KR20010031873A - Method for producing a sacrificial body for producing aluminal titanium aluminide composite bodies - Google Patents

Abstract

The present invention relates to a process for preparing a saccharide for the preparation of a component with an Al ₂ O ₃ / titanium aluminide composite in a starting mixture, to a starting mixture and to a sacrifice. A molded body is formed by compressing the starting mixture to which titanium, carbon or carbon precursor, filler and binder are added as oxides. At the conversion temperature, the shaped body undergoes heat treatment to form a pressure-stable sacrificial body. In this process, the filler and the binder are removed, but the sacrificial body is filled with aluminum or an aluminum alloy under pressure, and the filling is performed at a filling temperature higher than the conversion temperature. A solid state reaction occurs between the material of the filled sacrificial material and aluminum, ₂ O ₃ / titanium aluminide complex is formed.

Description

FIELD OF THE INVENTION [0001] The present invention relates to a method for manufacturing a sacrificial body for alumina titanium alumina composite,

DE 196 05 858 A1 discloses a process for making components from Al ₂ O ₃ / titanium aluminide composites. Ceramic / metal composite materials have high strength and high fracture toughness because they combine the properties of ceramics and metals. In the process of forming the basis of the pre-feature section, a starting mixture is formed containing oxides which can be reduced by means of aluminum in order to simultaneously form aluminide and Al ₂ O ₃ . The constituents of the starting mixture is TiO _2. A sacrifice close to the final form is prepared from the starting mixture and then Al is infiltrated. The sacrificial body is stabilized and sintered under pressure prior to penetration for aluminum filling. The temperature of the sacrificial body after sintering is the filling temperature at which the aluminum and the aluminum alloy (hereinafter referred to as aluminum) are above the melting temperature. Moreover, the fill temperature is below the reaction temperature at which the so-called SHS reaction takes place between aluminum and at least one component of the starting material. The SHS reaction (self-propagating high-temperature synthesis reaction) takes place very quickly above the reaction temperature and is highly pyrogenic and almost uncontrollable. Under pressure at the filling temperature, the sacrificial body is filled with aluminum and reheated, after which an exchange reaction takes place between aluminum and the sacrificial component to form an Al ₂ O ₃ / titanium aluminide composite.

However, the sacrifice is converted to Al ₂ O ₃ / titanium aluminide composites only in certain regions. In addition, the sacrifice containing TiO ₂ in DE 196 05 858 A1 is completely filled with aluminum only in certain cases. In addition, the continuous titanium aluminide phase is provided only in exceptional cases to the sacrifice having this property.

DE-P 19710671.4 discloses a method for producing a component from a metal / ceramic composite wherein the sacrificial body comprising the ceramic precursor is filled with a thermally softened metal, in particular aluminum or a metal alloy. The filling temperature is less than the reaction temperature and the exchange reaction occurs between the metal of the ceramic precursor and the metal of the filling metal at the reaction temperature. After the sacrificial body is as completely filled as possible, the filled sacrificial body is heated above the conversion temperature and the exchange reaction just mentioned occurs. This exchange reaction produces components made of metal / ceramic composites including ceramic phases and metal phases with intermetallic bonds between the metal of the ceramic and the metal of the fill metal. By heating below the reaction temperature at which the exchange reaction occurs between the fill metal and the sacrificial material, the softened metal is filled into the sacrificial body, thereby maintaining the ceramic matrix during the subsequent exchange reaction between the filler and the introduced metal and the sacrificial material. The pores of the sacrificial body are completely filled so that when the material in question is used in stoichiometric amounts, all of the ingredients are fully reacted and there is no cracks or channels. Particularly, since the fill metal is aluminum and the metal of the ceramic is titanium, the ceramic phase includes TiB _x or TiC _y or TiCN and Al ₂ O ₃ after the exchange reaction, and the intermetallic compound on the metal is high heat-resistant titanium aluminide, especially TiAl. The properties of such a metal / ceramic composite material are good. Therefore, the metal / ceramic composite material prepared using aluminum as the filler metal and Ti as the metal of the ceramic sacrificial body has a density of 3.4 g / cm 3. This density is slightly higher than the density of the MMC (metal-ceramic composite) but is 42% of the cast iron density. In embodiments where the high heat resistant compound is present in the form of an intermetallic compound TiAl, the range of use of the component is at least 800 DEG C, which is much higher than that of gray cast iron. The fabricated metal / ceramic composites are used in the manufacture of disc brake friction response friction rings. Such a friction ring is fixed to the hub of the brake disc by means such as a screw.

