EP1943039B1 - Method for producing a wear-resistant aluminum alloy, an aluminum alloy obtained according to the method, and use thereof - Google Patents

Abstract

The invention relates to a method for producing a wear-resistant aluminum alloy, to an aluminum alloy produced according to the method, and to the use thereof. The method comprises the steps of: (i) providing an aluminum alloy having the composition Fe: 3-10; X: 3-10; Y: 0-1.5; Z: 0-10; wherein X represents an element or combination of elements (a) V and Si; (b) Cr and Ti; (c) Ce; or (d) Mn; each time with the proviso that the proportion of the individual elements in the combinations of elements (a) and (b) is at least 0.5 wt %; Y represents one or more grain-refining elements selected from the group of B, Ce, Sr, Sc, Mg, Nb, Mn and Zr, unless already present as X; Z represents one or more additives increasing the heat resistance, selected from the group of ceramic fibers, particles and platelets, the figures referring to % by weight in the alloy, and Al and production-related impurities representing the remaining proportion in the alloy to make 100 wt %, with the proviso that the proportion of Al in the alloy is at least 80 wt %; (ii) melting the aluminum alloy, dissolving and homogenizing the alloy elements at temperatures of from 650° C. to 1,000° C.; and (iii) casting the melt into a casting mold at a casting temperature ranging from the melting temperature of the alloy up to a temperature 150° C. above the melting temperature.

Description

Technical area

The invention relates to a new use of a wear-resistant aluminum alloy.

Background of the invention and prior art

Motorized bearings with sliding elements made from an aluminum base alloy are found, for example, in a piston-piston-ring-cylinder-track assembly or crankshaft-bearing shell assembly, particularly in the form of crankshaft bearing shells, cylinder liners, piston rings, pistons and valve guides.

The sliding surfaces of the sliding elements can also be coated or treated thermochemically. Since the thirties of the last century, cylinder liners made of eutectic AlSi alloys ("silumin") with coarse Si primary crystals have been known and used in motor applications. These may contain up to 1.3% by weight of iron. The material matrix of these concepts is based on aluminum and silicon. For the functional design of the cylinder surface, it is essential to reset the aluminum matrix by 0.5 - 2 μm by chemical or mechanical treatments of the raceways, so that the hard silicon crystals (Hv ~ 12 - 14 GPa) form the supporting component.

The lowest system wear (piston ring and cylinder bore) is achieved by AlSi raceways against nitrided piston rings, which may be the same or in some cases better than the wear expectation of high-carbon cast iron cylinder liners (3.3 - 3.8 wt.% C). The patent US 6,030,577 discloses AlSi (17-35 wt% Si) with 3-5 wt% Fe.

Overall, however, it has been shown that this proven pairing of AlSi alloys no longer tribologically resists the loads of new or future highly-charged and / or hydrogen-powered engines. It turns out that this applies to AlSi17 (Alusil) as well as AlSi25 alloys ("SILITEC"). Furthermore, the AlSi alloys are limited in the tribological good load or feeding load with regard to the tribological high-pressure properties.

1. a. Al-Mg₂Si-Mg mit einer Schmelztemperatur von 555°C,
2. b. Al-Mg₂Si-Al₃Mg₂ mit einer Schmelztemperatur von 451 °C oder
3. c. Al_30,9Mg_69,1 ⇔ Mg + Mg₁₇Al₁₂ + Mg₂Si mit einer Schmelztemperatur von 437°C.

The very readily castable material system Al-Si-Mg, eg Al-9.0Si-0.5Mg (A359), is characterized by a strongly decreasing strength with the temperature and by the following eutectic equilibria with low temperature:

1. a. Al-Mg ₂ Si-Mg having a melting temperature of 555 ° C,
2. b. Al-Mg ₂ Si-Al ₃ Mg ₂ with a melting temperature of 451 ° C or
3. c. Al _30.9 Mg _69.1 ⇔ Mg + Mg ₁₇ Al ₁₂ + Mg ₂ Si with a melting temperature of 437 ° C.

Similar phase equilibria also exist in the material system Al-Cu-Zn.

The hot strength of AlSi alloys can be improved by ceramic fibers, particles and / or platelets, such as AlSiMg 30% by volume SiCp (Lanxide Corp., Al-7.0Si-0.3Mg) or A359-20% by volume. SiCp (p = platelet) or reinforced by particles of silicon carbide, such as DURALCAN F3S.20S, 20 wt .-% SiC) or AA6061 + 40 vol .-% Al ₂ O ₃ (Al-1% Mg + 30 wt .-% Al ₂ O ₃ (PRIMEX ™). However, piston ring wear is negatively affected by the ceramic phases.

