TANG XINHU (AU)
| WO2015100472A1 | 2015-07-09 | |||
| WO1998024575A1 | 1998-06-11 | |||
| WO2011094800A1 | 2011-08-11 |
| EP1715070B1 | 2012-11-07 | |||
| US20090041609A1 | 2009-02-12 | |||
| CN106756237A | 2017-05-31 |
| Claims : 1. A metal matrix composite casting comprising (a) one or more of the following host metals: titanium, zirconium, hafnium and tantalum and (b) a dispersion of refractory particles comprising two or more carbides and/or nitrides and/or borides of at least one of the host metals. 2. The casting defined in claim 1 comprises two or more carbides and/or nitrides and/or borides of one of the four host metals in a matrix of the same host metal . 3. The casting defined in claim 2 comprises two or more of titanium carbides and/or nitrides and/or borides in a titanium matrix. 4. The casting defined in claim 3 comprises titanium carbides and titanium borides in the titanium matrix. 5. The casting defined in claim 3 comprises titanium carbides and titanium nitrides in the titanium matrix. 6. The casting defined in claim 3 comprises titanium borides and titanium nitrides in the titanium matrix. 7. The casting defined in claim 1 comprises two or more carbides and/or nitrides and/or borides of one of the four host metals in a matrix of another one of the host metals . 8. The casting defined in claim 7 comprises two or more of tantalum carbides and/or nitrides and/or borides in a titanium matrix. 9. The casting defined in any one the preceding claims comprises 5-60 volume % refractory particles dispersed in the host metal matrix. 10. The casting defined in any one of the preceding claims comprises 5-40 volume % refractory particles dispersed in the host metal matrix. 11. The casting defined in any one of the preceding claims comprises greater than 10 volume % refractory particles dispersed in the host metal matrix. 12. The casting defined in any one of the preceding claims comprises greater than 15 volume % refractory particles dispersed in the host metal matrix. 13. The casting defined in any one of the preceding claims less than 30 volume % refractory particles dispersed in the host metal matrix. 14. The casting defined in any one of the preceding claims less than 25 volume % refractory particles dispersed in the host metal matrix. 15. The casting defined in any one of the preceding claims comprises less than 20 volume % refractory particles dispersed in the host metal matrix. 16. The casting defined in any one of the preceding claims comprises refractory particles in a range of 5 wt.% to 65 wt.% of the total weight of the casting. 17. The casting defined in any one of the preceding claims comprises refractory particles in a range of 12 wt.% to 25 wt.% of the total weight of the casting. 18. The casting defined in any one of the preceding claims comprises refractory particles less than 400 microns in a major dimension. 19. The casting defined in any one of the preceding claims comprises refractory particles less than 200 microns in a major dimension. 20. The casting defined in any one of the preceding claims comprises refractory particles less than 150 microns in a major dimension. 21. The casting defined in any one of the preceding claims comprises refractory particles less than 100 microns in a major dimension. 22. The casting defined in any one of the preceding claims comprises refractory particles less than 50 microns in a major dimension. 23. The casting defined in any one of the preceding claims wherein the concentrations of at least two of carbon, boron, and nitrogen is up to 10 wt.% of the total weight of the casting. 24. The casting defined in any one of the preceding claims wherein the concentrations of at least two of carbon, boron, and nitrogen is less than 8 wt.% of the total weight of the casting. 25. The casting defined in any one of the preceding claims wherein the concentrations of at least two of carbon, boron, and nitrogen is less than 7 wt.% of the total weight of the casting. 26. The casting defined in any one of the preceding claims wherein the concentrations of at least two of carbon, boron, and nitrogen is less than 6 wt.% of the total weight of the casting. 27. The casting defined in any one of the preceding claims wherein the host metal is a pure metal. 28. The casting defined in any one of claims 1 to 26 wherein the host metal is a commercial grade metal, i.e. a metal that is not 100% pure metal but is substantially pure metal . 29. The casting defined in any claim 28 wherein the host metal is Grade 12 titanium. 30. The casting defined in any one of the preceding claims formed as a casting of the material . 31. The casting defined in any one of the preceding claims formed as a component that is used in HPAL plants that are exposed to mineral slurries at high temperatures and pressures that require thermal shock resistance, erosion resistance, and corrosion resistance. 32. A method of forming a metal matrix composite material casting comprising the steps of: (a) forming a liquid melt of at least one of the host metals titanium, zirconium, hafnium and tantalum and at least two of carbon, boron, and nitrogen; and (b) forming casting of a component from the liquid melt having a required shape, with the solidified component having a microstrueture comprising a dispersion of two or more of carbides and/or nitrides and/or borides of the host metal dispersed in a matrix of the host metal . 