DE112012001811T5 - Turbocharger and component for this - Google Patents

Abstract

A component is described for turbocharger applications, especially in diesel engines, which consists of a ferritic base iron-based alloy containing a carbide and nitride structure.

Description

The invention relates to a component for turbocharger applications, in particular in a diesel engine, according to the preamble of claim 1, as well as an exhaust gas turbocharger with a component according to the preamble of claim 7.

Exhaust gas turbochargers are systems for increasing the performance of piston engines. In an exhaust gas turbocharger, the energy of the exhaust gases is used to increase performance. The increase in performance results from the fact that the mixture throughput per stroke is increased.

A turbocharger essentially consists of an exhaust gas turbine with a shaft and a compressor, wherein the compressor arranged in the intake tract of the engine is connected to the shaft, and the impellers located in the housing of the exhaust gas turbine and the compressor rotate. In a turbocharger with variable turbine geometry adjusting vanes are also rotatably mounted in a blade bearing ring and are moved by means of an adjusting ring arranged in the turbine housing of the turbocharger.

Extremely high material requirements are placed on the components of a turbocharger and, in particular, on its kinematics components, wastegate components or, in the case of a VTG turbocharger, also on its VTG components. The material of these components must be heat resistant, so even at very high temperatures of up to about 900 ° C still provide sufficient strength and thus dimensional stability. Furthermore, the material must have a high resistance to wear and a corresponding oxidation resistance, so that the corrosion or wear of the material is reduced even at high working temperatures of several hundred ° C, and thus ensures the resistance of the material under extreme working conditions.

Out DE 10 2004 062 564 A1 is a vane ring for a turbocharger with good temperature stability and low sliding wear known. In this type of vane ring, an austenitic material is used, an iron-based alloy that has a high sulfur content to improve the lubricity of the component. Due to the specific composition, the creep resistance of the material is increased and thus an increased dimensional stability of the blade bearing ring at temperatures of over 850 ° C is achieved.

In contrast, it is an object of the present invention to provide a component for turbocharger applications according to the preamble of claim 1 and a turbocharger according to the preamble of claim 7, which has improved temperature and oxidation resistance and thus also a very good dimensional stability and heat resistance, and corrosion resistance have, which are characterized by optimum tribological properties and also show a reduced susceptibility to wear.

The object is achieved by the features of claim 1 and claim 7.

The inventive design in the form of a component for turbocharger applications or an exhaust gas turbocharger comprising a similar component consisting of an iron-based alloy with ferritic structure containing a carbide and nitride structure, a better temperature resistance of the material and in particular improved Gleitschleleßeigenschaften and reduced tendency to oxidation is achieved , In the context of the invention, a carbide structure or nitride structure is understood to mean a microstructural carbide precipitation phase or nitride precipitation phase which is formed in the grain and at the grain boundaries of the iron-based alloy. The carbide structure is in particular a dendritic microstructure, whereby a very good resistance of the material and thus of the component to deformation and wear is obtained. Thus, a component for turbocharger applications or an exhaust gas turbocharger, which contains at least one component according to the invention provided, which has an optimum temperature resistance up to 900 ° C, is also highly heat-resistant, has high wear and corrosion resistance and, moreover, by very good sliding properties distinguished at reduced oxidation tendency, especially at the high operating temperatures.

Furthermore, the component according to the invention and thus the exhaust gas turbocharger according to the invention, even in continuous operation is dimensionally stable.

Without being bound by theory, it is believed that the presence of carbide precipitates and nitride precipitates in the ferritic iron-based alloy significantly increase the stability of the alloy material, and thus the component's stability, particularly against fretting wear, as well as its high temperature strength due to this unique structure.

For example, the iron-based alloy according to the invention, that is, the ferritic iron-base material with carbide and nitride structure forming the component, is characterized by a maximum sliding wear rate of 0.08 mm in diameter with a surface pressure of 20 MPa, a sliding speed of 0.0025 m / s, a component temperature about 850 ° C and 2,000,000 cycles, so an extraordinary resistance to fretting, out. In addition, the heat resistance, dimensional stability, and the high-temperature performance are improved.

The dependent claims have advantageous developments of the invention to the content.

Thus, in one embodiment, by the use of at least one of the elements tungsten (W), titanium (Ti) and niobium (Nb) in the ferritic iron-base alloy of which the component according to the invention is formed, the wear properties of the component, ie its resistance to frictional wear , be significantly improved. The elements W, Ti and Nb essentially form the carbide formations in the iron-based alloy, which in addition to the very good wear performance also increases the corrosion resistance of the material and thus of the component according to the invention.