However, before the sacrificial body is filled with the metal or the alloy, the starting material of the sacrificial body must be heated and exchange reaction between the precursors should occur to form an advanced precursor. After the metal filling, the ceramic phase and the metal phase are formed from the precursor and the metal, and the exchange reaction is again used between the precursor and the filler metal to form an image.

US-A-4,988,645 discloses a process for impregnating ceramic sacrificial bodies with aluminum. In this process, a ceramic body is produced using an SHS reaction (a self-propagating high-temperature synthesis reaction in which the reaction mixture itself reacts to provide a ceramic matrix as a reaction product).

However, the components produced in this way have an unacceptable level of porosity and thus have a high percentage of rejects. In particular, the filling of the sacrificial body containing TiO ₂ as a precursor of the sacrificial body is very poor.

WO 84/02927 discloses a process for manufacturing fiber-reinforced die-cast parts containing aluminum using a so-called squeeze-cast process. In this process, the porous initial body of fiber-containing starting mixture is compressed and filled with aluminum. A binder is added to the starting mixture to stabilize the porous initial body and to maintain the orientation of the fibers arranged in the initial body and removed by heat during the filling of the initial body. Due to the presence of pores and the strength of the binder, the initial body undergoes no deformation or is negligibly deformed. In this case, there is no chemical reaction between the filled aluminum and the starting material of the initial body, so the effect of this reaction on the structure and form of the diecast component is unknown.

All of the above methods require high energy due to various heat treatments such as sintering at a temperature higher than the filling temperature, the first exchange reaction, the filling and the subsequent second exchange reaction. Therefore, the process cost is high.

The present invention relates to a process for the preparation of a sacrificial body for the production of a composition consisting of an Al ₂ O ₃ / titanium aluminide composite according to the preamble of claim 1, a starting mixture for preparing a sacrificial product according to the preamble of claim 16, , Which are known from DE 196 05 858 A1.

It is an object of the present invention to improve the known processes so that the manufacture of the components from the metal / ceramic composites is simpler, faster, cheaper, more energy efficient and the titanium aluminide is provided as reliably as possible to the composite.

This object is achieved by the features of claim 1 using a sacrificial body on which the present invention is based. Molten Al is simultaneously infiltrated by using a stable sacrificial body containing reduced titanium oxide TiO _x (x = 1, 1.5, 1.67) or TiO ₂ reduced by carbon and formed and machined close to the final shape Can be infiltrated by pressure very well.

Two known exchange reactions, which convert aluminum and sacrificial material into an Al ₂ O ₃ / titanium aluminide composite formed from the starting material, can be performed in a single heating process.

The conversion temperature is below the fill temperature, especially below the aluminum melting temperature, and even below 400 ° C. The required energy consumption and manufacturing time are shortened.

The sacrificial body is heated to fill the sacrificial body with aluminum or an aluminum alloy. It is preferable to use TiO ₂ and C for the preparation of the sacrificial material since the reduced titanium oxide TiO _x (TiO ₂ , Ti ₂ O ₃ , or Ti ₃ O ₅ ) under certain circumstances can be formed from TiO ₂ and C when heated .

Surprisingly, however, there is no exchange reaction to form the Al ₂ O ₃ / titanium aluminide composite while permeating the sacrificial body under pressure with aluminum. Al ₂ O ₃ / titanium aluminide composites are formed solely through solid-state reactions and their process temperatures are below the melting temperature of aluminum.

Carbon and TiO ₂ with a garuhyeong ceramic starting mixture contains a binder and filler are mixed and compacted at a later time.

The filler and the binder are fired under vacuum or protective gas by means of a low temperature heat treatment at 350 to 700 ° C, especially 400 ° C under vacuum or nitrogen or CO ₂ protective gas to form a sintered porous pressure-stable ceramic sacrificial body.

