
The powder mixture thus prepared is encapsulated in a capsule as shown in fig. 2 made of for example: mild steel, inside of which is coated with copper having thickness of 50-150 milirnicron in case of iron based friction elements wherein iron is predominant. In case of copper based friction element wherein copper is predominant, inside of the steel

capsule is left uncoated. The size of steel capsule depends on the actual size of brake element and number of the elements to be produced. The steel capsule serves essentially two purposes. Firstly to protect powders from high temperature o-^cb.tion during pre-heating, forging, homogenization, hot-repressing and annealing. Secondly, to serve as backing plate of the final product.
The constituents for Fe-based/Cu-based friction materials among the metallic, non-metallic, ceramics and solid lubricants (like Fe, Cu, Al, Sn, Ferro alloys, graphite, SiC, WC, MoS^, Sb^S2 etc) are selected according to the requirement.
The capsule encapsulated with the powder mix is treated with dry Hydrogen. The Hydrogen is supplied through one end of the capsule, other end of which is ignited to ensure dry Hydrogen atmosphere inside the capsule. The capsule is heated at 150-1]00°C for 0.5-2 hrs for iron-based friction elements and at 750-900"C for 0.5-2 hrs in case of copper based friction elements. This is followed by hot forging with 1-5 hammer blows in hot condition. The ram speed and impact load in forging lies

between 150-350 mm/sec and 120-250 tons respectively for a forged slab area of 60-80 cm-'.
To allow inter diffusion and improve mechanical, thermal, friction and wear properties of friction composites, homogenization treatment is carried out at 1000-1200"C for '/!> -2 hrs for iron based friction elements, whereas treatment is done at 750-950°C for '/2 -2 hrs in case of copper based friction elements. Steel cover of the capsule provides protection against oxidation during homogenization treatment & subsequent annealing treatment. Thereafter, repressing is carried out in a hydraulic press for 0-4 times.
Then, annealing is carried out at 680-950°C for 2-5 hrs for iron based friction elements and 600-850"C for '/<• -2 hrs for copper based friction elements to adjust hardness of these elements.
Finally, the cermet brakes are Machined (cutting, grinding) to size followed by drilling of holes to clamp on brake assembly. The test pieces are thus prepared.

Hot forging is one of the M •', o1 forming process where the sintered preform is hot forged. But, in the present investigation, powder mixture is forged directly under hot condition and this hot powder forging involves combined effect of compaction and sintering together, which results in final product.
The joint between friction element and backing plate is ultrasonically tested arid found much superior than that reported for the joint obtained by pressure sintering. These Trie!ion elements exhibit low wear loss, lower temperature rise, low noise level, better frictional stability i.e. stable coefficient of friction during engagement of brake. An exemplary embodiment of the present invention is described herein below:
Manufacture of iron-based friction material/brake element
For preparation of iron based friction brake element 78.5% of Fe, 6% Cu, 3% Sn, 4% SiC, 1.5% Ceramic wool, 1% CaSo4 and 6% Graphite powder

form are mixed such as herein described. The powder mix is filled in the steel capsule, with A, B, C, D and E as 45mm, 100mm, 160mm, 10mm and 15 mm respectively. Th powder filled steel capsule is kept at 1050°C for '/; hr supplying Hh gas continuously through it followed by Hot powder forging with the ram speed of 280 mm/sec and impact load of 225 tones. The forged slab so obtained is homogenized at 1050°C for V;. hr and repressed once.
This brake pad material is tested on Sub-scale Brake Inertia Dynamometer using two different kinetic energies viz. 17330 kgfm corresponding to AN32 commercial aircraft rotor brake pad application and 29158 kgfm close to Mig 27 military aircraft stator brake pad application. The test results are as follows:
(Table Remove)

Total number of cycles completed: 50 Area of each pad is about 25cm2

Interface: The same material is suitable for both the applications.
It is to be noted that the present invention is susceptible to modifications, adaptations and changes by those skilled in the art. Such variant embodiments employing the concepts and features of this invention are intended to be within the scope of the present invention, which is further set forth under the following claims:-

WE CLAIM
1. A process for manufacturing cermet friction materials/composites/brake elements with builtin backing plates comprising steps of:
preparation of a mixture comprising a mix of metals and non-metals as herein described and ceramics added with lubricants such as herein described, mixing for 2- 4 hours,
encapsulation of the mixture thus obtained in a capsule, supplied with dry Hydrogen through one of its end, other end of which is ignited to ensure dry Hydrogen atmosphere inside, the said capsule is heated at 1000-1100° for 0.5-2 hrs for iron based friction elements and at 750-900°C for 0.52 hrs for copper based friction elements,
hot forging carried out with 1-5 hammer blows in hot condition in which the ram speed and impact load is 150-350 mm/sec and 120- ns respectively for a forged slab area of 60-80 cm2,
followed by homogenization at 1000-1200°C for 0.5-2 hrs for iron based friction elements and at 750-950°C for 0.5-2hrs in case of copper based friction elements followed by repressing performed in a hydraulic press for 0-4 times,
annealing 680-950°C for 2-5 hrs for iron base friction elements and at 600-850°C for 0.5-2 hrs in case of copper based friction elements to adjust hardness of the elements.
2. A process for manufacturing cermet friction materials/composites/brake elements with builtin backing plates as claimed in claims 1, wherein constituents of the friction materials may be for example as given in Table-1