For optimum combustion of H ₂ -driven engines, the high thermal diffusivity of aluminum (K ^RT ~ 60-80 mm ² / s) is essential, resulting in cylinder liner coatings with engineering ceramics, cermets or hard metals despite proven, better wear resistance , exclude. For comparison: K ^RT = 16.6 mm ² / s of a lamellar gray cast iron with 3.7% by weight C.

The patent US 4,948,558 discloses a fabric system AlFeXY. In addition to the intermetallic phases, amorphous and crystalline aluminum phases characterize the microstructure morphology of the rapidly solidified Al special alloys. So far, these heat-resistant special alloys, eg. B. Al88.5 Fe8.5 V1.3 Si1.7 or Al84.5Fe7Cr6Ti2,5, technologically complex rapidly melted by melt atomization and then compacted and extruded or represented powder metallurgy. The alloys have hitherto not been mentioned in connection with wear-stressed components or with "classical" casting under the influence of gravity or pressure in molds or molds.

The patent US 5,318,641 ALCOA discloses in the Al-Fe-Ce material system the alloy (X8019) with a tensile strength at RT of up to 1,600 MPa with crystalline nanoparticles precipitated in a partially amorphous matrix. The amorphous or partially amorphous microstructure recrystallizes above 300-450 ° C (Al90.8 Fe6.2 Nb1.0 Si2.0 (at.%), At 450 ° C), thus losing the high strengths. This goes hand in hand a grain coarsening. By powder atomization, melt spinning or spray compacting with subsequent compacting and / or extrusion, no cylinder liners or engine blocks can be economically produced in a large series, especially in comparison to competitive solutions, such as thermal spraying or laser nitriding of gray cast iron.

All ultra-high-strength Al special alloys with 800 MPa <σ _Tensile ^RT <1.600 MPa are produced either by powder metallurgy or by powder atomization or by melt spinning or spray compacting. They have a high volume fraction of intermetallic phases, which are present as fine dispersoids smaller than 50-100 nm due to the rapid solidification.

The patent application US 2003/0185701 (KL Sahoo et al. ) discloses casting parameters for the Al-Fe-V-Si material system. Thereafter, the casting temperatures are 800-1,000 ° C, being poured in a preheated to 350-500 ° C mold. The inoculum for grain refining consists of <1.0 wt.% Mg / Ni. A reference to tribologically stressed surfaces is neither refilled nor disclosed, nor the casting temperatures of the invention.

The publication of Sahoo et al., J. of. Materials Processing Technology 135 (2003) 253-257 , for an Al-8.3 Fe-0.8V-0.9Si alloy, presented the mechanical properties and grain morphologies grain-fined with 0.18 wt% Mg, which solidified at 1 K / s to 14 K / s.

The after US 2003/0185701 Al-8.3 Fe-0.8V-0.9Si alloys prepared with and without grain refining by 0.1-1.0% by weight Mg Vickers hardnesses of between 43-143, which are significantly lower than those of the alloys of the present invention.

The Chinese publication of Z.-H. Chen et al., J. Cent. South Univ. Technol. Vol. 7, no. 4, Dec. 2000 , represents the manufacture of components from an AA8009 alloy according to the OSPREY process. A reference to tribologically stressed surfaces is neither refilled nor disclosed.

The patent application US 2004/0156739 discloses for turbine applications aluminum alloys with up to 20 wt% rare earths cast at cooling rates of 10-100 K / s. A reference to tribologically stressed surfaces is neither refilled nor disclosed.

The patent application US 2004/0261916 discloses the dispersion-strengthening material system Al-Ni-Mn, wherein the alloys consisting of 0.5-6.0 wt .-% Ni and 1.0-3.0 wt .-% Mn with up to 0.3 wt .-% Zr and / or Sc can be grainfilled. A reference to tribologically stressed surfaces is neither refilled nor disclosed.

The patent application US 2004/0140019 For example, the dispersion strengthening system discloses Al + <11 wt.% (Mg, Li, Si, Ti, Zr) which is enriched by cryogenic milling with up to 0.3 wt.% nitrogen. This will be pipes in US 2004/0255460 manufactured for the management of cryogenic media. Reference to casting technologies or tribologically stressed surfaces is neither refilled nor disclosed. Sahoo, et al., Materials Science and Engineering, 2003, A355, pp. 193-200 , describe the formation of intermetallic phases in Al / Fe / V / Si alloy systems.

FR 2 880 086 A1 describes the use of a wear-resistant aluminum alloy in brake discs and brake drums.

There is therefore a continuing need for a material that overcomes the described limitations of the prior art.