At the same time, thermogravimetric analysis (TG) is performed to confirm that the binder and filler are completely removed.

Due to the controlled addition of fillers and binders, precisely defined porosity, pore structure and strength can be obtained, allowing pressure infiltration of the sacrificial body using aluminum.

One of the advantages of the present invention is that during the entire period of manufacturing the component from the metal / ceramic composite material, that is, from the preparation of the sacrificial body to the formation of the composite material by the filling and exchange reaction of the aluminum- Especially at temperatures above 700 ° C. On the other hand, filling by pressure casting takes place within a short time.

In addition, aluminum is converted to high heat-resistant titanium aluminide. In addition, very cheap raw materials are used. The raw material cost is 4 DM per kg.

Titanium dioxide and graphite are mixed in a defined stoichiometric ratio relative to each other to produce a starting mixture. Thereafter, a binder aqueous solution such as 1-3% by weight of polyvinyl alcohol (PVA) or polyethylene glycol (PEG) is added to the homogeneous mixture and kneaded. After binder addition, a water soluble organic filler in powder or fiber form, especially a cellulose derivative such as cellulose acetate, is added to the mixture and kneaded.

The filler added in powder form has an average size of 10 to 100 mu m, especially 20 mu m. The mixture is allowed to stand in a dry or moist state (moisture remaining 10-20% / H ₂ 0) is uniaxial compression at 300 bar. After the uniaxial compression process, the cold isostatic pressing process is performed.

The sacrificial body compressed to a final shape is machined to final dimensions and introduced into a die-casting die, and the sacrificial body is filled with liquid aluminum.

The strength, elastic modulus, porosity and pore structure of the sacrificial body are important in the aluminum filling in the die-casting process.

These properties are influenced by the choice of filler and binder, the amount of filler and the compression pressure. In addition, the particle size of the ceramic powder (TiO _2, etc.) and the particle size of the filler are also affected.

The relationship between the affecting and target parameters is presented in Table 1.

Effects of Process Variables on the Properties of Sacrifices Goal parameters Affecting Parameters Type of filler Amount of filler Compressive pressure Particle size Initial Strength Modulus Porous Pore Structure + + +++ ++ + +++ ++ ++ ++ ++++ +++ +++

+ = Has some effect; ++ = moderate impact; +++ = very large impact

A starting mixture for sacrificial body formation is presented.

Example 1

3 mol TiO ₂ (average particle diameter d ₅₀ = 0.3 μm) is mixed with 1 mol of C (d ₅₀ = 0.05 μm) in a kneader (manufactured by Eirich) for 10 minutes. 3 wt% polyethylene glycol (20% aqueous solution) is added to the mixture and kneaded. 10 wt% cellulose acetate (CA) (d ₅₀ = 20 탆) is then added to the moist mixture and mixed in a kneader. The powder is uniaxially compacted at 30 MPa. After that, cold isostatic compression is performed at 200 MPa. When the sacrificial body is heated at 700 DEG C for 1 hour under nitrogen (maintained at 350 DEG C and the heating rate is 1 K / min), all the organic additives are burned to leave no residue. This sacrificial body has a compressive strength of 7 MPa and a porosity of 49%. The pore diameter has a bimodal distribution with a maximum at 0.1 탆 and 20 탆.

Example 2

Except that the molar ratio of TiO ₂ and C was 3/2. In this case, additional iso-compression is required at 300 MPa.

Example 3

And the amount of cellulose acetate was 20% by weight.

Example 4

The same as Example 1 except that 10 wt% of water was added to the TiO ₂ / C / PEG / CA mixture before uniaxial compression.

Example 5

The same as Example 1 except that 1 wt% of water was added to the TiO ₂ / C / PEG / CA mixture before uniaxial compression.

Example 6

A short constontane wire or C fiber was added to the TiO ₂ / C / PEG / CA mixture. This increases fracture elongation.

Example 7

The TiO ₂ particle size is the same as in Example 1 except that it has a diameter of 15 mu m on average. The compressive strength increases to 7.5 MPa.

The sacrificial body is pressurized and filled with aluminum. After filling, the sacrificial body is subjected to heat treatment at a temperature lower than the melting point of aluminum to form a composite material including TiC, Al ₂ O ₃ and Al ₃ Ti uniformly distributed.

