FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
(See section 10, rule 13)
"IMPROVED WEAR RESISTANT METAL PARTS AND METHOD OF MANUFACTUEE THEREOF"
AlA ENGINEERING LTO. an Indian Company of 115, G.V.M.M. Estate, Odhav Road, Ahmedabad-38241,, 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 provides an improved wear resistant metal part. More particularly, the present invention provides an improved wear resistant metal part with mineral grains embedded therein on the wearing surface. The present invention also relates to a method for the manufacture of wear resistant metal parts by embedding mineral grains therein on the wear surface.
The present invention particularly relates to composite wear components manufactured by casting. Such wear components conventionally have a metal matrix whose wear face is provided with inserts to enhance the wear resistant characteristics. BACKGROUND OF THE INVENTION
The use of porous abrasives to improve mechanical grinding processes is generally well known. Pores typically provide access to grinding fluids, such as coolants and lubricants, which tend to promote more efficient cutting, minimize metallurgical damage (e.g., surface burn), and maximize tool life. Pores also permit the clearance of material (e.g., chips or swarf) removed from an object being ground, which is important especially when the object being ground is relatively soft or when surface finish requirements are demanding (e.g., when back grinding silicon wafers).
Previous attempts to fabricate abrasive articles and/or tools including porosity may generally be classified into one of two categories;. In the first category, a pore structure is created by the addition of organic pore inducing media (such as ground walnut shells) into the abrasive article. These media .thermally decompose upon firing, leaving voids or pores in the cured abrasive tool. Examples of this category are U.S. Pat. No. 5,221,294 to Carmen, et al., and U.S. Pat. No. 5,429,648 to Wu, and Japan Patents A-91-161273 to Grotoh, et al., A-91-281174 to Satoh, et al. In the second category, a pore structure may be created by the addition of closed cell materials, such as bubble alumina, into an abrasive article. See for example U.S. Pat. No. 5,203,886 to Sheldon, et al.
In an alternative approach, Wu et al., in U.S. Pat, Nos. 5,738,696 and 5,738,697, each of which is fully Incorporated herein by reference, disclose an abrasive article and method for fabricating the same including fiber-like abrasive grains having a length to diameter aspect ration of at least 5:1. The poor packing characteristics of the elongated abrasive grains resulted in an abrasive article including increased porosity and permeability and suitable for relatively high-performance grinding.

US Patent 6,755,729 discloses an abrasive article including from about 40 to about 80 volume percent interconnected porosity, the article being useful as a segment for a segmented grinding wheel, and a method for fabricating the same. The method includes blending a mixture of abrasive grain, bond material and dispersoid particles, the mixture including from about 40 to about 80 volume percent dispersoid particles. In one embodiment the mixture includes from about 50 to about 80 volume percent dispersoid particles. In another embodiment the mixture includes an organic bond material and from about 40 to about 80 volume percent dispersoid particles. The powder mixture is then pressed into an abrasive laden composite and thermally processed. After cooling the compostte is immersed into a solvent, which dissobves substantially all of the dispersoid particles, leaving a highly porous, bonded abrasive article.
US Patent 6,749,653 discloses an abrasive article comprising a binder and a plurality of abrasive particles, wherein at least a portion of the abrasive particles are abrasive particles comprising at least 65.0 percent by weight sint~red, polycrystalline zirconia, based on a total weight of the abrasive particle; wherein said abrasive article is selected from the group consisting of coated abrasive articles, bonded abrasive articles, non-woven abrasive articles, and abrasive brushes.
US Patent 5,552,353 discloses a process for the synthesis of homogeneoss advanced ceramics such as SiC+AIN, SiAION, SiC+Al203, and Si3N4 +AlN from natural clays such as kaolin, halloystte and montmorillonite by an intercalation and heat treatment method. Included are the steps of refining clays, intercalating organic compounds into the layered structure of clays, drying the intercalated mixture, firing the treated atmospheres and grinding the loosely agglomerated structure. Advanced ceramics produced by this proceduee have the advantages of homogeneity, cost effectivenes,, simplicity of manufacture, ease of grind and a short process time. Advanced ceramics produced by this process can be used for refractory, wear part and structure ceramics. The wear parts obtained are homogeneous in nature.
The inclusion of grains into wear parts is known in the art. Conveniion~l hard metal materials used to provide wear resistance to the underlying steel substrate usually comprises pellets or particles of cemented tungsten carbide (WC-Co) and/or cast carbide particles that are embedded or suspended within a steel matrix. The carbide materials are used to impart properties of wear resistance and fracture resistance to the steel matrix. Conveniionll hard metal materials useful for forming a hard faced layer on bits may also include one or more alloys to provide one or more certain desired physical properties. As mentioned above, the hard faced layer is bonded or applied to the underlying steel teeth by a welding process. '

