FORM 2
THE PATENTS ACT, 1970
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
(See section 10, rule 13)
''METHOD OF MANUFACTURING METAL MATRIX CERAMIC COMPOSITES WITH IMPROVED WEAR RESISTANCE CERAMIC FORM"
AIA ENGINEERING LTD. an Indian Company of 115, G.V.M.M. Estate, Odhav Road, Ahmedabad-382 410, Gujarat,
India
The following specification particularly describes the invention and the manner in which it is to be performed.

Field of the invention
The present invention relates to a method of manufacturing metal matrix ceramic composites with improved wear resistance ceramic form. More particularly the present invention relates to a method of manufacturing metal matrix ceramic composites for wear applications in which a body comprising alumina comprising grains is formed and said body is infiltrated with molten metal.
BACKGROUND OF THE INVENTION
Minerals such as limestone coal and ores are required to be ground and powdered in various industries. Grinding mills used for this application use liners to protect mill shells and enhance performance of milling. Liners have an important influence on milling performance.
Conventional materials for producing liners are wear resistant steels and irons. In recent years metal matrix ceramic composites (MMCC) have been very successfully used for these applications. In metal matrix ceramic composites a body comprising ceramic grains is infiltrated with molten metal to form composite.
The wear life of liners depends on various factors including milling conditions. However, the material of construction of the wear part is the most important influencing factor. Metal matrix ceramic composites (MMCC) show considerably longer wear life than metallic parts.
Mill operators make continuously increasing demands on suppliers of mill liners as the quality of material being ground deteriorates. In fact such demands spurred the development metal matrix ceramic parts. Still efforts continue to improve wear life of mill liners.
Metal matrix ceramic wear part production consists of making a form or a cake of ceramic grains using a suitable binder, placing the form or cake thus formed at the mold face corresponding to wearing face of wear component and pouring liquid metal in the mold. The liquid metal penetrates the voids in the ceramic cake forming metal matrix composite. The wear life of the metal matrix composite is a very important parameter; since the mill has to be stopped each time the wear component is worn down to replace the wear component.

US Patent 6.399,176 discloses a process for manufacturing of composite wear component consisting of metal matrix whose wear surface comprising inserts being made of homogenous solid solution of 20 to 80% of alumina and 80-20% of zirconia by weight. Improved wear characteristic has been tried to achieve by the process provided in this patent. This patent teaches use of only alumina and zirconia. Further, to obtain pure alumina-zirconia homogenous solid solutions challenging and a costlier process.
US 5.143,522 discloses abrasive grain comprising about 20 to about 50 per cent by weight of zirconia. reduced titania of 1.5 to about 10 percent in weight, carbon in an amount of 0.03 to about 0.5% by weight, impurities not greater than 3% by weight and balance of alumina. The abrasive grain of this patent has a high proportion of tetragonal zirconia.
US Patent 3,181,939 discloses the process of production of fused Alumina/Zirconia grains.
US patent 5551963, teaches that ceramic grains comprising 70-96% Alumina and balance Zirconia have good abrasive properties.
US patent 5061665, have shown that Alumina/Zirconia grains produced by fusing and melting powders of two grains together with other additives can b$ used for a variety of applications including wear resistance.
Indian patent 248740 explains production of metal matrix ceramic wear parts using alumina, zirconia and titanium oxide grains, wherein alumina is in the range of 35-65 wt%. /zirconia is in the range of 30-60 wt% and titanium oxide in the range of 1-1.0 wt%.
Use of metal matrix ceramic composite (MMCC) using Alumina/Zirconia grains is well established industrial practice. It is well known that Alumina grains are harder (Moh hardness 9) but less tough than Zirconia grains and Zirconia grains are less hard (Moh hardness 8) but more tough than alumina grains. As alumina has higher hardness than zirconia, the grains with high alumina weight percentage are more fragile. Therefore to make the metal matrix composite with high alumina content with improved toughness there is a need to improve the binding between the ceramic grains and metal matrix. The present invention discloses the method of improving wear resistance of MMCC by improving the binding between the grains and matrix.

