Functionally Graded Matrix Alloy And Method of Fabricating Metal Matrix Composites

Description

BACKGROUND OF THE INVENTION

The present disclosure relates generally to alloy formulations in nickel metal matrix composites and methods of manufacturing the nickel metal matrix composite. The alloy formulations are appreciably higher strength and creep resistance as compared to conventional nickel-based superalloys without any increase in weight. The disclosed nickel metal matrix composite has a structural use above 1800° F. using economical and commonly available metallic foil.

Nickel-based superalloys have great heat and oxidation resistance. Although superior to other metallic alloys, at temperatures above 1800° F., they lose significant strength. Refractory elements, such as niobium or tungsten based alloys, maintain their strength and creep strength above 2200° F. However, refractory elements have poor oxidation resistance, are appreciably heavier, and are much more expensive to manufacture and recycle than nickel-based alloys. Ceramic Matrix Composites and Carbon-Carbon Composites maintain their strength to appreciably higher temperatures, but they lack sufficient ductility and toughness for many structural applications that are used in temperatures above 1800° F.

Nickel-based alloy in Metal Matrix Composites (MMC) used for applications exposed to temperatures above 1800° F. are very expensive. MMCs incorporating continuous fibers reinforcement are especially expensive and slow to manufacture. Carbon fiber reinforced plastics offer excellent strength and fatigue resistance while being readily manufactural; however, such plastics are limited to temperatures below 800° F.

There is thus an urgent need to develop cost effective and readily manufactural systems with metal matrix composites that can be used in applications at significantly higher temperatures, such as above 1800° F. and up to 2200° F. Nickel-based superalloys lose their strength above 1800° F. The strength and creep resistance of this metal matrix composite appreciably increases at 2000° F. The method of manufacturing allows production of much larger composites as compared to conventional methods.

BRIEF SUMMARY OF THE INVENTION

The present disclosure is generally directed to a nickel-based alloy in a nickel metal matrix composite (Ni-MMC) and a method of manufacturing the Ni-MMC.

One embodiment of the present disclosure is directed to Ni-MMC which comprises a matrix alloy including: from about 50 to about 66 wt. % nickel; from about 10 to about 30 wt. % copper; from about 6 to about 14 wt. % chromium; and from about 5 to about 14 wt. % titanium; and at least an inner layer and an outer layer.

One aspect of the matrix in the resulting Ni-MMC in the present disclosure is its gradient nature. Particularly, in a suitable embodiment, the matrix alloy includes at least two layers; an outer layer and an inner layer. The inner layer contacts the Ni-MMC reinforcement. The inner layer is solute rich, which improves the ability of the matrix to infiltrate into the reinforcement during manufacturing. The concentration of elements in the matrix alloy which degrade gradually increases as the matrix alloy gets closer to the outer layer. Suitably the inner layer comprises nickel alloy foils, copper alloy foils, titanium alloy foils, foils containing chromium (such as nickel alloy or stainless steel). The outer layer is at the surface of the Ni-MMC is highly oxidation resistant; suitably comprising 20 to 28 wt. % chromium, more aluminum and refractory elements (such as, tungsten) than the interior layer, and may also contain rare earth metals.

The present disclosure is further directed to methods of manufacturing the resulting Ni-MMC. The method includes sequentially stacking pure metallic or commonly available alloy foils, thereby enhancing the wetting, penetration, and encapsulation of the reinforcement while controlling reaction with a reinforcement to minimize degradation of reinforcement properties. In one embodiment, the method includes: layering copper onto at least one side of a reinforcement; layering a reactive element selected from the group consisting of titanium, niobium, tantalum, hafnium, zirconium, or any combination thereof onto the copper layer; layering nickel onto the reactive element layer; layering an outer layer material onto the nickel layer; and heating all layers from about 2000° F. to about 2300° F.; wherein the method provides improved resistance of degradation of mechanical properties to the composite. Suitable outer layer materials may be Haynes 230, Nickel 601, Nickel 602, RA 333, 310 stainless steel, or any other suitable oxidation resistant material.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts an illustration of an embodiment of a reinforcement 1 layered on either side with a copper alloy 2, titanium alloy 3, nickel alloy 4, and Nickel Alloy 602 5.