33. The method defined in claim 32 includes forming the liquid melt of at least one of the host metals and at least two of carbon, boron, and nitrogen at furnace temperatures of less than 2000°C. 34. The method defined in claim 32 or claim 33, wherein the liquid melt comprises titanium, carbon, and boron, the microstructure of the casting comprises titanium carbides and titanium borides dispersed in a titanium matrix, with the carbides and the borides precipitating from the liquid melt during solidification of the casting. 35. The method defined in any one of claims 32 to 34 comprises mixing feed materials containing at least one of the host metals and at least two of carbon, boron, and nitrogen. 36. The method defined in claim 35 wherein the feed materials are in the form of powders and sponge. 37. The method defined in any one of claims 32 to 36 comprises pressing the mixture of the feed material and forming pellets , compacts , or other pressed shapes . 38. The method defined in any one of claims 32 to 37 comprises forming the liquid melt of at least one of the host metals and at least two of carbon, boron, and nitrogen by melting the feed material in a furnace under inert atmosphere or vacuum conditions . 39. The method defined in any one of claims 32 to 38 comprises casting with a centrifugal system. 40. A metal matrix composite material casting comprising particles of carbides and/or nitrides and/or borides of any one or more than one of the host metals titanium, zirconium, hafnium, and tantalum dispersed in a matrix of at least one of the host metals . 41. A metal matrix composite material comprising particles of carbides and/or nitrides and/or borides of any one or more than one of the host metals titanium, zirconium, hafnium, and tantalum dispersed in a matrix of at least one of the host metals . 42. A metal matrix composite material comprising particles of two or more carbides and/or nitrides and/or borides of any one or more than one of the host metals titanium, zirconium, hafnium, and tantalum dispersed in a matrix of at least one of the host metals . |
FIELD OF THE INVENTION The present invention relates to castings of
corrosion resistant and wear resistant metal matrix composite materials.
The present invention also relates to methods of casting metal matrix composite materials.
BACKGROUND
The metal matrix composite material castings of the present invention are particularly suitable for use as components that require a combination of severe corrosion resistance and wear resistance.
Examples of suitable components include, by way of example, components in High Pressure Acid Leaching (HPAL) plants that are exposed to highly corrosive and erosive mineral slurries transported in HPAL plants under high temperature and pressure conditions . These components include by way of example agitator blades. These
components also include by way of example the internal parts of valves , i.e. collectively referred to as valve trim, for conveying slurries typically at temperatures up to 200-250 °C at pressures up to 5 MPa and velocities as high as 340 m/s in HPAL plants. The high temperatures and pressures in HPAL plants significantly increase the corrosiveness of the mineral slurries . The entrained solids in the mineral slurries and the high velocities cause erosion of exposed surfaces of agitator blades, internal parts of valves and other components that are in contact with the mineral slurries . The overall effect of these conditions is a high wear rate of exposed surfaces of internal parts of these components.
In summary, the agitator blades, internal parts of valves and other components in contact with the above- described mineral slurries in HPAL plants require thermal shock resistance, erosion resistance, and severe corrosion resistance .
These components in HPAL plants are typically manufactured from (a) refractory materials selected from tungsten carbide, silicon carbide and partially stabilised zirconia (PSZ) , by sintering, (b) alloys including cobalt based alloys (such as Alloy 6) , and (c) hardfaced titanium alloys . The plants have been eager to find alternatives for these materials, because they either fail to perform satisfactorily or are too expensive.
The present invention provides an alternative to these materials. SUMMARY OF THE INVENTION
The present invention provides a metal matrix composite material casting comprising particles of carbides and/or nitrides and/or borides of any one or more than one of the host metals titanium, zirconium, hafnium, and tantalum dispersed in a matrix of at least one of the host metals .
More particularly, the present invention provides a metal matrix composite material casting comprising (a) one or more of the following host metals: titanium, zirconium, hafnium and tantalum, and (b) a dispersion of refractory particles comprising two or more carbides and/or nitrides and/or borides of at least one of the host metals.
The term "refractory particles" is understood herein to mean particles of a material with a melting point >
2900°C.
The term "host metal" used in the context of the matrix may include one of the host metals without the other host metals.