The present invention aims to provide a method and metal matrix composite with improved wear life.
OBJECTS OF THE INVENTION
The primary object of the present invention is to provide a method for manufacturing metal matrix ceramic composite which leads to improved wear resistance and an improved wear life. Yet another object of the present invention is to provide a ceramic form for use in a method of making a metal matrix ceramic wear part.
BRIEF DESCRIPTION OF THE FIGURES
Figure 1 represents the grains (1) enveloped in a layer of silicate (2) as per prior art.
Figure 2 represents a ceramic form wherein the grains (1) are enveloped in a layer of Sodium Silicate (2) with carbon particles (3) provided.
Figure 3 illustrates the MMCC, grains well in contact with metal matrix.
Figure 3 shows MMCC as per present invention comprising grains (1), infiltrated metal matrix (4) and broken glass layer (3!). It can be seen that the ceramic grains (I) are held by (4).
It may be noted that figures are schematic in nature.
SUMMARY OF THE INVENTION
Accordingly, the present invention relates to a metal matrix ceramic composite (MMCC) with improved wear resistance comprising of ceramic form, wherein the ceramic form comprising a mixture of ceramic grains comprising alumina, at least one binder and carbon particles, wherein the said ceramic form is embedded in molten metal.
In another aspect of the present invention, the metal matrix ceramic composite (MMCC) is manufactured by a method comprising the steps of: (i) forming a ceramic form by mixing a mixture of ceramic grains having alumina, at least one binder and carbon particles; (ii) placing the ceramic form as obtained in step (i), in a mould (iii) pouring molten metal over the ceramic form of step (ii) for infiltration of the molten metal into the ceramic form and forming the metal matrix ceramic composite (MMCC) with improved wear resistance.

DETAILED DESCRIPTION OF THE INVENTION
While the invention is susceptible to various modifications and alternative forms, specific aspect thereof has been shown by way of example and will be described in detail below. It should be understood, however that it is not intended to limit the invention to the particular forms disclosed, but on the contrary, the invention is to cover all modifications, equivalents, and alternative falling within the spirit and the scope of the invention.
The Applicants would like to mention that the examples are mentioned to show only those specific details that are pertinent to understanding the aspects of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having benefit of the description herein.
The terms "comprises", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a process that comprises a list of components does not include only those components but may include other components not expressly listed or inherent to such process. In other words, one or more elements in a system or process proceeded by "comprises... a" does not, without more constraints, preclude the existence of other elements or additional elements in the system or process.
Accordingly, the present invention relates to a metal matrix ceramic composite (MMCC) with improved wear resistance comprising of ceramic form, wherein the ceramic form comprising a mixture of ceramic grains comprising alumina, at least one binder and carbon particles, wherein the said ceramic form is embedded in molten metal.
In one aspect of the present invention metal matrix ceramic composite MMCC, wherein the amount of carbon particles is between 0.5 to 3.0 % by weight of total ceramic grains comprising alumina.
In another aspect of the present invention the MMCC, wherein the carbon particles have grit size in the range of 120-220.
In another aspect of the present invention the MMCC, wherein a mixture of ceramic grains comprising more than 85%, preferably more than 95% alumina.

In another aspect of the present invention the MMCC, wherein ceramic form comprises fine alumina powder of grit size 1000-1500
In another aspect of the present invention the MMCC, wherein fine alumina powder is in the range of 0.5 to 1.5% by weight of the total ceramic grains comprising alumina.
In another aspect of the present invention the MMCC, wherein the carbon particles are graphite.
In another aspect of the present invention the MMCC, wherein the graphite particles are electrode grade graphite particles.
In yet another aspect of the present invention the metal matrix ceramic composite (MMCC) is manufactured by the method comprising the steps of: (i) forming a ceramic form by mixing a mixture of ceramic grains having alumina, at least one binder and carbon particles; (ii) placing the ceramic form as obtained in step (i). in a mould (iii)pouring molten metal over the ceramic form of step (ii) for infiltration of the molten metal into the ceramic form and forming the metal matrix ceramic composite (MMCC) with improved wear resistance.
In another aspect of the present invention the method of manufacturing MMCC, wherein the amount of carbon particles is between 0.5 to 3,0 % by weight of total ceramic grains comprising alumina.
In another aspect of the present invention the method of manufacturing MMCC. wherein the carbon particles have grit size in the range of 120-220.
In another aspect of the present invention the method of manufacturing MMCC, wherein a mixture of ceramic grains comprising more than 85%, preferably more than 95% alumina.
In another aspect of the present invention the method of manufacturing MMCC, ceramic form comprises fine alumina powder of grit size 1000-1 500
In another aspect of the present invention the method of manufacturing MMCC, wherein fine alumina powder is in the range of 0.5 to 1.5% by weight of the total ceramic grains comprising alumina.