FIG. 2 depicts one exemplary method of layering the elements of the disclosed nickel metal matrix composite.

FIG. 3 depicts one exemplary method of heating the layers to produce the disclosed nickel metal matrix composite.

DETAILED DESCRIPTION OF INVENTION

The present disclosure relates to a nickel-based alloy formulation in a nickel metal matrix composite (Ni-MMC). The present disclosure is also directed to a method of manufacturing the Ni-MMC. One aspect of the method involves layering economical and commonly available metallic foils (such as, copper, titanium, nickel) that are placed in a proper sequence surrounding a fiber reinforcement to create a strong and ductile metal matrix alloy.

The method of manufacturing the Ni-MMC is developed to effectively wet, infiltrate, embed, encase, support, and protect the fiber reinforcement. The disclosed Ni-MMC made with this method is intended for applications up to 2200° F., providing a significant improvement in elevated temperature properties compared to conventional nickel superalloys.

Composite

A metal matrix composite includes a metal matrix and a reinforcement. The metal matrix is a continuous metallic phase which contacts the reinforcement, in many embodiments, a fiber reinforcement.

One aspect of the matrix in the present disclosure is its gradient nature. In one embodiment, the matrix alloy includes at least two layers: an outer layer and an inner layer. The inner layer contacts the Ni-MMC reinforcement. The inner layer is solute rich, which improves the ability of the matrix to infiltrate into the reinforcement during manufacturing, which is described in detail below. The concentration of elements that are undesirable to be in contact with the reinforcement gradually increases as the matrix alloy gets closer to the outer layer.

The outer layer is the surface layer of the matrix. The chromium content of the outer layer of the resulting Ni-MMC will contain 20 to 28 wt. % chromium, more aluminum and refractory elements (such as, tungsten) as compared to the interior layer, and can also contain rare earth metals. The outer layer of the matrix is a highly oxidation and corrosion resistant up to 2200° F. Suitably, the outer layer includes one or more of Haynes 230, Nickel 601, Nickel 602, RA 333, and 310 stainless steel.

The reinforcement may be either continuous or discontinuous. The reinforcement in the present composite may include carbon fiber or ceramic fiber. A ceramic fiber may include aluminum oxide, alumina-silicates, silicon carbide, or any combination thereof. In one embodiment, the reinforcement is a continuous carbon fiber. The reinforcement may be coated with nickel or copper to enhance wetting and penetration of the fiber reinforcement during manufacturing.

The coating additionally provides mitigation of excessive reaction between the elements of the matrix and the reinforcement, which causes degradation of the resulting Ni-MMC. An example of elements that cause degradation is titanium in the inner layer of the metal matrix and a carbon fiber reinforcement. In such an embodiment, the coated reinforcement may be further coated with chromium to further increase resistance to degradation of a carbon fiber reinforcement due to the incompatibility of titanium and carbon.

One embodiment includes layering a metallic mesh on the reinforcement such that the inner layer is freely able to penetrate into the reinforcement when heated during the process, described in detail below. Suitably, the metallic mesh is nickel, cobalt, or stainless steel.

In one embodiment the Ni-MMC includes a refractory alloy mesh with percent area opening of greater than 50% to increase ductility when higher creep and toughness of the resulting Ni-MMC is needed. The refractory alloy mesh is made of one or more of tungsten, molybdenum, and niobium.

The matrix alloy, if homogenous, includes from about 50 to about 66 wt. % nickel. The composition range for nickel is selected to form an alloy with face centered cubic structure that would allow precipitation of coherent Ni3Ti and Ni3Al hardening agents via gamma prime precipitation hardening.