Summary of the invention

1. (i) Bereitstellen einer Aluminiumlegierung der Zusammensetzung
   • Fe: 3 - 10;
   • X: 3 - 10;
   • Y: 0 - 1,5;
   • Z: 0 - 10;
   worin
   X für ein Element oder eine Elementkombination
   1. (a) V und Si;
   2. (b) Cr und Ti;
   3. (c) Ce; oder
   4. (d) Mn
   steht, jeweils mit der Maßgabe, dass der Anteil der einzelnen Elemente in den Elementkombinationen (a) und (b) mindestens 0,5 Gew.-% beträgt; Y für ein oder mehrere Kornfeinungselemente ausgewählt aus der Gruppe B, Ce, Sr, Sc, Mg, Nb, Mn und Zr steht, sofern diese nicht bereits als X vorhanden sind; Z für einen oder mehrere eine Warmfestigkeit erhöhende keramische Zusätze ausgewählt aus der Gruppe Fasern, Partikel und Platelets steht; und wobei sich die Angaben auf Gew.-% an der Legierung beziehen und Al sowie herstellungsbedingte Verunreinigungen den auf 100 Gew.-% verbleibenden Restanteil an der Legierung einnehmen, mit der Maßgabe, dass der Anteil von Al an der Legierung mindestens 80 Gew.-% beträgt;
2. (ii) Schmelzen der Aluminiumlegierung, Auflösen und Homogenisieren der Legierungselemente bei Temperaturen von 650°C bis 1.000°C; und
3. (iii) Gießen der Schmelze in eine Gussform bei einer Gießtemperatur, die in einem Bereich beginnend mit einer Schmelztemperatur der Legierung bis zu einer Temperatur von 150°C oberhalb der Schmelztemperatur liegt.

The invention relates to the use of a wear-resistant aluminum alloy for the production of sliding elements in crankshaft bearing shells, cylinder liners, piston rings, pistons, valve guides, bearing bushes or bearing shells. The aluminum alloy is made by a process comprising the steps of:

1. (i) providing an aluminum alloy of the composition
   • Fe: 3 - 10;
   • X: 3 - 10;
   • Y: 0-1.5;
   • Z: 0-10;
   wherein
   X for an element or an element combination
   1. (a) V and Si;
   2. (b) Cr and Ti;
   3. (c) Ce; or
   4. (d) Mn
   in each case with the proviso that the proportion of the individual elements in the element combinations (a) and (b) is at least 0.5 wt .-%; Y is one or more grain refining elements selected from the group B, Ce, Sr, Sc, Mg, Nb, Mn and Zr, if these are not already present as X; Z is one or more high-strength ceramic additives selected from the group consisting of fibers, particles and platelets; and wherein the indications relate to wt .-% of the alloy and Al and production-related impurities occupy the remaining amount of 100 wt .-% of the alloy, with the proviso that the proportion of Al in the alloy at least 80 wt. % is;
2. (ii) melting the aluminum alloy, dissolving and homogenizing the alloying elements at temperatures of 650 ° C to 1000 ° C; and
3. (iii) casting the melt into a mold at a casting temperature which is in a range from a melting temperature of the alloy to a temperature of 150 ° C above the melting temperature.

Wear resistance, tribological carrying capacity and heat resistance of the aluminum base alloys are improved. This may be due to intermetallic phases precipitated in the microstructure, such as AlFe ₃ , Al ₃ Fe (Hv - 9.8 GPa, Θ), Al ₅ Fe ₂ (η, H _v ~ 10.5 GPa), Al ₆ Fe, Al ₁₃ Fe ₄ , Al ₅ Fe ₂ (η, H _v ~ 10.5 GPa), Al ₃ (Ti, Cr), Al ₃ Ti, Al ₄ (Cr, Fe), Al ₁₀ (Cr, Fe), AlSi ₂ or Al ₈ Fe ₂ Si, which have microhardnesses of 4,000-8,000 MPa.

In the metallurgy according to the invention, no eutectic melt equilibria with liquidus temperatures below 600-620 ° C. are formed. Preferably, therefore, the silicon content should not exceed 2.0 wt%, more preferably not exceed 1.0 wt% Si. The intermetallic phases are formed from eutectic (α-Al ⇔ Al ₃ Fe) and peritectic phase equilibria.

The alloys used according to the invention differ morphologically, above all in the embodiment of the dendrites from intermetallic phases, from the silicon crystals precipitated in known AlSi alloys. The silicon crystals are present in aluminum alloys as individual single crystals, while a dendritic network allows an excellent integration into the matrix for absorption for shear stresses from the tribological stress. The alloys according to the invention can be clearly characterized by their production process.