In another aspect of the present invention the method of manufacturing MMCC. wherein the carbon particles are graphite particles.
In another aspect of the present invention the method of manufacturing MMCC, wherein the graphite particles are electrode grade graphite particles.
In another aspect of the present invention the metal matrix ceramic composite (MMCC) is manufactured by the method comprising the steps of: (i) a mixture is formed comprising at least the following ingredients: (a) ceramic grains comprising alumina, (b) a binder and (c) carbon particles having a grit size preferably 120-220, (ii) The mixture is filled in synthetic rubber core boxes and the core boxes with the mixture are baked. After the baking operation, rubber core boxes are separated to get ceramic form. The ceramic form is fixed at the mold surface corresponding to the wearing surface of the casting. Construction of the ceramic form allows good infiltration by the liquid metal (iii) molten metal like iron or steel of suitable composition is poured over the ceramic form for infiltration of the molten metal into the form for forming the metal matrix ceramic composite .
Without forming a restriction of the mechanism which lies at the root of the improvement. possible explanations for the effect are:
Manufacturing process of metal matrix ceramic parts involves production of ceramic forms/cakes. Sodium silicate is usually used as binder of the grains. After pouring of liquid metal, the metal infiltrates the pores in the ceramic form to form the metal matrix ceramic composite. During this process the binder, usually Sodium silicate, forms a surface layer of glass on the grains. This glass layer cannot help to limit fragility of Alumina comprising grains. The grains would perform better if the grains can be more rigidly held by the metal matrix.
Another problem is differential expansion and contraction characteristics of alumina and metal. If a soft buffer material is provided between metal and ceramic grain the differential expansion could be accommodated
The use of carbon particles provides an improvement in life time.
The present invention is particularly advantageous when the total alumina content in the cake is more than 85% and preferably more than 95%.

Wear life of MMCC can be improved if harder grains can be used. Alumina grains are harder than alumina/zirconia grains but more fragile. The new grains improve wear life of MMCC substantially. Thus the use of carbon particles provides for the possibility of using high alumina grains thus further improving life time. The invention is thus particularly advantageous when total alumina content in the cake is more than 85% and preferably more than 95%. Use of nearly pure Alumina grains in combination with the use of carbon particles provides stronger binding of alumina grains by metal matrix. The carbon particles provide a mechanism of breaking silicate glass barrier between metal and ceramic grains. In addition a compatible buffer is provided between metal and ceramic grains to allow differential expansion,
The amount of powder carbon particles is preferably between 0.5 to 3.0 % of total alumina comprising ceramic grains in weight percentage.
Preferably fine alumina powder with a grit size of between 1000 - 1500 grit size is used in the mixture, preferably in a weight percentage of between 0.5 to 1.5% of total alumina comprising ceramic grains.
The life time is improved by improving the binding of the alumina comprising grains to the metal matrix.
The inventor has considered using an agent to develop stronger binding between ceramic grains and metal matrix.
The selected material should preferably satisfy the following criteria:
- The agent preferably is compatible with liquid metal
- The agent preferably withstands temperature up to 1500 ° C
- The agent preferably provides cushioning effect during differential expansion
- The agent preferably has good thermal conductivity
- It preferably assists in breaking silicate glass layer
Different materials were considered for experiments. Carbon particles gave best results and experiments were performed using carbon particles.

The size of carbon particles to be employed was a further feature considered by inventor. Carbon particles are preferably in the size range of grit sizes 120 to 220.
Within this range a good dispersion of the carbon particles can be obtained while an effective breaking of the glass layer is achieved.
The invention has a positive effect when using various alumina comprising grains, including alumina/zirconia ceramic grains, for instance comprising up to 15% zirconia.
A further consideration, for a preferred embodiment of the invention, is the choice of alumina comprising grains.
Preferably alumina grains in the grit size range of 6 to 12 are used. The grains may contain up to 5% MgO and other impurities.
in particular it is advantageous to use alumina grains comprising 95% or more alumina. Use of 95% or higher purity Alumina grains in combination with the use of carbon particles provides alumina grains rigidly bound and held by metal matrix. The carbon particles provide a mechanism of breaking silicate glass barrier between metal and ceramic grains. The carbon is absorbed in the surrounding metal matrix. In addition a compatible buffer is provided between metal and ceramic grains to allow differential expansion.
It has been found that using the combination of carbon particles and alumina comprising grains comprising less than 15% of other oxides provides for increase in life time by about 25%, compared to using conventional alumina/zirconia grains, with more than 20% zirconia .
Pine Aluminum oxide powder is added in the range of grit sizes 1000 - 1500 to improve moldability.
The ceramic ingredients used in examples were as follows:-
A mixture of Alumina grains, containing at least 85 %, preferably at least 95% Al203 by weight, balance being impurities like Magnesium oxide (MgO) and others, size range of particles being 6 to 12 grit sizes. The mixture in embodiments is more or less homogeneous mixture, i.e. all grains but for possibly a small percentage (10%) or less in weight%) having less than the indicated weight percentage of alumina, and even all ceramic grains being substantially the same