The matrix alloy, if homogenous, also includes from about 10 to about 30 wt. % copper. Copper is fully miscible with nickel such that it facilitates bonding among the metallic foils and the reinforcement during manufacturing, described in detail below. Copper allows increasing the titanium concentration from a maximum of 5 wt. % to a maximum of 14 wt. %. Without copper, a nickel alloy containing high levels of titanium or titanium-aluminum results in embrittlement of the matrix alloy. On the other hand, testing indicates that the matrix alloy containing less than 5% titanium cannot effectively wet and infiltrate into the reinforcement matrix.

Suitably, the matrix alloy, if homogenous, has a ratio of nickel to copper from about 2.5:1 to about 6:1. However, copper melts at a lower temperature than nickel, so it is suitable to include lower levels of copper in the Ni-MMC where the intended application temperature is above 2100° F.

The matrix alloy, if homogenous, also includes from about 6 to about 14 wt. % chromium. Chromium enhances corrosion and oxidation resistance and allows using the matrix alloy at much higher temperatures than possible without the addition of chromium.

The matrix alloy, if homogenous, also includes from about 5 to about 14 wt. % titanium; or from about 6 to about 14 wt. %. Titanium of at least 5 wt. % in the inner layer of the matrix is essential for effectively wetting and infiltrating the reinforcement without reducing the toughness of the matrix alloy. Titanium allows effective precipitation hardening; thereby enhancing room and elevated temperature strength as well as creep resistance. In one embodiment the matrix alloy includes a minimum of 6 wt. % titanium.

In some embodiments, the matrix alloy, if homogenous, may include no more than about 10 wt. % manganese. Manganese further reduces the melting temperature range of the matrix alloy allowing more effective bonding and infiltration into the reinforcement. Where manganese is present in the matrix alloy the suitable total amount of copper and manganese combined is from about 10 to about 24 wt. %.

In some embodiments, the matrix alloy, if homogenous, may include no more than about 5 wt. % aluminum. Aluminum is a strong precipitation hardening agent enhancing strength and helps the matrix alloy infiltrate and wet the reinforcement by locally suppressing the melting temperature.

In some embodiments, it is suitable for the matrix alloy, if homogenous, to have a combined concentration of titanium and aluminum between 6 and 16 wt. %.

The matrix alloy, if homogenous, may also include up to 8 wt. % iron, up to 8 wt. % cobalt, or up to 0.2 wt. % carbon for added strength.

The matrix alloy, if homogenous, may also include no more than 0.2 wt. % rare earth metals. Where rare earth metals may include one or more of: yttrium, lanthanum, gadolinium, cerium, or scandium. Rare earth metals are very reactive and form stable oxides which enhances the bonding between the matrix and the reinforcement. Additionally, rare earth metals enhance oxidation resistance of the matrix alloy, which is why they may be included in the outer layer.

In some embodiments, the matrix alloy, if homogenous, includes one or more of: no more than up to 0.6 wt. % tin; and no more than up to 5 wt. % silver. Tin and silver reduce melting temperature, which helps wetting and infiltration of the matrix alloy into the reinforcement matrix. Accordingly, it is not suitable for embodiments intended for application temperatures above 2100° F. to include tin or silver.

In one embodiment, where the matrix alloy includes both tin and titanium, the matrix alloy, if homogenous, has a ratio of titanium to tin in a ratio of at least 20:1.

In some embodiments of the matrix alloy, if homogenous, the total amount of titanium, niobium, tantalum, hafnium, and zirconium from about 6 to about 15 wt. %.

In some embodiments, the matrix alloy, if homogenous, comprises one or more of niobium or tantalum in a total amount up to 5 wt. %.

In some embodiments, the matrix alloy, if homogenous, comprises one or more of tungsten or molybdenum in a total amount up to 8 wt. %.

In some embodiments, the matrix alloy, if homogenous, comprises at least one of: up to 0.3 wt. % boron or up to 0.1 wt. % phosphorus.

Method

The present disclosure is further directed to methods of manufacturing the resulting Ni-MMC. The method includes stacking pure metal or metallic alloy foils sequentially to enhance wetting, penetration, and encapsulation of the reinforcement while controlling reaction with a reinforcement to minimize degradation of reinforcement properties.