The solid state in the aluminum, or hardly soluble alloying elements, such as. Fe, Ti, Cr, Mo or V, can be represented by means of simple casting technology as a homogeneous, segregation-free structure. This is achieved in particular by the grain refining with an element selected from the group B, Ce, Sr, Sc, Mg, Nb, Mn and Zr and by special casting temperatures.

It should be noted that a prediction of the formation of intermetallic phases or dendrites during casting is not possible, but their presence significantly influences the tribological material properties. The lack of predictability of intermetallic phases, morphology and composition of the individual components of the microstructure as well as the problems arising from eutectic phase formation make purely theoretical considerations for the prognosis of suitable materials unsuitable. It has been proven experimentally that by maintaining the temperature of the melt at more than 650 ° C, a phase equilibrium over the entire volume of the material in a useful period for commercial application sets.

After melting and homogenizing, between 0.5% by weight and 0.8% by weight of one or more of the elements selected from among boron, Ce, Sr, Sc, Mg, Nb, Mn or Zr may be used for grain refinement be alloyed. Grain refinement primarily reduces the size of the dendrites of the intermetallic phases precipitated on solidification, but also leads to an increase in the number of nuclei / density during the primary crystallization of the aluminum.

A higher cooling rate of> 100 K / s achieves the same effect, so that the grain refining is advantageously to be used for larger wall thicknesses of the castings in order to obtain a uniform microstructure. The still relatively large dendrites are favorable for a tribological sliding stress and for the connection of the intermetallic phases in the structure, but not for the Nachalimentierung the solidification front with melt. Therefore, an optimum in size must be sought in each case by grain refining elements optionally with the aid of magnetic stirring.

The formation of the dendrites from the intermetallic phases can also be prevented by magnetic stirring. The magnetic stirring also improves the alimentation of the solidification front with fresh melt, thus helping to avoid voids.

Preferably, the casting temperature in step (iii) is in the range of 1 ° C to 80 ° C, in particular in the range of 10 ° C to 50 ° C, above the melting temperature of the alloy. The casting temperatures are preferably below 800 ° C.

According to a further preferred variant of the method, an alloy with 4-8 wt .-% of Fe and / or 3-5 wt .-% of X is provided. Furthermore, it is preferred that X for the element combination (a) is specified such that a proportion of Si is less than or equal to 2 wt .-%, in particular less than or equal to 1 wt .-%. The measures mentioned lead to aluminum alloys, with particularly favorable tribological behavior.

Preferably, steps (ii) and (iii) are part of a metallurgical melt casting process selected from the group of sand casting, die casting, continuous casting, strip casting, centrifugal casting and cold crucible casting. The methods mentioned can be implemented particularly simply in conjunction with the method used according to the invention. The existing alloy workpiece can preferably be processed by drop forging. The workpiece is completely surrounded by the closed tool, the die, and the introduced into the die engraving determines the shape of the finished molding.

Finally, it is preferred if the temperature of the mold is in the range of 450 ° C to 600 ° C. As a result, aluminum alloys can be produced with particularly favorable tribological behavior.

The invention further relates to crankshaft bearing shells, cylinder liners, piston rings, pistons, valve guides, bearing bushes or bearing shells with a sliding element of the aforementioned aluminum alloy.

Fig. 1 bis 3

Probenquerschnitte durch AlFeVSi-Legierungen;

Fig. 4 und 5

geätzte und ungeätzte REM-Aufnahmen einer 88,5Al8,5Fe1,3V1,7Si-Legierung;

Fig. 6

einen Probenquerschnitt durch eine AlFeCrTi-Legierung;

Fig. 7 bis 9

REM-Aufnahmen der AlFeCrTi-Legierung;

Fig. 10

eine LOM-Aufnahme der AlFeCrTi-Legierung;

Fig. 11

eine LOM-Aufnahme einer rasch abgekühlten AlFeCrTi-Legierung mit Restschmelze;

Fig. 12 und 13

LOM-Aufnahmen einer Al84,4Fe7Cr6Ti2,5Mg0,1-Legierung und

Fig. 14 bis 16

Versuchsergebnisse zum tribologischen Verhalten der Legierungen.

The invention will be explained in more detail with reference to embodiments and the accompanying drawings. Show it:

Fig. 1 to 3

Sample cross sections through AlFeVSi alloys;

4 and 5

etched and unetched SEM micrographs of a 88.5Al8.5Fe1.3V1.7Si alloy;

Fig. 6

a sample cross section through an AlFeCrTi alloy;

Fig. 7 to 9

SEM images of the AlFeCrTi alloy;

Fig. 10

a LOM image of the AlFeCrTi alloy;

Fig. 11

a LOM image of a rapidly cooled AlFeCrTi alloy with residual melt;

FIGS. 12 and 13

LOM images of an Al84.4Fe7Cr6Ti2.5Mg0.1 alloy and

Fig. 14 to 16

Test results on the tribological behavior of the alloys.