(meaning a standard spread in weight percentage alumina over the grains being on average 5% or less, preferably 2% or less), but embodiments can also be formed by a mixture wherein the alumina content may show a variation over the ceramic grains, the average percentage of alumina being more than the indicated weight percentage of 85%. preferably 95%. Carbon particles preferably in the size range 120-220 grit sizes. Carbon particles are added between 0.5 to 3.0 % of total ceramic particles.
Preferably graphite is used, most preferably electrode grade graphite (EGG). EGG has the advantage over natural graphite that it is easier to form a powder of controlled grit size of it. Thus the use of electrode grade graphite forms a feature of a preferred embodiment of the invention. Other types of soft carbon that could be used are types of carbons such as charcoal, coal (anthracite, lignite etc), carbon black and soot. Graphite is preferred for its purity over such other types of soft carbons.
Optionally fine Alumina powder in the range of grit sizes 10C)0 - 1500. Fine Alumina powder is added between 0.5 to 1.5% of total ceramic particles.
The method is not restricted to any manner as to how the ingredients are mixed, in particularly not with respect as to the order in which ingredients of the mixture are added to the mixture.
The first step in forming a Metal Matrix Ceramic Composite (MMCC) wear part is formation of cake/form. Ceramic ingredients, as above, are mixed with a suitable binder, specifically Sodium Silicate. The binder is preferably added to the extent of approximately 5% by weight. The mixture is poured in rubber core boxes having shape that will give ceramic cake of desired shape and size. Carbon Dioxide gas is passed over the filled box to develop adequate strength for handling. Ceramic form with rubber core box is baked for example between 100 and 225 "C, preferably between 100 to 125 C, for 2 to 4 hours. The cakes are stripped from core boxes and are ready for use. The temperature range between 100 and 125 °C is preferred. Compared to using a temperature above 125 C, the risk of that carbon particles react with oxygen in oven atmosphere and getting damaged is reduced.
Molds are produced using standard foundry practices. Cerarnic cakes are located at surfaces of molds corresponding to wear surfaces of castings being produced. Liquid metal composition is

chosen taking in to account impact conditions of application. Both iron and steel can be used in
the process.
iron composition may contain alloying in the following range:-
C 1 to 3.5%, Cr 11 to 28%, with required alloy additions such as Mo. Ni, and Cu
Steel composition may contain alloying in the following range:-
C 0.2 to 1%, Cr 1 to 4%. with other alloying such as Mn, Mo and Ni as required.
Liquid metal is poured in the molds and after allowing adequate cooling time the molds are disturbed. Castings have integral MMCC portion.
EXAMPLES
Following examples are given by way of illustration therefore should not be construed to limit the scope of this invention.
The introduction of carbon particles has shown to provide a remarkable improvement in life time of the metal matrix ceramic composite, as is apparent from below given examples.
Wear parts for two different types of mill were produced and installed in the mills. The results are given below.
EXAMPLE 1
An experiment was performed on a hammer mill used to crush limestone. Metal Matrix Ceramic Composite (MMCC) wear parts were produced using technology as per the present invention. Steel with 0.42% C, 3.2% Cr, 0.53% Mo, 0.37% NL 0.75% Mn, 0.66% Si composition was used. The experiment showed 35% improvement in lifetime of the wear part over conventionally manufactured MMCC, i.e. without addition of carbon particles (graphite powder), MMCC wear parts comprising alumina/zirconia (in the ratio of approximately 60/40%) grains in the same mill.
EXAMPLE 2
Another experiment was conducted in a crusher mill with grinding element called blow bars. MMCC wear parts were produced using technology as per the present invention. Cast iron with