The ha d faced layer is conventionally applied onto the milled teeth by oxyacetylene or atomic hydrogen welding. The hard facing process makes use of a welding "rod" or stick that is formed of a tube of mild steel sheet enclosing a filler which is made up of primarily carbide particles. The filler may also include deoxidizer for the stee,, flux and a resin binde.. The relatively wear resistant filler material is typically applied to the underlying steel tooth surface, and the underlying tooth surface is thus hard faced, by melting an end of the rod on the face of the tooth. The steel tube melts to weld to the steel tooth and provide the matrix for the carbide particles in the tube. The deoxidizer alloys with the mild steel of the tube.
This hard facing process is effective for providing a good bond between the steel substrate and conventionll hard metal materia.. However, it is a relatively crude process that is known to adversely impact performance properties of the hard faced layer. The hard facing welding process itself generates certain welding byproducts that can and do enter the applied material to produce an inconsistent material micro;structure. For example, the welding process is known to introduce oxide inclusions and h-phases into the applied material, which then disrupt the desired material microstructure. Such disruptions or inconsistencies in the material microstructure are known to cause premature chipping, flaking, fracturing, and ultimately failure of the hard faced layer. Additionally, the welding process and associated thermal impact thereof can cause cracks to develop in the material microstructure, which can also cause premature chipping, flaking, fracturing, and ultimately failure of the hard faced layer.
Additionally, the hard facing process of welding the carbide-containing steel material onto the underlying substrate makes it difficult to provide a hard faced layer having a consistent coating thicknes,, which ultimately governs the rate of wear loss for the steel material, and the related service life of bit.
Examples uf conventionll hard metal materials, useful for forming a conveniionll hard faced layer, typically comprise in the range of from about 30 to 40 percent by weight steel, and include carbide pellets and/or particles having a particle size in the range from about 200 to 1,000 micrometers. Examples of conventional materials used for forming hard faced layers can be found in U.S. Pat. Nos. 4,944,774; 5,663,512; and 5,921,330.
The combination of relatively high steel content and large carbide" particle size for such conventional hard metal materials dictate that the mean spacing between the carbide pellets within the steel matrix be relatively large, e.g., greater than about 10 micrometers. It is believed that this relatively large mean spacing of carbide particles within the conveniionll hard metal material causes preferential wear of the steel matrix that is known to lead to uprooting and removal of the carbide particles. Such wear loss is known to occur along the