A solid state reaction takes place during the subsequent heat treatment to produce a composite material. Therefore, this reaction takes place below the melting point of aluminum. These homogeneous composite materials have high heat resistance and wear resistance.

The manufacturing method, starting mixture or sacrificial body according to the invention is particularly suitable for the production of friction surfaces of friction systems, engine components, vehicle components or brake discs. The friction system means the structural components of the jet engine and motor as well as the brake disc, in particular the sliding contact bearing and the cutting material.

Claims (40)

Titanium as an oxide is added to the starting mixture, the starting mixture is compressed to form a compact, the compact is heat-treated at the conversion temperature to form a sacrificial body, and the sacrificial body is filled with aluminum or an aluminum alloy under pressure, the Al ₂ O ₃ / titanium aluminide from a starting mixture consisting of forming a composite according to the method of producing the Al ₂ O ₃ / titanium aluminide composites for preparing the sacrificial material, carbon or a carbon precursor, filler and binder is the starting mixture And the starting mixture is compressed to form a shaped body and each component of the starting mixture is bound together by a binder in a pressure-stabilized manner and the decomposition temperature of the filler and the binder is selected to be below the fill temperature, While filling the sieve with aluminum or Wherein the filler and the binder are previously removed and the conversion temperature is set below the fill temperature so that the formed body is converted to the sacrifice during heating to the fill temperature for subsequent pressurization. The method of claim 1, wherein the compressed sintered sacrificial body is filled with aluminum. The method according to claim 1, wherein the sacrificial material is produced close to the final shape. 2. A method according to claim 1, wherein the sacrificial body is compressed and subsequently machined close to the final shape. The method according to claim 1, wherein the titanium oxide used is TiO, Ti ₂ O ₃ , Ti ₃ O ₅ or TiO ₂ . The method of claim 1, wherein the titanium oxide used is TiO ₂ , TiO ₂ is reduced by the carbon, and the reducing carbon is formed during the thermal removal of the filler and the binder and remains in the sacrificial material. The process according to claim 1, wherein the filler is evaporated below the fill temperature or bound to the carbon. The method of claim 1, wherein the binder is evaporated below the fill temperature or converted to carbon. The method according to claim 1, wherein the filler is a thermoplastic or thermosetting organic material selected from starch, wheat flour or a cellulose derivative such as cellulose acetate. 2. A process according to claim 1, characterized in that the starting material of the starting mixture is homogeneously dispersed. The process according to claim 1, wherein 1-3% by weight of the binder is added to the starting mixture. The method according to claim 1, wherein the selected binder is an aqueous solution of polyvinyl alcohol (PVA) or polyethylene glycol (PEG). The method according to claim 1, wherein the selected filler is a powder having a particle size of 10 to 100 μm, especially 20 μm. The process according to claim 1, wherein the nonvolatile additives TiC, SiC, BaC or TiB ₂ are added to the starting mixture at the charging temperature. The process according to claim 1, wherein inorganic or ceramic fibers are added to the starting mixture. The starting mixture including titanium as an oxide is compressed shaped body being formed receives a heat treatment in a molded article is conversion temperature and the formed body is sacrificed during the filling temperature be aluminum or an aluminum alloy filled into the sacrificial material with the material and the aluminum of the sacrificial body reaction Al ₂ O ₃ / titanium aluminide composite to form an Al ₂ O ₃ / titanium aluminide composite from the starting mixture and to prepare a starting mixture for sacrificial preparation, wherein the carbon or carbon precursor, the filler and the binder are the starting mixture And the starting mixture is compressed to form a shaped body and each component of the starting mixture is bound together by a binder in a pressure-stabilized manner and the decomposition temperature of the filler and binder is selected to be below the fill temperature, While the unfilled sacrificial body is filled with aluminum, Before the filler and the binder is removed, and the sacrificial material for preparing the starting mixture to a shaped article characterized in that the switched body sacrificed during the transition temperature is set to be less than filled with a filling temperature heating temperature. 