composition 2.88% C, 29.32% Cr, 0.42% Mo, 0.62% Mn, 0.81% Si was maintained. The experiment showed 27% improvement in lifetime of the wear part over conventionally manufactured MMCC wear parts comprising alumina/zirconia in the mentioned ratio in the same mill.
Thus, the results shows substantial improvement compared to using conventional alumina-zirconia grains. Further, using alumina grains has an advantage that alumina grains are manufactured in a manner which is less taxing to the environment, in particular less energy and resources are needed to produce alumina grains as compared to alumina/zirconia grains. Thus, apart from improving the life time of the wear part, which is an advantage for any alumina comprising grains, the above embodiment of the invention in which alumina grains are used with a very high (above 85%, preferably above 95%) percentage of alumina, has the added advantage, as compared to using conventional alumina/zirconia ceramic grains, that the environment is less taxed.
The invention is not restricted to the above given examples.
All grit sizes are Federation of European Producers of Abrasives (FEPA ) Standard 42-1 & 42-2 (2006) grit sizes.
The FEPA standard specifies the mean sizes associated with the mentioned grit sizes as follows:
Grit Size Size (microns) (mean)
6 3460
12 1765
120 109
220 58
1000 4.5
1500 2.0

The mean diameters of grits shown in the table are estimated and given for ease of providing information; the FEPA-Standard defines grit sizes in terms of a range and not a single value.
The word "comprising" in a claim does not exclude the use of further ingredients or features, although, preferably, the mentioned ingredients form 85% or more, most preferably 95% or more of the mixture.
The word "a" or "an" before a feature in the claim does not exclude the use of two or more of the said feature. A reference to a feature by means of using "the" before the feature also does not form a restriction to only one of such a feature, unless specifically mentioned.

WE CLAIM
1. A metal matrix ceramic composite (MMCC) with improved wear resistance comprising of ceramic form, wherein the ceramic form comprising a mixture of ceramic grains comprising alumina, at least one binder and carbon particles, wherein the said ceramic form is embedded in molten metal.
2. The metal matrix ceramic composite (MMCC) as claimed in claim 1, wherein the amount of carbon particles is between 0.5 to 3.0 % by weight of total ceramic grains comprising alumina.
3. The metal matrix ceramic composite (MMCC) as claimed in claim I. wherein the carbon particles have a grit size in the range of 120-220.
4. The metal matrix ceramic composite (MMCC) as claimed in claim 1, wherein a mixture of ceramic grains comprising more than 85%. preferably more than 95% alumina.
5. The metal matrix ceramic composite (MMCC) as claimed in claim 1, wherein the ceramic form comprises fine alumina powder of grit size 1000-1500.
6. The metal matrix ceramic composite (MMCC) as claimed in claim lor 5, wherein fine alumina powder is in the range of 0.5 to 1.5% by weight of the total ceramic grains comprising alumina.
7. The metal matrix ceramic composite (MMCC) as claimed in claim 1, wherein the carbon particles are graphite particles.

8. The metal matrix ceramic composite (MMCC) as claimed in claim 1 or 7, wherein the graphite particles arc electrode grade graphite particles.
9. The metal matrix ceramic composite (MMCC) as claimed in claim 1 is manufactured by the method comprising the steps of:
(i) forming a ceramic form by mixing a mixture of ceramic grains having
alumina, at least one binder and carbon particles; (ii) placing the ceramic form as obtained in step (i). in a mould (iii) pouring molten metal over the ceramic form of step (ii) for infiltration of the molten metal into the ceramic form and forming the metal matrix ceramic composite (MMCC) with improved wear resistance.
10. The metal matrix ceramic composite (MMCC) as claimed in claim 9 wherein the amount of carbon particles is between 0.5 to 3.0 % by weight of total ceramic grains comprising alumina.
11. The metal matrix ceramic composite (MMCC) as claimed in claim 9 wherein the carbon particles have a grit size in the range of 120-220.
12. The metal matrix ceramic composite (MMCC) as claimed in claim 9 wherein a mixture of ceramic grains comprising more than 85%, preferably more than 95% alumina.
13. The metal matrix ceramic composite (MMCC) as claimed in claim 9, wherein the ceramic form comprises fine alumina powder of grit size 1000-1500.
14. The metal matrix ceramic composite (MMCC) as claimed in claim 9 or 13 wherein fine alumina powder is in the range of 0.5 to 1.5% by weight of the ceramic grains comprising alumina.

15. The metal matrix ceramic composite (MMCC) as claimed in claim 9 wherein the carbon particles are graphite particles.
16. The metal matrix ceramic composite (MMCC) as claimed in claim 9 or 15 wherein the graphite particles are electrode grade graphite particles.
17. Hammer mill part comprising a metal matrix ceramic composite (MMCC) manufactured by any of the methods as claimed in claims 9 to 16.
18. Crusher mill part comprising a metal matrix ceramic composite (MMCC) manufactured by any of the methods as claimed in claims 9 to 16.