In another embodiment, the turbocharger application component of the present invention is characterized by including at least one of C, W, Cr, Mn, Ti, V, Nb, and Si. The presence of at least one of these elements is to be understood as meaning that a similar element or a combination of these elements is used to produce the iron-based alloy, which is then processed into the component according to the invention. The elements added to the iron-based alloy can be in their original form, ie elementary, for example in the form of inclusions or precipitation phases, or in the form of their derivatives, ie in the form of a compound from the corresponding element, for. Example, as a metal carbide or metal nitride, are present, which form either in the production of the iron-based alloy or during the formation of the inventive component produced therefrom. The presence of the elements is directly detectable by conventional analytical methods in the component according to the invention.

The element carbon serves mainly to form the carbide structure according to the invention, ie the carbide precipitation phases and thus improves the strength of the material and the heat resistance thereof, and thus the component according to the invention for turbocharger applications. Also, the element tungsten increases, mostly by formation of carbidischen structures, the heat resistance and wear resistance of the material and contributes to its toughness. In particular, by combining tungsten with chromium and / or molybdenum, the corrosion resistance of the material in acidic media, as well as the hot corrosion performance can be significantly improved. The use of chromium thereby causes an increase in the hot tensile strength and scale resistance of the material. Chromium is also a strong carbide former, so that thus the wear properties of the material, and thus of the component according to the invention, are optimized. The use of the element chromium in the iron-based alloy, from which the component according to the invention is formed for turbocharger applications, has a further advantage: by the effect of high exhaust gas temperatures on the component, the chromium forms a Cr ₂ O ₃ cover layer, ie an oxidic cover layer on the component which efficiently promotes the resistance of the component to sliding friction and fretting under temperature stress. The use of manganese acts deoxidizing. It further forms the gamma region of the iron-base alloy and increases the yield strength and tensile strength of the material. In addition, manganese promotes the wear resistance of the component, especially at high operating temperatures. Vanadium refines the primary grain of the iron-based alloy during its production and thereby refines its cast structure. This achieves a high grain refinement which promotes the homogeneity of the iron-based alloy and permits its higher dynamic surface pressure of the material. In the iron-base alloy constituting the component of the present invention, the element niobium acts as a carbide former, thereby promoting the carbide structure in the grain and at the grain boundaries of the iron-base alloy. This also increases the heat resistance and creep strength of the material, and thus also the component according to the invention for turbocharger applications. Further, niobium promotes ferrite formation and reduces the gamma region of the iron-base alloy and can thus be used in a regulating manner. Silicon promotes the castability of the iron-based alloy by reducing the viscosity of the melt during casting. In addition, silicon in the material according to the invention promotes deoxidation, so that by adding this element, the resistance to hot corrosion is decisively improved. Thus, by suitable choice and combination of the elements, the properties of the iron-based alloy can be selectively controlled so that the component according to the invention for turbocharger applications and thus also of the exhaust gas turbocharger according to the invention, have a particularly balanced property profile. Other elements, as well as compounds, can be incorporated into the iron-based alloy.

According to a further embodiment, the component according to the invention for turbocharger applications is characterized in that it essentially contains the elements carbon (C) at 0.1 to 0.5 wt.%, In particular at 0.25 to 0.4 wt. , Chromium (Cr) with 15 to 22 wt .-%, in particular with 18 to 20 wt .-%, manganese (Mn) with a maximum of 1.3 wt .-%, in particular with at most 1 wt .-%, silicon (Si ) with 0.8 to 2.1 wt .-%, in particular with 1 to 1.8 wt .-%, niobium (Nb) with 0.4 to 1.3 wt .-%, in particular with 0.6 to 1 , 1 wt .-%, titanium (Ti) with 0.2 to 0.6 wt .-%, in particular with 0.3 to 0.5 wt .-%, tungsten (W) with 1.8 to 3.0 % By weight, in particular with 2 to 2.7% by weight, vanadium (V) with 0.3 to 1.0% by weight, in particular with 0.5 to 0.8% by weight, of nitrogen ( N) with a maximum of 3 wt .-%, in particular with a maximum of 2 wt .-% and iron (Fe) as the remainder. The respective amounts are based on the total weight of the iron-based alloy from which the component according to the invention is formed. As already stated, the presence of said elements is to be understood as being able to be present both elementally and in the form of one of their compounds in the iron-based alloy, and thus in the component according to the invention for turbocharger applications. In this embodiment, the abovementioned elements are essentially contained in the amounts specified in the component according to the invention. This means that unavoidable impurities may be present, but are preferably less than 2% by weight, and more preferably less than 1% by weight, based on the total weight of the iron-based alloy. The unavoidable residues or impurities thereby include, for example, aluminum (Al), nickel (Ni), zirconium (Zr), cerium (Ce), boron (B), phosphorus (P) and sulfur (S). The amounts of the individual elements can be detected directly by means of conventional elemental analytical methods in the component according to the invention.