The term "host metal" used in the context of the matrix may also include an alloy of the metals titanium and/or zirconium and/or hafnium and/or tantalum. The host metal (s) may also contain small
concentrations, typically up to 6 wt.%, more typically up to 2 wt.%, of other elements either as deliberate additions or as unavoidable impurities. By way of example, the host metal (s) may also contain small concentrations of any one or more than one of aluminium, vanadium, niobium, nickel, molybdenum, chromium, and cobalt for enhanced mechanical properties and palladium, ruthenium for better corrosion performance.
It is preferred that the casting does not contain platinum group elements in concentrations greater than 0.005 wt.%.
The casting may comprise carbides and/or nitrides and/or borides of one of the four host metals in a matrix of the same host metal.
For example, the casting may comprise two or more of titanium carbides and/or nitrides and/or borides in a titanium matrix.
For example, the refractory particles may comprise titanium carbides and titanium borides in the titanium matrix .
The refractory particles may comprise titanium carbides and titanium nitrides in the titanium matrix.
The refractory particles may comprise titanium borides and titanium nitrides in the titanium matrix.
The casting may comprise two or more carbides and/or nitrides and/or borides of one of the four host metals in a matrix of another one of the host metals.
For example, the casting may comprise two or more of tantalum carbides and/or nitrides and/or borides in a titanium matrix.
The casting may comprise 5-60 volume % refractory particles dispersed in the host metal matrix.
The casting may comprise 5-50 volume % refractory particles dispersed in the host metal matrix.
The casting may comprise 5-40 volume % refractory particles dispersed in the host metal matrix. The casting may comprise greater than 10 volume % refractory particles dispersed in the host metal matrix.
The casting may comprise greater than 15 volume % refractory particles dispersed in the host metal matrix.
The casting may comprise less than 30 volume % refractory particles dispersed in the host metal matrix.
The casting may comprise less than 25 volume % refractory particles dispersed in the matrix.
The casting may comprise less than 20 volume % refractory particles dispersed in the host metal matrix.
The casting may comprise refractory particles in a range of 5 wt . % to 65 wt . % of the total weight of the casting .
The casting may comprise refractory particles in a range of 12 wt.% to 45 wt.% of the total weight of the casting .
The casting may comprise refractory particles in a range of 12 wt.% to 25 wt.% of the total weight of the casting .
The refractory particles may be less than 400 microns in a major dimension.
The refractory particles may be less than 200 microns in a major dimension.
The refractory particles may be less than 150 microns in a major dimension.
The refractory particles may be less than 100 microns in a major dimension.
The refractory particles may be less than 50 microns in a major dimension.
The refractory particles may be greater than 5 microns in a major dimension.
The concentrations of at least two of carbon, boron, and nitrogen may be up to 10 wt.% of the total weight of the casting.
The concentrations of at least two of carbon, boron, and nitrogen may be less than 8 wt.% of the total weight of the casting . The concentrations of at least two of carbon, boron, and nitrogen may be less than 7 wt.% of the total weight of the casting .
The concentrations of at least two of carbon, boron, and nitrogen may be less than 6 wt.% of the total weight of the casting .
The host metal may be a pure metal .
The host metal may be a commercial grade metal, i.e. a metal that is not 100% pure metal but is substantially pure metal .
For example, the host metal may be Grade 12 titanium. Titanium Grade 12 is a titanium grade alloy with
molybdenum and nickel that has excellent corrosion resistance in reducing and oxidising environments . The following specifications cover Titanium Grade 12: ASTM
B265 (12) , ASTM B337 (12) , ASTM B338 (12) , ASTM B348 (12) , ASTM B381 (F-12) , and UNS R53400. Titanium Grade 12 has the following nominal chemistry, in wt.%: C: 0.08% max; H: 0.015% max; Fe: 0.3% max; Mo: 0.2-0.4%; Ni : 0.6-0.9%; N: 0.03% max; O: 0.25% max; and Ti : balance.
The casting may be any suitable component having a required shape .
The component may be used as a stand-alone component or as part of a more complex component.
The component may be any component that is used in
HPAL plants that are exposed to mineral slurries at high temperatures and pressures that require thermal shock resistance, erosion resistance, and corrosion resistance. These components include by way of example agitator blades and internal parts of valves .
The present invention also provides a metal matrix composite material comprising particles of carbides and/or nitrides and/or borides of any one or more than one of the host metals titanium, zirconium, hafnium, and tantalum dispersed in a matrix of at least one of the host metals.