milled tooth tip at high stress locations during drilling and funciiont to accelerate loss ot the hard facing, which is a predominant failure mechanism for hard faced btt surface,, thereby limiting the service life of such bits.
Another significant problem faced with wear components of the type desciibed above is that a balance has to be drawn between the desired properties of ductility and resistance to abrasion. The common solution in the art is to provide a ductile metal part with wear inserts on the wearing face to impart toughness and abrasion resistance. The prior art has focused on improving wear resistance by improving the nature of the inserts. OBJECTS OF THE INVENTION
The main object of the invention is to proVide an improved wear resistant metal par..
It is another object of the invention to provide a method for the manufacture of an improved wear resistant metal part.
Another object of the invention is to provide a method for improving wear characteristics of metallic parts used by various industries like cement, mining and thermal power. SUMMARY OF THE INVENTION
The invention accordingly provides a method for the manufacture of a wear resistant metallic part comprising introducing mineral grains at the wearing surface, said mineral grains comprising a mixture of zirconia, alumina and titanium oxide.
In one embodiment of the invention, the mixture comprises alumina, alumina/zirconia eutectic and titanium oxide.
In another embodiment of the invention, :he mineral grains are introduced into the wearing face of the metallic part by forming cakes of the desired shape, said cakes being imparted strength by addition of fine Aluminium Oxide powder along with Sudium Silicate.
In another embodiment of the invention, the mixture of mineral particles, Alumina powder and an organic or inorganic binder is filled in boxes of suitable shapes and optionally treated with gases, to develop adequate strength.
In another embodiment of the invention, the cakes are heated to a temperature between 80 -220°C.
In anothe: embodiment of the invention, the cakes are placed on the interior surface of a refractory mould or metallic die, and then liquid metal is poured into the cavity the liquid metal composition beiag selected to achieve complete intermixing of mineral grains and metal, the metallic die/mould being then disturbed after cooling and the wear parts then

removed and subjected to a heat treatment to provide wear resistance and toughness to the metallic portion.
In another embodiment of the invention, the mletallic part comprises a grinding roll for a thermal power station.
In another embodiment of the invention, in$erts are provided in the metallic die, followed by pouring of iron into the die to develop Ithe composite casting, the casting thus obtained being heat treated to improve wear resistance and toughness.
In another embodiment of the invention, the metallic wear part is a table liner for a vertical mill, said method comprising introducing cakles of mineral grains at the wear surface of the part of the casting, the casting being produced by a conventional foundry casting process, the casting thus obtained being heat treated iand machined to impart toughness and improve wear resistance. DETAILED DESCRIPTION OF THE INVENTION
The present invention has succeeded in improving wear characteristics of metallic parts used by various industries like cement, mining and thermal power. The improvement has been achieved by introducing mineral grains at the wearing surface. Minerals which have been proved to improve the wear resistance have been identified as Zirconia, Alumina and Titanium Oxide.
After trials with various combinations of mineral grains, it was found that most optimum wear characteristics were observed with mineral grains which are mixture of Alumina, Alumina/Zirconia eutectic and Titanium Oxide. This mixture is more economical than pure Alumina-Zirconia homogeneous solid solutions. The size of the grains is decided by thickness of the wear zone required. Besides, pure alumina-zirconia homogenous solid solutions are not technically feasible.
In order to be able to introduce such grains at desired locations, it is necessary to form cakes of required shape. Moreover, such cakes have to possess adequate strength to withstand eventual engulfing by liquid metal. Addition of very fine Aluminium Oxide powder along with Sodium Silicate is aimed to achieve high strength. Addition of fine Aluminium Oxide powder imparts thixotropic properties and improves wear resistance. The mixture of previously described mineral particles, Alumina powder and organic or inorganic binder filled in boxes of suitable shapes and treated with gases, if required, to develop adequate strength for handling. After removing the cakes from the boxes, the same are heated to temperature between 80 - 220°C so that adequate strength is developed.

The cakes are located at desired surfaces of refractory moulds or metallic dies. After closing the mould assemblies/die assemblies, liquid metal is poured into the cavity. The liquid metal composition is so selected to achieve complete intermixing of mineral grains and metal. The moulds/ dies are disturbed after adequate cooling time and the wear parts thus produced are subjected to special heat treatment so that metallic portion develops better wear resistance and toughness.
The ceramic grains used in the invention comprise 35-65% by weight of aluminium oxide, 30-60% by weight of zirconium oxide and 1-10% by weight of titanium oxide.
More preferably, the amount of aluminum oxide is in the range of 51 to 53% by weight, the amount of zirconium oxide is in the range 43-46% by weight and titanium oxide is in the range of2-4% by weight. Example 1:
A wear part described as grinding roll used by thermal power stations was produced using the above process. The manufacturing sequence involved production of cakes of mineral grains, introduction of the cakes and production of composite castings called inserts, location of inserts in the metallic die, pouring of iron in to the die to develop composite casting. The casting thus produced was heat treated and tried in wear application. It was observed to improve the life of wear components substantially. Example2:
Another wear part described as table liner for vertical mill was produced following the method of Example 1. Cakes of mineral grains were introduced at the wear surface of the part of the casting; The casting was produced using conventional foundry casting process. The casting was heat treated and machined and xied for wear characteristics. Significant improvement was noticed in the wear chnracteristic.
It must be understood that modification and variations of the disclosure presented above are possible without departing from the spirit and scope of the invention and are intended to be covered therein.