It has surprisingly been found that it is precisely the combination described that produces a material, ie an iron-based alloy, which, when processed into a component for turbocharger applications, gives it a particularly balanced property profile. By means of this composition according to the invention, a component with particularly high hot strength, a temperature resistance of up to 900 ° C. and thus dimensional stability at high temperature is obtained, which is distinguished by outstanding sliding properties and thus a particularly low sliding wear. In addition, the corrosion resistance and oxidation resistance, especially at high operating temperatures, as they act when operating a turbocharger on the corresponding component, maximized.

Thus, a material produced in this way, from which the component according to the invention is formed, has the following properties: Mechanical property value measurement methods Tensile strength R _m > 650 MPa ASTM E 8M / EN 10002-1; at elevated temperature: EN 10002-5 Yield strength R _p0.2 > 270 MPa standard procedures elongation > 12% standard procedures hardness 225-265 HB ASTM E 92 / ISO 6507-1 Coefficient of linear expansion 10.5-14 K ^-1 (20 to 900 ° C) standard procedures

According to another embodiment of the invention, the component is substantially free of sigma phases for turbocharger applications. This applies in particular to the operation of the component according to the invention up to 900 ° C. This effectively counteracts the embrittlement of the material, thereby increasing the durability of the component. Sigma phases are brittle, intermetallic phases of high hardness. They arise when a cubic space-centered and a cubic-surface-centered metal meet whose atomic radii coincide with only slight deviation. Such sigma phases are undesirable because of their embrittling effect and also because of the property of the iron matrix to remove chromium. The iron-based alloy according to the invention and thus also the component according to the invention are essentially free of sigma phases, so that the unwanted effects described here are omitted. The reduction or avoidance of the formation of sigma phases is controlled in particular by targeted selection of the elements of the iron-based alloy and is achieved in particular by the silicon content in the alloying material being not more than 2.1% by weight and preferably not more than 1.8% by weight. , in each case based on the total weight of the iron-based alloy.

Thus, a component for turbocharger applications is described according to the invention, which is characterized by excellent wear performance, ie a high sliding wear resistance even at high temperatures of up to 900 ° C, high heat resistance and dimensional stability and also by excellent oxidation resistance and corrosion resistance. By this excellent Properties, the component according to the invention is particularly suitable for such components for turbocharger applications that are exposed to high temperatures of up to 900 ° C and / or high friction. Exemplary components include kinematic components, waste gate components and VTG components, and in particular VTG components and flap support members.

The production and processing of the iron-based alloy into the component according to the invention for turbocharger applications can be carried out by means of conventional methods. To ensure dimensional stability, an aging anneal can be performed at 900 ° C for about 2 hours followed by cooling in air to generate secondary precipitates. The material can be welded by TIG, plasma and EB welding.

As an independently tradeable object, claim 7 defines an exhaust gas turbocharger comprising at least one component as already described, which consists of an iron-based alloy with ferritic basic structure and contains a carbide and nitride structure.

The advantageous embodiments of the component according to the invention are also used in the embodiments of the exhaust gas turbocharger according to the invention.

1 shows a partially sectioned perspective view of an exhaust gas turbocharger according to the invention. In 1 is a turbocharger according to the invention 1 shown, which is a turbine housing 2 and a so about a bearing housing 28 connected compressor housing 3 having. The housing 2 . 3 and 28 are arranged along a rotation axis R. The turbine housing is shown partially in section to the arrangement of a vane bearing ring 6 and a radially outer guide grid formed by this 18 to illustrate that a plurality of circumferentially distributed adjusting blades 7 with rotary axes 8th having. As a result, nozzle cross-sections are formed, depending on the position of the adjusting blades 7 are larger or smaller and located in the middle of the axis of rotation R turbine rotor 4 more or less with the via a feed channel 9 fed and via a central neck 10 supplied exhaust gas of an engine to pass over the turbine rotor 4 a compressor rotor sitting on the same shaft 17 drive.