More particularly, the present invention also provides a metal matrix composite material comprising particles of two or more carbides and/or nitrides and/or borides of any one or more than one of the host metals titanium, zirconium, hafnium, and tantalum dispersed in a matrix of at least one of the host metals .
The present invention also provides a method of forming a metal matrix composite material casting
comprising the steps of:
(a) forming a liquid melt of at least one of the host metals titanium, zirconium, hafnium and tantalum and at least two of carbon, boron, and nitrogen; and
(b) forming a casting of a component having a required shape from the liquid melt, with the solidified component having a microstrueture comprising a dispersion of two or more carbides and/or nitrides and/or borides of the host metal dispersed in a matrix of the host metal.
The applicant has found in laboratory experimental work that it is possible to form liquid titanium melts at significantly lower temperatures when titanium is melted with at least two of carbon, boron, and nitrogen than when titanium is melted with one only of carbon, boron, and nitrogen. Specifically, the applicant found that furnace temperatures significantly higher than 2000°C were required to melt 75 wt.% Grade 12 titanium and 25 wt.% titanium carbide feed materials in an electroslag remelting furnace and that operating at these temperatures caused damage to the furnace. The applicant also found that furnace temperatures of less 2000°C could melt (a) titanium, boron and carbon feed materials, (b) titanium, boron and nitrogen feed materials, (c) titanium, nitrogen and carbon feed materials, and (d) titanium, boron, carbon, and nitrogen feed materials, without any furnace damage. In other words, operating with two or more than two of boron, carbon, and nitrogen feed materials significantly lowered the melting temperature for the materials. The applicant also found that the resultant castings formed from these feed materials had excellent corrosion resistance, hardness and other mechanical properties. The method may include forming the liquid melt of one of the host metals and at least two of carbon, boron, and nitrogen at furnace temperatures of less than 2000°C.
The furnace temperatures may be less than 1900°C, typically less than 1800°C.
In an example, where the liquid melt comprises titanium, carbon, and boron, the microstrueture of the casting may comprise titanium carbides and titanium borides dispersed in a titanium matrix, with the carbides and the borides precipitating from the liquid melt during solidification .
The method may comprise mixing feed materials containing at least one of the host metals and at least two of carbon, boron, and nitrogen.
The method may include forming a uniform mixture of the feed materials .
The feed materials may be in a sponge form.
The term "sponge form" is understood herein to mean that the feed materials are in a porous form.
The feed materials may be in the form of powders.
The term "powders" is understood herein to mean a dry, bulk solid composed of a large number of fine particles that may flow freely when shaken or tilted.
The feed materials may be in the form of powders of the host metal.
The feed materials may be in the form of powders of the host metal and one or more of carbon, boron and nitrogen.
For example, the feed materials may be titanium boride powders .
The feed materials may be in the form of powders of two or more of carbon, boron and nitrogen.
For example, the feed material may be a boron-carbon- containing powder or a boron-carbon-nitrogen-containing powder .
The feed materials may comprise up to 10 wt.% of at least two of carbon, boron, and nitrogen. The feed materials may comprise up to 10 wt.% of at least two of carbon, boron, and nitrogen.
The feed materials may comprise less than 8 wt.% of at least two of carbon, boron, and nitrogen.
The feed materials may comprise less than 7 wt.% of at least two of carbon, boron, and nitrogen.
The feed materials may comprise less than 6 wt.% of at least two of carbon, boron, and nitrogen.
The host metal may be a pure metal .
The host metal may be a commercial grade metal, i.e. a metal that is not 100% pure metal but is substantially pure metal .
For example, when the host metal is titanium, the titanium may be Grade 12 titanium.
The host metal may be an alloy of the host metal and another metal .
The method may comprise pressing the mixture of the feed material and forming pellets, compacts, or other pressed shapes .
The method may comprise forming the liquid melt of one of the host metals and at least two of carbon, boron, and nitrogen by melting the feed material in any suitable furnace under inert atmosphere conditions.
The furnace may be an electroslag re-melting furnace. The furnace may be a vacuum melting furnace.
The method may include any suitable option for casting the liquid melt into the component.
The method may comprise centrifugal casting the liquid melt into the component.
The casting may comprise 5-60 volume % refractory particles dispersed in the host metal matrix.
The casting may comprise 5-50 volume % refractory particles dispersed in the host metal matrix.
The casting may comprise 5-40 volume % refractory particles dispersed in the host metal matrix.
The casting may comprise greater than 10 volume % refractory particles dispersed in the host metal matrix. The casting may comprise greater than 15 volume % refractory particles dispersed in the host metal matrix.