In one embodiment, as illustrated in FIG. 2, the method includes: layering copper onto at least one side of a reinforcement 205; layering a reactive element selected from the group consisting of titanium, niobium, tantalum, hafnium, zirconium, or any combination thereof onto the pure or copper alloy layer 210; layering nickel or nickel alloy onto the reactive element layer 215; layering an outer layer material onto the nickel layer 220; and heating all layers from about 2000° F. to about 2300° F. 225; wherein the method provides improved resistance of degradation of mechanical properties to the composite. Suitable outer layer materials may be Haynes 230, Nickel 601, Nickel 602, RA 333, 310 stainless steel, or any other suitable oxidation resistant material.

One aspect of the method is to perform a metallurgical evaluation including simulation and ICME software to ensure phase compatibility, chemistry compatibility, isothermal solidification temperature, and consolidation parameters.

An additional aspect of the method of making the resulting Ni-MMC includes a reinforcement. The reinforcement may include carbon fiber or ceramic fiber. Wherein the ceramic fiber may be an aluminum oxide, alumina-silicates, or silicon carbide.

In another embodiment, the method includes coating the reinforcement with nickel or copper and possibly further coating with chromium. The reinforcement may be coated by electroplating, electroless nickel, electroless copper, chemical vapor deposition or any other coating process readily determined by those skilled in the art. In one embodiment, the carbon fiber reinforcement is coated with electroless nickel as it is self-fluxing due to the presence of boron, phosphorus, and copper. In one embodiment, the chromium coating is at least 0.0005″ thick.

One aspect of the method is arranging the metallic foils around the reinforcement judiciously to achieve a desirable melting sequence by eutectic melting or low melting temperature. Upon further diffusion into the alloy's main constituent, nickel, will result in the isothermal solidification at an engineered temperature range. This ranging also allows the metallic foils surrounding the reinforcement to fully infiltrate the reinforcement network.

One aspect of the method is the thickness of the metallic foils. The thickness of each foil should be selected such that there is an appropriate amount of each element and/or component as described herein. Examples 1 and 2 provide a detailed description of the thickness of each foil. It is suitable that the thickness of each metallic foil/layer can be reduced by as much as 60% for a Ni-MMC with higher volumetric fiber to matrix ratios.

Another embodiment of the method includes layering a metallic mesh on the reinforcement such that the inner layer is freely able to penetrate into the reinforcement when heated during the process, described in detail below. The metallic mesh further dilutes the concentration of low melting constituents to ensure isothermal solidification through diffusion at consolidation or normalization/solution treatment temperatures. Suitably the metallic mesh is nickel, cobalt, or stainless steel.

In one embodiment the Ni-MMC includes a refractory alloy mesh with percent area opening of greater than 50% to increase ductility when higher creep and toughness of the resulting Ni-MMM is needed. The refractory alloy mesh is made of one or more of tungsten, molybdenum, tantalum, and niobium. Typically, fiber reinforcement impacts performance strength at room and elevated temperatures. The addition of refractory alloy mesh provides additional reinforcement as refractory elements based alloys possess significantly higher temperature and creep resistance compared to traditional nickel-based alloys. Additionally, the refractory alloy mesh contains the matrix alloy, while simultaneously providing toughness, ductility, and damage tolerance in the resulting Ni-MMC. The use of refractory alloy mesh reinforcement improves overall toughness and ductility of the resulting Ni-MMC without reducing strength. The times and temperatures utilized for fabrication of the Ni-MMC in the disclosed method (as described more fully below) are insufficient for full dissolution of the refractory alloy mesh into the matrix alloy. However, partial diffusion among of the refractory alloy mesh allows full metallurgical bonding of the refractory alloy mesh and the matrix alloy. While a large percentage of the refractory alloy mesh retains its original chemistry and form, typically 5% to 15% of the refractory alloy mesh diameter is dissolved/diffused into the matrix alloy. The partial diffusion of the refractory alloy mesh provides additional strength, creep resistance, and toughness/ductility to the resulting Ni-MMC.