The following FIGS. 1 to 13 describe the manufacturing parameters with the then adjusting and the Gefugemorphologien of alloys of the invention based on AIFeVSi and AlFeCrTi in argon atmosphere.

Embodiment 1 AlFeVSi alloys

The Fig. 1-3 show sample cross-sections of AlFeVSi alloys cast under different conditions. The 12mm sample cross section out Fig. 1 shows an Al88.4Fe8.5V1.3Si1.7Zr0.1 alloy which was poured into a preheated to 600 ° C graphite mold at a melting temperature of 750 ° C and the Zr was added as a grain refining element. The sample cross section (14mm) Fig. 3 is based on an Al88.5Fe8.5V1.3Si1.7 alloy, which was poured without preheating in a graphite mold at a melting temperature of 700 ° C. Fig. 2 shows the same alloy but under the process variant that the melting temperature was 750 ° C and the graphite mold was heated to 500 ° C. The latter alloy offers an E modulus at room temperature (RT) of E ^RT = 85.7 GPa and at 500 ° C still E ^{500 ° C} = 65 GPa. Such values of the modulus of elasticity are that is comparable to that of a high-carbon, lamellar gray cast iron (~ 3.7% by weight C, GL11) and significantly larger than that of AlSi alloys. It should be noted for both exemplified Al-casting alloys according to the invention that the high moduli of elasticity were achieved without the addition of ceramic fibers, particles or platelets. Alone due to the high modulus of elasticity, the alloys according to the invention can substitute cast iron for material mechanics, since, in addition, it decreases in a similar manner with increasing temperature, as in the case of high-carbon cast iron. The decrease in strength of the alloys of the invention is also shifted to higher temperatures.

The Fig. 1-3 illustrate that the uniform formation of the microstructure of the Al88.5Fe8.5V1.3Si1.7 alloy over the cross section is achieved by a graphite mold preheated to 500 ° C, but these conditions promote the growth of large dendrites of Al ₃ Fe (X-ray diffraction index JCPDS NR .: 001-1265) of several millimeters in length. Only the grain refining with 0.1 wt .-% Zr, a preheated to 600 ° C graphite mold in conjunction with a casting temperature of 750 ° C achieves a much finer micrograph, which is pronounced homogeneous over the cross section.

In addition to the precipitation of "primary" dendrites of Al ₃ Fe (001-1265) and Al ₈₀ V ₁₂ Fe _7.5 (JCPDS No .: 040-1229) in the 88.5Al 8.5 Fe 1.3V 1.7Si alloy, FIGS SEM images of the Fig. 4 (unetched) and Fig. 5 (etched) the fine "pearlite" pattern from the eutectic decay of the residual melt, which consists of AlSi ₂ (aluminum disilicide). This forms the key to the formation of the high hot strength of a "classically" cast AlFe-XY alloy without the use of rapid solidification.

Embodiment 2 - AlFeCrTi alloys

Fig. 6 Figure 3 shows a grain morphology of an Al84.5Fe7Cr6Ti2.5 alloy cast at 700 ° C with no grain refining elements added to the alloy and casting into a non-preheated graphite mold (∅ = 14 mg). The alloy of Al84.5Fe7Cr6Ti2.5 has a modulus of elasticity of E ^RT = 104.1 GPa, which at 500 ° C drops to E ^{500 ° C} = 83 GPa.

The alloy system Al84,4Fe7,0Cr6,0Ti2,5 also exudes a dense, but closed, primary dendrite network (see Fig. 6 ), which was analyzed by EDX as an Al ₄ (Fe, Cr). In addition, the SEM images reveal ( Fig. 7 (Unetched); Figure 8 (etched)) precipitates of Al ₄ (V, Fe) in addition to the Al ₃ Fe dendrites. Within the lamellar drendrites one finds a globular substructure. In addition, one finds in the same microstructure further precipitates of Al ₃ (Ti, Cr) ( Fig. 9 ; SEM image, etched).

As with the 88.5Al8.5Fe1.3V1.7Si alloy, the AlFeCrTi alloy exhibits a fine, "pearlitic" pattern of eutectic disintegration of the residual melt of the Al84.4Fe7.0Cr6.0Ti2.5 alloy ( Fig. 10 ). For comparison shows Fig. 11 a LOM image of intermetallic lamellar dendrites in a rapidly cooled AlFeCrTi alloy with the residual melt.