The casting may comprise less than 30 volume % refractory particles dispersed in the host metal matrix.
The casting may comprise less than 25 volume % refractory particles dispersed in the matrix.
The casting may comprise less than 20 volume % refractory particles dispersed in the host metal matrix.
The casting may comprise refractory particles in a range of 5 wt . % to 65 wt . % of the total weight of the material .
The casting may comprise refractory particles in a range of 12 wt.% to 25 wt.% of the total weight of the material .
The refractory particles may be less than 400 microns in a major dimension.
The refractory particles may be less than 200 microns in a major dimension.
The refractory particles may be less than 150 microns in a major dimension.
The refractory particles may be less than 100 microns in a major dimension.
The refractory particles may be less than 50 microns in a major dimension.
The refractory particles may be greater than 5 microns in a major dimension.
The casting may comprise a uniform dispersion of the refractory particles in the host metal matrix.
The casting may comprise a non-uniform dispersion of the refractory particles in the host metal matrix.
DRAWING
The invention is described further with reference to the following Examples and the accompanying Figures, of which: Figure 1 is a micrograph of an embodiment of a titanium carbide particle/titanium host metal matrix composite material in accordance with the invention formed in laboratory work carried out by the applicant; and
Figure 2 is a micrograph of an embodiment of a titanium metal matrix composite material casting
comprising dispersions of titanium carbides and titanium borides in accordance with the invention formed in laboratory work carried out by the applicant.
EXAMPLE OF INVENTION
The applicant has carried out laboratory experimental work in relation to composite metal matrix materials in accordance with the invention formed from titanium carbide particles dispersed in a titanium host metal matrix.
The applicant has also carried out laboratory experimental work in relation to composite metal matrix material castings in accordance with the invention comprising titanium carbide and titanium boride particles dispersed in a titanium host metal matrix.
The laboratory experimental work included work in relation to composite metal matrix material castings in accordance with the invention comprising two or more of carbides and/or nitrides and/or borides of titanium dispersed in a titanium host metal matrix.
The applicant found in the laboratory experimental work that the metal matrix composite material castings tested had advantages over known ceramic materials, namely tungsten carbides, silicon carbides, and partially stabilised zirconia (PSZ) formed by sintering processes.
The findings of the laboratory experimental work are discussed below. The following description also includes two specific examples .
1. Titanium carbides, titanium borides, and titanium nitrides are chemically inert and the corrosion resistance of titanium host metal (which term includes metal alloy) has been proven in HPAL slurries under actual operating conditions — the proof is successful operation of existing valve bodies that are made from titanium Grade 12 metal (nominal chemical composition, in wt.%: Fe ≤ 0.30; O ≤ 0.18; Ti balance; C < 0.08; H < 0.15; N < 0.03; Mo 0.2- 0.4, Ni 0.6-0.9) .
2. Titanium carbides, titanium borides, and titanium nitrides are extremely hard (>2000 HV) . Also, titanium- based refractory materials including titanium carbides, titanium borides, and titanium nitrides have very similar thermal expansion coefficients as the host metal matrix material, namely titanium. This usually implies a higher resistance to thermal shock which is critical for HPAL applications, especially, when materials are used for valve trims .
3. Titanium is a tough metal .
4. Titanium metal matrix composite material castings comprising (a) hard titanium carbide particles and a tough host metal matrix of titanium Grade 12 metal or (b) hard titanium carbide/boride particles and a tough host metal matrix of titanium Grade 12 metal, have resistance to corrosion-erosion and thermal shock . These properties can be adjusted as required by changing the relative amounts of the refractory particles and the host metal matrix and other variables, such as refractory particle size and shape .
5. Titanium metal matrix composite material castings comprising dispersions of two or more than two of titanium carbides, titanium borides, and titanium nitrides have high hardness due to the particles and high toughness due to the titanium matrix and high overall corrosion
resistance . 6. Titanium carbides and titanium carbides/borides can be in situ-synthesised in titanium Grade 12 metal directly in a liquid metal manufacturing process of the applicant to ensure strong bonding between the titanium carbides and the host titanium matrix.
7. The host titanium matrix of the metal matrix composite material castings can be further optimised to increase hardness and/or corrosion resistance.
8. Chemical compositions and expected properties for titanium metal matrix composite material castings comprising dispersions of titanium carbides are as follows :
a. An example of a composition of a metal matrix composite material casting consisting of titanium carbide in a host titanium metal matrix is as follows.
b. Estimated minimum mechanical and physical properties of titanium carbide particle/titanium metal matrix composite material castings having the above composition .