17. The method of claim 16 wherein the titanium oxide _{TiO, Ti 2 O 3, Ti} 3 O 5 , or the starting mixture, characterized in that the carbon and reaction of the TiO ₂ used a reducing action. 17. The method of claim 16 wherein the titanium oxide is TiO ₂ and the starting mixture, characterized in that the carbon is formed a reducing activity while TiO ₂ is reduced by the carbon filler and thermal removal of the binder used. 17. The method of claim 16, wherein the filler and the binder are evaporated below the fill temperature or converted to carbon. The starting mixture according to claim 16, characterized in that the filler is a thermoplastic or thermosetting organic material selected from starches, wheat flour or cellulose derivatives such as cellulose acetate. 17. A starting mixture according to claim 16, characterized in that the starting material of the starting mixture is homogeneously dispersed prior to compression for sacrificial formation. 17. A starting mixture according to claim 16, characterized in that the starting mixture comprises from 1 to 3% by weight of binder. The starting mixture according to claim 16, wherein the binder is an aqueous solution of polyvinyl alcohol (PVA) or polyethylene glycol (PEG). The starting mixture according to claim 16, characterized in that the filler is a powder having a particle size of from 10 to 100 μm, in particular 20 μm. The method of claim 16, wherein the starting mixture, characterized in that the starting mixture comprises a non-volatile additives, TiC, SiC, BaC or TiB ₂ in the sacrificial material filling temperature. 17. A starting mixture according to claim 16 wherein inorganic or ceramic fibers are included in the starting mixture. The sacrificial body contains titanium as an oxide and the starting mixture is compressed, and the formed body is subjected to heat treatment at the transition temperature to form a sacrificial body, and the sacrificial body is filled with aluminum or an aluminum alloy so that the sacrificial body and aluminum react with each other to form Al ₂ O ₃ / In a sacrificial body for preparing a component made of an Al ₂ O ₃ / titanium aluminide composite which produces a component made of a titanium aluminide composite, a carbon or carbon precursor, a filler and a binder are added to the starting mixture and the starting mixture is compressed The molded body is formed and each component of the starting mixture is bonded to each other in a pressure-stabilized manner by a binder, and the decomposition temperature of the filler and the binder is selected to be below the fill temperature to compress the starting material to fill the unfired sacrificial body formed with aluminum During or before the filler and binder are removed and the conversion on The Al ₂ O ₃ / Ti alumina sacrificial member id in the composite material for preparing component, characterized in that the filling temperature is less than. The method of claim 27, wherein the titanium oxide is a sacrificial member, characterized in that the _{TiO, Ti 2 O 3, Ti} 3 O 5 or TiO _2. The method of claim 27, wherein the titanium oxide is a sacrificial member, characterized in that the carbon is formed during the reduction action TiO ₂ and TiO ₂ is reduced by the carbon filler and thermal removal of the binder. 28. The sacrificial compound of claim 27, wherein the filler and the binder are vaporized below the fill temperature or bound to the carbon. 28. The sacrificial product of claim 27, wherein the filler is a thermoplastic or thermoset organic material selected from starch, flour or a cellulose derivative such as cellulose acetate. 28. The sacrificial composition of claim 27, wherein the starting material is uniformly dispersed in the sacrificial material. 28. The sacrificial composition of claim 27, wherein 1-3% by weight of the binder is included in the sacrificial material. 28. The sacrificial product of claim 27, wherein the binder is an aqueous solution of polyvinyl alcohol (PVA) or polyethylene glycol (PEG). A sacrificial body according to claim 27, wherein the filler is a powder having a particle size of 10 to 100 탆, particularly 20 탆. 28. The method of claim 27, the filling temperature is non-volatile additives, TiC, SiC, TiB ₂ BaC or sacrificial material, characterized by contained in a sacrificial material. 28. A sacrificial body according to claim 27, wherein the inorganic or ceramic fiber is contained in the sacrificial body. A manufacturing method according to claim 1 for manufacturing a friction surface of a friction system, an engine component, a vehicle component, or a brake disk. A starting mixture according to claim 16 for the preparation of a friction system, an engine component, a vehicle component, or a friction disc of a brake disc. A friction body, an engine component, a vehicle component, or a sacrificial body of claim 27 for manufacturing a friction surface of a brake disk.