WO2010036534A2

WO2010036534A2 - Turbocharger and adjustable blade therefor

Info

Publication number: WO2010036534A2
Application number: PCT/US2009/056916
Authority: WO
Inventors: Gerald Schall; Melanie Gabel
Original assignee: Borgwarner Inc.
Priority date: 2008-09-25
Filing date: 2009-09-15
Publication date: 2010-04-01
Also published as: KR101576194B1; WO2010036534A3; KR20110063658A; CN102149838A; DE112009002014B4; JP2012503719A; US20110182749A1; DE112009002014T5

Abstract

An adjustable blade for turbocharger applications, particularly in diesel engines, is described, which consists of an iron-based alloy with an austenitic basic structure with dendritic carbide precipitations.

Description

TURBOC~^TARGER AND ADJUSTABLE BLADE THEREFOR

DESCRIPTICK

The m\ent_on relates to an adjustaole b_ade for turoocharger applications, particularly in a diesel engine, according to the preamble of claim 1, and also to a" exhaust gas turbocharger with an adjustable blade, according to the preamble of claim 5.

Exhaust gas turbochargers are systems for increasing the power of piston engines. I^ an exhaust gas turbocharger, the energy of the exhaust gases is utilized for increasing the power. The power increase results from a rise m tne mixture throughput per working stroke.

A turbocharger consists essentially of an exhaust gas turjoine with a shaft and compressor, the compressor arranged i~ the intake tract of the engine being connected to the shaft, ana the blade wheels located m the casing of the exhaust gas turbine and m the compressor rotating. In a turJooc^arger with variable turome geometry, adjustaole blades are additionally mounted rotatably m a olade bearing r_^ng aid εtre moved by means of an adjustment ri^g arranged i" t^he turbine casing of the turoocharger .

The adjustable blεtdes, as they are known, have to satisfy eztremely stringent material requirements. The material forming the adjustable blades must be ^eat- resistant, that is to say still srow sufficient strength even at very h_gh temperatures of up to about 900⁰C. Furthermore, the material must haλ/e high wear resistance and also corresponding oxidation resistance, so that the corrosion or wear of the material is reαuceα, a^d, consequently, the resistance of the material under the extrene working conoitions is still ensured. Moreover, material is to be resistant to erosive attacks. These physical properties of the material are also to be reflected m the component , that is to say the adjustable blade.

Heat-resistant materials for exhaust gas turoochargers or their individual componeⁿts are known froir EP 1 396 620 Al. What is considered suitable here is a material which has a specific composition, the surface of the components being capable of being coatees, with a chrome carbide layer, and the material having a low fraction of small, non-metallic

. A heat resistance of the turbocharger or of its individual components of up to ^0O⁰ C or more is thereby to be achieved.

By contrast, the object of the present invention is to provide ar adjustable blade according to the preamble of claim 1 ana a turbocharger according to the preamble of da_ir 5, which have mproved temperature and oxidation resistance, and erosion resistance under extreme temperatures, and also a correspondirg wet corrosion resistance, which are distinguished by optimal tribological properties and, moreover, which exhibit a reouceo susceptibility to ^'wear.

The object is achieved by irears of t^he features of claim 1 and of claim 5.

Owing to the design according to the invention of an adjustaole blade or an exhaust gas turboc^harger comprising just such adjustable blades, a better temperature resistance of the component is achieved. This is also increased Joy a multiple by means of the dendritic carbide precipitations contained i" the iron- baseα alloy, that is to say a carbide microstructure contained m the iron-based alloy and having fine ramifications and, furthermore, dispersions of nitrogen m the form of nitride structures. An adjustable blade or an exhaust gas tυrbocharger is thus provided which contains the adjustable blades according to tne invention, which has optimal temperature ies_starce m the ra^ge of up to 900⁰C, furthermore is high_y heat- resistant, ras high wear, erosior ana corrosion resistance and, moreover, is also distiⁿguished oy very good slicing properties, along with reαuceα oxidizaoility .

Furthermore, the adjustable blade according to tne invention remains αimensionally stable and therefore highly planar, that is to say is distinguished by a high strength of the material forming it.

Without being involved in theory, it is presumed that caroide precipitations m the form of dendrites increase the stability of the iron-based alloy _^n that they form m the microstructure of the materia- fine ramifications w^hich perform a supportiⁿg action, so that the strength of the rrater_al and therefore the strength of the adjustable blade according to the invention are markedly increased on account of their unique structure. The dispersioⁿs of the element nitrogen m the form of nitπoe structures _n th_s case additionally increase the wear performance and corrosion resistance.

The material forming the adjustable blade according to the imention or the adjustable blade, moreover, exhibits optimal resistance to mtercrystalline coriosion .

The maximum wear rate of the adjustable blade according to the invention i" this case amouⁿts to _ess than 0.08 mm for a bearing load of 10 to about 18 N/mm , a sliding speed ot 0.0^25 n/s, a component temperature of about 500 to 9CO⁰C, a surface roughness Rz of 6.3, a test duration of 500 hours, a clock freq_^e^cy of 0.2 Hz, an adjustment angle of 45°, a coefficient of friction of 0.28, a journal diameter of 4.7 mm, a pressure pulsation of more than 200 rabar, and an exhaust gas pressure of more than 1.5 bar, in the case of a diesel exhaust gas as the test medium.

The material planeness of the adjustable blade according to the invention amounts to less than 0.1 mm, in the case of a circumference with the diameter of 80 mm, during a thermal shock cycle test with a test time of 300 hours.