To the movement or the position of the adjusting blades 7 to control is an actuator 11 intended. This can be designed as desired, but a preferred embodiment has a control housing 12 on, which is the control movement of a ram member attached to it 14 controls its movement to one behind the blade bearing ring 6 located adjusting ring 5 in a slight rotational movement of the same implement. Between the vane bearing ring 6 and an annular part 15 of the turbine housing 2 becomes a free space 13 for the adjusting blades 7 educated. To this free space 13 to be able to secure, has the blade bearing ring 6 spacer 16 on.

- Example -

Unless otherwise indicated, the quantities of each element refer to the total weight of the iron-based alloy.

From the following elements, an iron-based alloy was made by a common method, from which several components of the invention for turbocharger applications, namely damper shaft, flap plate and bushing were formed. The chemical analysis gave the following values for the elements: C: 0.25 to 0.4 wt%, Cr: 18 to 20 wt%, Mn: less than 1 wt%, Si: 1 to 1 , 8% by weight; Nb: 0.6 to 1.1 wt.%, Ti: 0.3 to 0.5 wt.%, W: 2 to 2.7 wt.%, V: 0.5 to 0.8 wt In addition, traces of unavoidable residues of Al, Ni, Zr, Ce, B, P and S were found in trace amounts of less than 1% by weight ,

The components produced according to this example were characterized by the following properties: property Measured value (measuring method) Tensile strength R _m at 20 ° C 655 MPa (ASTM E 8M / EN 10002-1) Yield strength R _p 0.2 at 20 ° C 277 MPa (standard method) elongation 13.5% (standard procedure) hardness 248 HB (ASTM E 92 / ISO 6507-1) Coefficient of linear expansion at 20 ° C 12.6 K ^-1 (standard method) Heat resistance R _m at 900 ° C 123 MPa (EN 10002-5) Heat resistance R _m at 800 ° C 188 MPa (EN 10002-5) Heat resistance R _m at 700 ° C 257 MPa (EN 10002-5) Heat resistance R _m at 600 ° C 333 MPa (EN 10002-5) Heat resistance R _m at 500 ° C 395 MPa (EN 10002-5) Heat resistance R _m at 400 ° C 443 MPa (EN 10002-5) Yield strength R _p 0.2 at 900 ° C 83 MPa (standard method) Yield strength R _p 0.2 at 800 ° C 115 MPa (standard method) Yield strength R _p 0.2 at 700 ° C 174 MPa (standard method) Yield strength R _p 0.2 at 600 ° C 229 MPa (standard method) Yield strength R _p 0.2 at 500 ° C 281 MPa (standard method) Yield strength R _p 0.2 at 400 ° C 360 MPa (standard procedure)

• – Freibewitterungstest
• – Klimawechseltest
• – Thermoschocktest/Zyklustest-300 h
• – Heißgaskorrosionstest im Spaltofen
• – Strauss-Test nach DIN EN ISO 3651-2
• – Schwingungsreibverschleißprüfung am Tribometer: Buchse/Welle unter Betriebstemperatur (900°C)

The material was subjected to a validation test series which included the following tests:

• - Natural weathering test
• - Climate change test
• - Thermal shock test / cycle test-300 h
• - Hot gas corrosion test in cracking furnace
• - Strauss test according to DIN EN ISO 3651-2
• - Vibration wear test on the tribometer: bushing / shaft below operating temperature (900 ° C)

The respective component was distinguished in all tests by an excellent resistance to the forces acting on. The material thus had extremely high wear resistance and excellent oxidation resistance, so that corrosion or wear / friction wear of the material were significantly reduced under the specified conditions, and thus ensures the durability of the material and thus the component formed therefrom over a long time remained.

Thermal cycle test:

• 1. Verwendung feststehender Läufer;
• 2. 2-ATL-Betrieb;
• 3. Versuchsdauer: 350 h (ca. 2000 Zyklen);
• 4. Während des gesamten Versuchs bleibt die Abgasklappe bei den ATL's um 15° geöffnet;
• 5. Hohe Temperatur: Nennleistungspunkt T3 = 750°C, Massenstrom ATL turbinenseitig: 0,5 kg/s;
• 6. Niedrige Temperatur: T3 = 100°C, Massenstrom ATL turbinenseitig: 0,5 kg/s;
• 7. Zyklusdauer: 2 × 5 min. (10 min.);
• 8. Durchführung von drei Zwischenrissprüfungen.

The components according to the invention (shaft / bushing) were subjected to a thermocycling test, the thermal shocks being carried out as follows:

• 1. using fixed runners;
• 2. 2-ATL operation;
• 3. Duration of the test: 350 h (about 2000 cycles);
• 4. Throughout the experiment, the exhaust flap remains open at the ATL's by 15 °;
• 5. High temperature: rated power point T3 = 750 ° C, mass flow ATL turbine side: 0.5 kg / s;
• 6. Low temperature: T3 = 100 ° C, mass flow ATL turbine side: 0.5 kg / s;
• 7. Cycle time: 2 × 5 min. (10 min.);
• 8. Execution of three intermediate crack tests.