By reducing the difference between casting and mold temperature to 250K and grain refining using 0.1 weight% Mg, the dendrite network in an Al84.4Fe7.0Cr6.0Ti2.5Mg0.1 alloy appears somewhat finer ( Fig. 12 ), which is caused in particular by their branching or ramification ( Fig. 13 ). The Al84.4Fe7.0Cr6.0Ti2.5Mg0.1 alloy was cast at 750 ° C into a graphite mold (14 mm) preheated to 500 ° C. The 88.5Al8.5Fe1.3V1.7Si alloys are more prone to forming star-shaped crystals as compared to the Al84.4Fe7.0Cr6.0Ti2.5Mg0.1 alloy with a dendrite network.

Overall, it has also been shown that the AlFeXY alloys according to the invention advantageously with a low excess temperature of max. 150K above the melting temperature of the alloy.

Tribological behavior

The off-engine characterization of the tribological behavior of the AlFeXY alloys according to the invention was carried out according to the BAM test technique, which is the reference " Woydt M. and N. Kelling, "Characterization of the Tribological Behavior of Lubricants and Materials for the Tribological System" Piston Ring / Cylinder Liner, in: ASTM STP 1404 "Bench testing of industrial fluid lubrication and use in machinery applications", June 2000 , Seattle, ISBN 0-8031-2867-3, p.153 "describes in detail. Fig. 14 shows the wear coefficient or rate of rotating samples of two AlFeXY and of different piston rings under mixed / boundary friction in first-fill straight oils SAE 0W-30 (FUCHS "PCX") or 5W-30 (Castrol "SLX") (F _N = 50 N, s = 24 km, T = 170 ° C). Both in Fig. 14 used AlFeXY alloys were vacuum cast and the intermetallic phases were not exposed by chemical or mechanical (honing) clipping.

The tribological functional surfaces were lapped at R _PK ~ 0.43 μm at Al88.4 Fe8.5 V 1.3 S.1.7 Zr0.1 and R _PK ~ 0.37 μm at Al84.4 Fe7.0 Cr6.0 Ti2.5 Mg0.1.

The Fig. 14 gives the results obtained in the form of the wear coefficient of the main body (piston ring) separated from the counter body (rotating sample or cylinder bore) with the belonging to the respective pairing mixed / boundary friction number again. In the Fig. 14 hydrocarbons based SAE 5W-30 and SAE 0W-30 oils have a high temperature high shear viscosity (HTHS) of 3.0 mPas. The GG20HCN is a 3.66 wt% carbon high carbon gray cast iron with lamellar graphite. The piston ring designations "MKP81A", "MKJet502 (WC / Cr ₃ C ₂ ," superpolished ")" and "CKS36" are brand names of Federal Mogul Burscheid GmbH. "Nitriert" means in the diagrams a "standard nitration" by the company Federal Mogul Burscheid GmbH. The atmospheric, plasma sprayed (APS) Ti _n O _2n-1 and Ti _n-2 Cr ₂ O _2n-1 ring coatings are experimental coatings for piston rings from CIE Automotive (Tarabusi, Barrio Urquizu 58, ES-48140 Igorre) AlFeXY alloys Al84.4Fe7.0Cr6.0Ti2.5Mg0.1 and 88.4Al8.5Fe1.3V1.7SiZr0.1 were vacuum degassed at 750 ° C in a graphite mold preheated to 600 ° C.

In the BAM test set, nitrided rings against AlSi17 (AlSi17Cu4Mg, "Alusil" from Kolbenschmidt) or AlSi25Ni4 ("Silitec" from PEAK Werkstoff GmbH) up to 25 N normal force are considered to be wear-resistant or wear in the low-wear position N (oil-dependent!) Go into the wear high position. The following table shows the mixing / friction coefficients of AlSi alloys (chemically released) in the BAM test setup (T = 170 ° C, s = 24 km, v = 0.3 m / s) compared to Al84,4Fe7Cr6Ti2, 5Mg0,1 to remove. PKW
piston ring career normal force
[N] Wear coefficient of raceway [10 ^-9 mm ³ / Nm] Engine oil nitrided GG20HCN 50 58 5W-30 Renault nitrided Al84,4Fe7,0Cr6,0 50 200 5W-30 Ti2,5Mg0,1 Renault nitrided Al84,4Fe7,0Cr6,0
Ti2,5Mg0,1 50 100 PPG32-2 nitrided Al84,4Fe7,0Cr6,0 50 80 5W-30 Ti2,5Mg0,1 ( "PCX") nitrided AlSi17Cu4Mg 25 7 0W-30 50 5000 ( "SLX") nitrided SILITEC (AlSi25) 12.5 1 5W-30 25 60 ( "PCX") 50 110 * First fill oil, ** Polypropylene glycol monobutyl ether motor oil formulation of BAM.