One aspect of the method is performing a metallurgical evaluation including simulation and ICME to ensure phase compatibility, chemistry compatibility, isothermal solidification temperature, and help select consolidation parameters. Additionally, the type and percentage of elements/alloys is evaluated for swelling to allow full wetting and prevent excessive reaction between the matrix and the reinforcement in the resulting Ni-MMC.

One aspect of the method is constructing, inspecting, cleaning, coating, and curing the tooling. The tooling is coated with a parting agent such as yttrium oxide, zirconium oxide, or any other ceramic coating that is suitable to one skilled in the art. The parting agent may be applied by brushing, followed by procuring at 350° F. to remove moisture and volatile organic compounds prior to assembling the foils and reinforcement.

Another aspect of the method is cleaning and curing the metallic foils and reinforcement. One embodiment includes activating the metallic foils if needed.

Another aspect of the method is stacking metallic foils around the reinforcement judiciously as to achieve desirable melting sequence.

In one embodiment, as illustrated in FIG. 1, the method involves stacking a carbon fiber reinforcement 1 layered on either side by a copper alloy foil 2, followed by a titanium alloy foil 3, followed by a nickel alloy foil 4, and followed by Nickel alloy 602 5. Example 1 provides a detailed description of a single ply Ni-MMC. It is suitable in some embodiments to repeat the layering of the foils and the reinforcement to increase the ductility of the resulting Ni-MMC. Example 2 provides a detailed description of a four ply Ni-MMC.

One aspect of the method is placing the stacked alloys in to a tooling which is then inserted in to a furnace. The tooling/furnace may have auxiliary equipment/instruments such as process control sensors, closed-loop feedback controls, tool evacuation ports, inert gas purge, compressed inert gas line, or any other sensors that are appropriate to one skilled in the art. One embodiment the furnace has a vacuum or an inert gas purge. An example of the inert gas used in the inert gas purge is argon.

The furnace heats the layers to a temperature from about 2000° F. to about 2300° F. In one embodiment, as illustrated in FIG. 3, the furnace is rapidly heated to 1800° F. and held for about an hour 310, the temperature is slowly increased to 2175° F. at a rate of about 100° F. per hour 315. Further, in such an embodiment, the temperature is held at 2175° F. for about an hour 320 before the furnace is turned off 325.

In one embodiment of the method, pressure is applied to the metallic foils and the reinforcement through differential pressure. In another embodiment, the metallic foils and reinforcement are placed inside a shaped tooling that is evacuated and welded shut/hermetically sealed and hot isostatically pressed together.

In one embodiment of the method, an execute controlled heating and consolidation program is conducted. One example of the controlled heating and consolidated program includes the tooling being closed, preliminary pressure being applied to the stack to ensure full contact between layers, a vacuum or purge gas layers, a ramp up sequence, a hold sequence, a pressurization sequence, a consolidation sequence to attain isothermal solidification followed by cooling the stack to ambient temperature.

Another aspect of the method is removing the solidified layers from the tooling. In one embodiment, after removal the solidified layers may also be solution treated and aged to further enhance mechanical properties. Examples of treatments are precipitation hardening and dispersion hardening. The solidified layers may be trimmed further and drilled, followed by final dimensional and non-destructive inspection.

When introducing elements of the present invention or the various embodiments(s) thereof, the articles “a”, “an”, “the” and “said” are intended to mean that there are one or more of the elements. The terms “comprising”, “including” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements.

In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained.

As various changes could be made in the above processes without departing from the scope of the invention, it is intended that all matter contained in the above description and shown in the accompanying drawing[s] shall be interpreted as illustrative and not in a limiting sense.

The present disclosure will be further described in the following non-limiting Examples.