In the following load collective, the respective component according to the invention (shaft / bushing) was characterized by a low high-temperature oxidation, that is to say an oxidation rate of not more than 40 μm, in particular of not more than 35 μm, at a component temperature of 900 ° C. parameter Result bearing load 10-18 N / mm ² Sliding speed 0.0025 m / s component temperature 500-900 ° C surface roughness Rz 6.3 Test medium diesel exhaust Test duration 500 h clock speed 0.2 Hz displacement 45 ° coefficient of friction <0.18 Journal diameter 4.7 mm pressure pulsation > 200 bar exhaust gas pressure 1.5 bar wear rate <0.08 mm

The results given here prove that the component according to the invention is best suited for turbocharger applications in a temperature range of up to 900 ° C.

LIST OF REFERENCE NUMBERS

1

turbocharger

2

turbine housing

3

compressor housing

4

turbine rotor

5

adjusting

6

Nozzle ring

7

adjusting blades

8th

swiveling axes

9

feed

10

Axialstutzen

11

actuator

12

control housing

13

Free space for vanes 7

14

plunger member

15

annular part of the turbine housing 2

16

Spacer / spacer cams

17

compressor rotor

18

guide grid

28

bearing housing

R

axis of rotation

Claims (10)

Component for turbocharger applications, in particular in diesel engines, consisting of an iron-based alloy with ferritic basic structure containing a carbide and nitride structure. Turbocharger application component according to claim 1, comprising at least one of the elements selected from: W, Ti and Nb. A turbocharger application component according to claim 1 or 2, comprising at least one of C, W, Cr, Mn, Ti, V, Nb and Si. Component for turbocharger applications according to one of the preceding claims, characterized in that it contains substantially the following elements: C: 0.1 to 0.5 wt .-%, in particular 0.25 to 0.4 wt .-% Cr: 15 to 22 wt .-%, in particular 18 to 20 wt .-% Mn: ≤ 1.3 wt .-%, in particular ≤ 1 wt .-% Si: 0.8 to 2.1 wt .-%, in particular 1 to 1 , 8 wt .-% Nb: 0.4 to 1.3 wt .-%, in particular 0.6 to 1.1 wt .-% Ti: 0.2 to 0.6 wt .-%, in particular 0.3 to 0.5% by weight W: 1.8 to 3.0% by weight, in particular 2 to 2.7% by weight V: 0.3 to 1.0% by weight, in particular 0.5 to 0.8% by weight N: ≦ 3% by weight, in particular ≦ 2% by weight, and Fe: add. 100% by weight. Component for turbocharger applications according to one of the preceding claims, characterized in that it is substantially free of sigma phases. Component for turbocharger applications according to one of the preceding claims, characterized in that the component is a kinematic component and / or a waste gate component and / or a VTG component, in particular a VTG component and / or a flap carrier part. Exhaust gas turbocharger, in particular for diesel engines, comprising at least one component consisting of an iron-based alloy having a ferritic basic structure containing a carbide and nitride structure. Exhaust gas turbocharger according to claim 7, wherein the component comprises at least one of the elements selected from: W, Ti and Nb and in particular at least one of the elements selected from: C, W, Cr, Mn, Ti, V, Nb and Si. Exhaust gas turbocharger according to claim 7 or 8, characterized in that the component contains substantially the following elements: C: 0.1 to 0.5 wt .-%, in particular 0.25 to 0.4 wt .-% Cr: 15 to 22 Wt .-%, in particular 18 to 20 wt .-% Mn: ≤ 1.3 wt .-%, in particular ≤ 1 wt .-%, Si: 0.8 to 2.1 wt .-%, in particular 1 to 1 , 8 wt .-% Nb: 0.4 to 1.3 wt .-%, in particular 0.6 to 1.1 wt .-% Ti: 0.2 to 0.6 wt .-%, in particular 0.3 to 0.5% by weight W: 1.8 to 3.0% by weight, in particular 2 to 2.7% by weight V: 0.3 to 1.0% by weight, in particular 0.5 to 0.8% by weight N: ≦ 3% by weight, in particular ≦ 2% by weight, and Fe: add. 100% by weight. Exhaust gas turbocharger according to one of claims 7 to 9, characterized in that the component is substantially free of sigma phases.

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