In the BAM test set, the average wear coefficient at F _N = 50 N of GGL20HCN is 4.8 10 ^-8 mm ³ / Nm on average from more than 200 trials with highly-carbonated gray cast iron GGL20HCN. The wear resistance of the Al84.4Fe7Cr6Ti2.5Mg0.1 alloy, which has been compounded with 0.1% by weight Mg, achieves wear resistance and load capacity comparable to high-carbon gray cast iron compared to the molybdenum-based MKP81A piston ring.

Conspicuous in the table are the higher coefficients of friction with the first filling oil SAE 5W-30 under mixed / boundary friction of the AlFeXY alloys compared to the GGL20HCN.

The relatively high mixed friction numbers can be reduced by the use of a polyalkylene glycol (PAG46-4 + 2.6 Phopani, HTHS = 3.6 mPas) or a polypropylene glycol monobutyl ether (PPG32-2 + 2.6 Phopani; HTHS = 2.87 mPas) ( please refer Fig. 15 ). The metal-free friction reducer contained in the first filling oil SAE 0W-30 ("PCX") with an HTHS of 3.0 mPas does not affect the AlFeCrTi. Underlined against a nitrided piston ring Fig. 15 in that the Al84,4Fe7,0Cr6,0Ti2,5Mg0,1 alloy on the track side, with the same normal force of F _N = 50 N, is comparable with the high carbon cast iron in terms of wear coefficient within the precision limits of the test method (s = 24 km; = 170 ° C). Especially in the PPG32-2, the total wear of the piston ring and raceway is comparable to that of GG20HCN.

Referred only to the "nitrided" piston ring shows Fig. 16 in that the AlFeVSi, but in particular the AlFeCrTi, in the oils FUCHS PCX 0W-30 and the polyglycol PPG32-2 + 2.6 Phopani has comparable wear resistance to the high-carbon gray cast iron GGL20HCN (FN = 50 N; s = 24 km; = 170 ° C). In Fig. 16 is still the wear coefficient of a long-term experiment (108 km) reproduced, whereby a strong, wear-reducing run-in behavior of AlFeCrTi alloy is documented.

Crankshaft plain bearing shells made of "eutectic" AlSi12CuNiMg (Karl Schmidt GmbH, KS 1275 (material number 3210.9), today Kolbenschmidt AG with 11-13.5% Si, 0.5-1.3 Cu, 0.8-1.3 Mg, 0.5-1.3 Ni, -0.25 Zn, ~ 0.1% Cr, balance Al) were used in the double-star BMW 801 aircraft engine (Ing. Buske, The dependence of the bearing load on the bearing design, Lubricant report -Tagung, Part 1: friction and wear, cold behavior, 11./12 12. 1941, Berlin-Adlershof, pp. 119-148), wherein the crankshaft journal made of a "nitriding steel" with HRC 58 was. Such a material solution has been uncommon in the automotive and construction machinery industry ever since. The current running surfaces of the sliding bearing shells made of AlSn14Cu8, AlSn20, PbSn10Cu3, GZ-CuSn7ZnPb or lead bronzes as well as anti-friction coatings require in the lubricants corrosion protection additives for federal metals, which significantly impair the ecotoxicological properties. On the whole, AlSi or AlFeXY alloys are less susceptible to corrosion and make it possible to avoid or significantly reduce the concentration of the corrosion protection additives. Known in the art is still an Al96 (Ni, Mn) alloy (Glyco-172) with a maximum allowable geometrical bearing pressure of 80 MPa, which is fatigue and corrosion resistant, but it tends to malfunction due to insufficient lubrication due to the AlFeXY metallurgy is suppressed.

The tribological limit load capacity of 100 MPa (geometrical surface pressure) of the sliding combination "AlSi12CuNiMg / Nitrierstahl" in the BMW801 double star engine at an oil inlet temperature of 99 ° C of the fully synthetic lubricant "SS-1600" based on an adipic ester and ethylene oil is noteworthy, since it with a kinematic Viscosity η _100C ~ 6.2 mm ² / s was still significantly "thinner" than today's Leichtiauföle with η _100C ~ 9-12 mm ² / s.

Another advantage of an AlFeXY system is that the wear protection and high-pressure additives in engine and gearbox oils, also due to the metallurgy of the test specimens in tribometer, are matched to iron and not to silicon.