Tensile Strength 538 MPa
Yield Strength 455 MPa
Coefficient of 9xl0 "6 m/m/°C @ 20-427°C
Expansion
Thermal 14 WATTS/METER-KELVIN @ Conductivity 204°C
Density 4580 Kg/m3
Melting Point 1668 °C c. Predicted performance of titanium carbide/titanium metal composite material castings in use in a HPAL plant:
• Corrosion resistance to HPAL slurry similar to that of titanium Grade 12 metal .
• Erosion resistance to HPAL slurry similar or better than that of the current valve seat constructed by Hexoloy SA insert.
• Fracture toughness greater than 50 MPa m 1'/2.
9. Chemical compositions and expected properties for titanium metal matrix composite material castings comprising dispersions of titanium carbides and titanium borides are as follows :
a. An example of a composition of a metal matrix composite material casting consisting of titanium carbide and titanium boride in a host titanium metal matrix is as follows .
b. Estimated minimum mechanical and physical
properties of titanium carbide/boride particle/titanium metal matrix composite material castings having the above composition .
Tensile Strength 600 MPa
Coefficient of 9xl0 "6 m/m/°C @ 20-427°C
Expansion
Thermal 14 WATTS/METER-KELVIN @ Conductivity 204°C
Density 4500 Kg/m3
Melting Point 2000 °C c. Predicted performance of titanium carbide and boride/titanium metal composite material castings in use in a HPAL plant:
• Corrosion resistance to HPAL slurry similar to that of titanium Grade 12 metal.
• Erosion resistance to HPAL slurry similar or better than that of the current valve seat constructed by Hexoloy SA insert
• Fracture toughness greater than 20 MPa m 1'/2.
· Erosion resistance to HPAL slurry similar or better than that of the current valve seat constructed by Hexoloy SA insert.
The experimental work carried out by the applicant indicates that the composite material castings shown in Figures 1 and 2 have very promising microstructures , mechanical properties, and foundry casting
characteristics .
As noted above, Figure 1 is a micrograph of an embodiment of a titanium carbide particle/titanium host metal matrix composite material casting in accordance with the invention formed in laboratory work carried out by the applicant .
The composite material shown in Figure 1 comprises 30 vol . % titanium carbide particles having a major diameter of approximately 15 microns and a titanium Grade 12 host metal having the nominal composition described above.
The metal matrix composite material casting was produced by casting an ingot from a titanium Grade 12 melt produced in an electric arc melting furnace under a partial pressure of argon in a water cooled copper hearth, i.e. the ingot was chill cast. The titanium carbide particles were added to the furnace melt as discrete particles having a major dimension of approximately 15 microns .
As noted above, Figure 2 is a micrograph of an embodiment of a titanium metal matrix composite material casting in accordance with the invention comprising dispersions of titanium carbides and titanium borides in a titanium matrix accordance with the invention formed in laboratory work carried out by the applicant.
The composite material casting shown in Figure 2 comprises 30 vol . % titanium carbides and titanium borides and a titanium Grade 12 host metal having the nominal composition described above.
With reference to Figure 2 , the titanium carbides precipitated as dendrites and the titanium borides precipitated as angular particles during solidification of the composite material casting.
The bulk hardness of the composite material casting shown in Figure 2 was 350HV.
The metal matrix composite material casting of Figure
2 was produced as a cast ingot from a liquid melt formed at 2000°C in an electroslag remelting furnace under inert conditions from feed materials comprising titanium Grade 12 powders and boron-carbon-containing powders.
The experimental work carried out by the applicant indicates that the composite material casting shown in Figure 2 has very promising microstruetures , mechanical properties, and foundry casting characteristics.
Many modifications may be made to the embodiments of the present invention as described above without departing from the spirit and scope of the present invention.
By way of example, having regard to the similarities of elements in the IIIB and IVB groups of the periodic table of elements, whilst the above description refers specifically to metal matrix composite material castings formed from titanium, the present invention also extends to metal matrix composite materials formed from zirconium or hafnium or tantalum or combinations of these four elements in the host metal matrix and refractory particles comprising two or more carbides and/or nitrides and/or borides of at least one of the host metals. It will be understood that the term "comprises" or its grammatical variants as used in this specification and claims is equivalent to the term "includes" and is not to be taken as excluding the presence of other features or elements .