WE CLAIM:
11 A method of manufacturing a wear reslstant metallic part, said method comprising the steps of introducing mineral grains at the wearing surface, said mineral grains comprising a mixture of aluminium oxide (alumina) in the range of 35-65% by weight, zirconium oxide (zirconia) in the range of 30-60% by weight, tttanium oxide in the range of 1-10% by weight and a minor amount of sodium silicate.
2. A method as claimed in claim 1, wherein the said mixture of aluminium oxide in the range of 51-53% by weight, the amount of zirconium oxide in the range of 43-46% by weight and titanium oxide in the range of 2-4% by weight.
3. A method as claimed in claim 1, wherein the mixture comprises alumina, alumina/zirconia eutectic and titanium oxide.
4. A method as claimed in claim 1, wherein the mineral grains are introduced into the wearing face of the metallic part by forming cakes of the desired shape, said cakes being imparted strength by addition of fine aluminium oxide powde..
5. A method as claimed in claim 4, whereir the mixture of mineral particles, alumina power and an organic and inorganic binder is filled in boxes of suitable shapes and optionally treated with gases, to develop adequate strength.
6 A method as claimed in claim 5 wherein the cakes are heated to a temperature
between 80-220°C.
7. A method as claimed in claims 4 to 6, whereii the cakes are placed on the interior
surface of a refractory mould or metaliic die, and then liquid metal is pourei into the cavity, the liquid metal composition being selected to achieve complete intermixing of mineral grains and meta,, the metallic die/mould being then

disturbed after rooling and the wear parts then removed and subjected to a heat treatment to provide wear resistance and toughness to the metallic portion.
88 A meehod as slaimed in any of the preceding claims, wherein the metallic part is a
part tof grinding roll used in a thermal power station.
99 A method as claimed in claim 8, wherein inserts are provided in the metallic die, followed by pouring of iron into the die to develop the composite casting, the casttng thus obtained being heat treated to improve wear resistance and toughness.
110 A method as claimed in claims 1 to 7, wherein the metallic wear part is a table llner for a vertical mill, said method comprising introducing cakes of mineral grains at the wear surface of the part of the carting, the casting being produced by a conventional foundry casting process, the casting thus obtained being heat treated and machined to impart toughness and improve wear resistance.
111 A composite wear component prepared by the method of any preceding claims comprising a metallic body with one or more: working faces, said working faces being provided with mineral grains comprising a mixture of aluminium oxide (alumina) in the range of 35-65% by weight, zirconium oxide (zirconia) in the range of 30-60% by weight, titanium oxide in the range of 1-10% by weight and a minor amount of sodium silicate.

12. A composite wear component as claimed in claim 11, wherein the mineral grains are provided in the form of inserts.
13. A composite wear component as claimed in claim 11 or 12, whereit the mineral grain comprises a mixture of alumina, alumina/zirconia eutectic and titanium oxide.

14. A composite wear component as claimed in claims 11 to 13, wherein fine aauminium oxide powder is optionally added.
15. A composite wear component as claimed in claim 11, wherein the amount of aluminium oxide is in the range of 51-53% by weight, the amount of zirconium oxide iisn the range 43-46% by weight, titanium oxide is in the range of 2-4% by weight and minor amount of sodium silicate.
116 A method for the manufacture of a wear resistant metallic part substantially as described hereinbefore and with reference to the foregoing examples.
17. A wear component substantially as described hereinbefore and with reference to the foregoing examples.