Valve guides require high thermal diffusivity because they dissipate heat from the valve stem into the cylinder head, with associated wear resistance. Therefore, valve guides are preferably made of copper-based alloys, as CuZn36Mn3Al2SiPb (≅ CuZn40Al2 according to DIN 17660 or CW713R) with λ _RT -63 W / mK or K ^RT ~ 19.7 mm ² / s. Temperatures of 500 ° C are not uncommon on the surfaces in the lower part of the outlet valve guide. The aluminum alloys according to the invention offer a 3-4 times higher thermal diffusivity combined with the necessary temperature resistance without melt equilibria up to> 600 ° C.

Aluminum piston materials consist of AlSi12CuXX eutectic alloys or hypereutectic AlSi18CuXX alloys with up to 0.85% iron by weight. The thermal diffusivities are between 55 mm ² / s <K ^RT <61.7 mm ² / s.

Claims (11)

1. Use of a wear-resistant aluminium alloy produced by a method comprising the steps of:

   (i) providing an aluminium alloy of the composition

   Fe: 3-10;

   X: 3-10;

   Y: 0-1.5;

   Z: 0-10;

   wherein
   X represents an element or combination of elements

   (a) V and Si;

   (b) Cr and Ti;

   (c) Ce; or

   (d) Mn;

   in each case with the proviso that the proportion of the individual elements in the combinations of elements (a) and (b) is at least 0.5% by weight;
   Y represents one or more grain-refining elements selected from the group of B, Ce, Sr, Sc, Mg, Nb, Mn and Zr, unless these are already present as X;
   Z represents one or more ceramic additives increasing hot strength, selected from the group of fibres, particles and platelets; and
   where the figures are based on % by weight in terms of the alloy, and Al and also production-related impurities occupy the remaining proportion to 100% by weight of the alloy, with the proviso that the proportion of Al in the alloy is at least 80% by weight;

   (ii) melting the aluminium alloy, dissolving and homogenizing the alloy elements at temperatures of 650°C to 1000°C; and

   (iii) casting the melt into a casting mould at a casting temperature situated within a range beginning with a melting temperature of the alloy up to a temperature of 150°C above the melting temperature;

   for the production of sliding elements in crankshaft bearing shells, cylinder faces, piston rings, pistons, valve guides, bearing bushes or bearing shells.
2. Use according to Claim 1, wherein the casting temperature in step (iii) is situated within the range from 1°C to 80°C above the melting temperature of the alloy.
3. Use according to Claim 2, wherein the casting temperature in step (iii) is situated within the range from 10°C to 50°C above the melting temperature of the alloy.
4. Use according to any of the preceding claims, wherein a temperature of the casting mould is situated within the range from 450°C to 600°C.
5. Use according to any of the preceding claims, wherein the alloy comprises 4-8% by weight of Fe.
6. Use according to any of the preceding claims, wherein the alloy comprises 3-5% by weight of X.
7. Use according to any of the preceding claims, wherein the alloy comprises 0.5-0.8% by weight of Y.
8. Use according to any of the preceding claims, wherein X represents the combination of elements (a) and a proportion of Si is less than or equal to 2% by weight.
9. Use according to Claim 1, wherein X represents the combination of elements (a) and a proportion of Si is less than or equal to 1% by weight.
10. Use according to any of the preceding claims, wherein the steps (ii) and (iii) are part of a metallurgical melt casting process selected from the group of sand casting, pressure casting, continuous casting, thin-strip casting, centrifugal casting and cold crucible processes.
11. Crankshaft bearing shell, cylinder face, piston ring, piston, valve guide, bearing bush or bearing shell having a sliding element made of an aluminium alloy which is produced by a method comprising the steps of:

    (i) providing an aluminium alloy of the composition

    Fe: 3-10;

    X: 3-10;

    Y: 0-1.5;

    Z: 0-10;

    wherein
    X represents an element or combination of elements

    (a) V and Si;

    (b) Cr and Ti;

    (c) Ce; or

    (d) Mn;

    in each case with the proviso that the proportion of the individual elements in the combinations of elements (a) and (b) is at least 0.5% by weight;
    Y represents one or more grain-refining elements selected from the group of B, Ce, Sr, Sc, Mg, Nb, Mn and Zr, unless these are already present as X;
    Z represents one or more ceramic additives increasing hot strength, selected from the group of fibres, particles and platelets; and
    where the figures are based on % by weight in terms of the alloy, and Al and also production-related impurities occupy the remaining proportion to 100% by weight of the alloy, with the proviso that the proportion of Al in the alloy is at least 80% by weight;

    (ii) melting the aluminium alloy, dissolving and homogenizing the alloy elements at temperatures of 650°C to 1000°C; and

    (iii) casting the melt into a casting mould at a casting temperature situated within a range beginning with a melting temperature of the alloy up to a temperature of 150°C above the melting temperature.

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