EXAMPLES

Example 1—One Ply Nickel Metal Matrix Composite

In this Example, the layers of a one ply nickel metal matrix composite applied in the following order:

• • 1. A 0.01″ thick 310 stainless steel sheet;
  • 2. Two, 0.005″ thick nickel alloy foils;
  • 3. A 0.002″ copper foil;
  • 4. A 0.003″ commercially pure titanium foil;
  • 5. A 0.003″ nickel 201 foil;
  • 6. A 0.0126″ Conductive Composites 6A1-3KPW nickel coated carbon fiber cloth;
  • 7. A 0.003″ nickel 201 foil;
  • 8. A 0.003″ commercially pure titanium foil;
  • 9. A 0.002″ copper foil;
  • 10. Two, 0.005″ thick nickel alloy foils; and
  • 11. An 0.01″ thick 310 stainless steel sheet.

Example 2—Four Ply Nickel Metal Matrix Composite

In this Example, the layers of a four ply nickel metal matrix composite applied in the following order:

• • 1. A 0.01″ thick 310 stainless steel sheet;
  • 2. A 0.005″ thick nickel alloy foil;
  • 3. A 0.002″ copper foil;
  • 4. A 0.003″ commercially pure titanium foil;
  • 5. A 0.003″ nickel 201 foil;
  • 6. A 0.0126″ Conductive Composites 6A1-3KPW nickel coated carbon fiber cloth;
  • 7. A 0.003″ nickel 201 foil;
  • 8. A 0.002″ Cusiltin5 foil;
  • 9. A 0.003″ commercially pure titanium foil;
  • 10. A 0.002″ copper foil;
  • 11. A 0.005″ nickel 201 foil;
  • 12. A 0.002″ copper foil;
  • 13. A 0.003″ commercially pure titanium foil;
  • 14. A 0.003″ nickel 201 foil;
  • 15. A 0.0126″ Conductive Composites 6A1-3KPW nickel coated carbon fiber cloth;
  • 16. A 0.003″ nickel 201 foil;
  • 17. A 0.002″ Cusiltin5 foil;
  • 18. A 0.003″ commercially pure titanium foil;
  • 19. A 0.002″ copper foil;
  • 20. A 0.005″ nickel 201 foil;
  • 21. A 0.002″ copper foil;
  • 22. A 0.003″ commercially pure titanium foil;
  • 23. A 0.003″ nickel 201 foil;
  • 24. A 0.0126″ Conductive Composites 6A1-3KPW nickel coated carbon fiber cloth;
  • 25. A 0.003″ nickel 201 foil;
  • 26. A 0.002″ Cusiltin5 foil;
  • 27. A 0.003″ commercially pure titanium foil;
  • 28. A 0.002″ copper foil;
  • 29. A 0.005″ nickel 201 foil;
  • 30. A 0.002″ copper foil;
  • 31. A 0.003″ commercially pure titanium foil;
  • 32. A 0.003″ nickel 201 foil;
  • 33. A 0.0126″ Conductive Composites 6A1-3KPW nickel coated carbon fiber cloth;
  • 34. A 0.003″ nickel 201 foil;
  • 35. A 0.002″ Cusiltin5 foil;
  • 36. A 0.003″ commercially pure titanium foil;
  • 37. A 0.002″ copper foil;
  • 38. A 0.005″ nickel 201 foil;
  • 39. An 0.01″ thick 310 stainless steel sheet.

Example 3—Method of Heating

The tooling is pretreated by being brushed with a parting agent, yttrium oxide, and pre-cured at 350° F. to remove moisture and volatile organic compounds. The metallic layers, as described in Examples 1 or 2, are placed inside a tooling.

The tooling and layers are placed in a standard muffle furnace with an argon purged retort and heated to 850° F. to drive off moisture and volatile organics. The furnace was rapidly heated to 1800° F. The temperature was held at 1800° F. for an hour to achieve uniform temperature within the tooling. The furnace temperature was slowly increased at a rate of about 100° F. per hour until the furnace reached the temperature of 2175° F. The temperature was held at 2175° F. for about an hour under an argon purge. Then the furnace was turned off. The argon purge continued until temperature had dropped below 1500° F.