The material of the adjustable blade according to the invention can be welded by means of conventional welding methods, such as WIG, plasma and also EB methods .

The subclaims contain advantageous developments of the invention .

In one embodiment, the adjustable blade is distinguished by a specific composition which contains the components C: 0.1 to 2O by weight, Cr: 18 to 43^ by weight, Ni: 5 to 15° by weight, Mn: 3 to lβ'o by weight, Si: < 1.3 -_c by weight, Nb: 0.5 to 4t by weight, N: 0.1 to 3% by weight, V: 0.2 to 2.Oo by weight, and Fe.

The influence of the individual elements on an iron- based alloy is known, but it was then found, surprisingly, that exactly the composition described produces a material which, when processed into an adjustable blade, has a particularly balanced property profile. As a result of this composition according to the invention, an adjustable blade with particularly high heat resistance εtnd temperature resistance, even up to 900⁰C, is obtained, which is distinguished by very good sliding properties and therefore low sliding wear or wear due to attrition. Moreover, the erosion - D - resistance is increased, as compared with known materials, and this also applies, furt^hermore, to wet corrosion. The material and therefore the adjustable blade according to the invention, moreover, are extremely dimerisiorially stable, and the material therefore has high strength ana deformation resistance.

These properties can be improved even further. For this purpose, according to one embodiment, tne adjustable blade according to the mve^tio" consists of a material which contains the following elements: C: 0.2 to 1.0 i by weight, Cr: 20 to 32¹I by weight, Ni: 7 to 14^fo by weight, Mn: 9 to 14.5c by weight, Si: < 1°^ by weight, Kb: 0.^5 to 3.5³, by weight, N: 0.1 to 1. C \ by weight, V: 0.3 to 1.6 o by weight, and Fe.

An adjustable Jolade produced m this way not only nas the high heat resistance of up to 900⁰C, but aloo markedly improved sliding properties. The sl_dmg wear is minimized here. Moreover, resistance to corrosion and erosion is maximized.. These properties accompany the very good deformation resistance and dimensional stability of the adjustable blade according to the invention at high temperatures .

A material produced m this way and therefore the adjustaole blade according to the _nvent_on thus have the following properties:

- D -

According to a further embodiment of the invention, the adjustable blade according to the invention or the material forming it, the iron-based alloy, is free of sigma phases. Sigma phases are brittle, intermetallic phases of high hardness. They arise when a body- centered cubic metal and a face-centered cubic metal, the atomic radii of which are identical with only a slight deviation, meet one another. Such sigma phases are undesirable because of their embrittling action and also on account of the property of the matrix to extract chrome. According to this further advantageous embodiment, therefore, the material according to the invention is distinguished in that it is free of sigma phases. This counteracts the embrittlement of the material and increases its durability. The reduction or avoidance of sigma phases is achieved in that the silicon content in the alloy material is lowered to less than 1.3"i by weight and preferably to less than IO by weight. Furthermore, it is advantageous here to employ austenite formers, such as, for example, manganese, nitrogen and nickel, if appropriate in combination .

Claim 5 defines, as an independently handleable article, an exhaust gas turbocharger which, as already described, comprises an adjustable blade which consists of an austenitic basic structure and which has or contains dendritic carbide precipitations.

Fig. 1 shows a perspective view, illustrated partially in section, of an exhaust gas turbocharger according to the invention. Fig. 1 illustrates the turbocharger 1 according to the invention which has a turbine casing 2 and a compressor casing 3 connected thereto via a bearing casing 28. The casings 2, 3 and 23 are arranged along an axis of rotation R. The turbine casing is shown partially in section, in order to make clear the arrangement of a blade bearing ring € ana a radially outer guide blade cascade 18 which is formeα by the latter ana which has a plurality of adjustable b_ades ⁿ distributed over the circumference and laviⁿg rotary axes ϋ. Nozzle cross sections are thereJoy formed, whicn are larger or smaller, depending on the positio" of t^e adjustable blades 7 , and whicr act upon the turbine rotor 4, located m the center on the axis of rotation R, to a greater or lesser extent with the eⁿgine exhaust gas supplied via a supply duct 9 a^d discharged via a central connection piece 10, m order via the turbine rotor 4 to drive a compressor rotor I^"7 seated on the same shaft.

In order to control the movements or the posit_on of the adjustable blades 7, an actuating device 11 _s provided. This may per se be of any desired design, but a preferred embodiment has a control casing 12 whicn controls the control movement of a tappet member 14 fastened to it, in order to convert the movement of said tappet member on an adjustment ring 5, located behind the blade oearing ring 6, into a slig^ht rotational movement: of said adjustment ring. Between the blade bearing ring € and an annular part 15 of the turbine casing 2, a free space I^ for the adjustable blades 7 is formed. So that this free space 13 can be safeguarded, the blade oearing ring 6 has spacers 16.

- Example -

A.n alloy, from which the adjustaole blades according to the _nveⁿtio" were formed, was produced from the following elements according to a customary method. The chemical analysis gav^ the following values for the elements: C: 0.2 to 0.5^ by weight; Cr: 23 to 26.5_O by weight; Ni: 9 to 13.5 \ by weight; Mn: 9 to 12.5 \ by weight; Si: max. 1.3°^ by weight; Nb: 0.75 to 1.75_O £>y weight; V: 0.7 to 1.6_O by weig^ht; N: 0.1 to 0.4 _o by weight, the rest: iron.

The adjustable blaaes proaucea according to this example were distinguished by a tensile strength R₁, of 687 MPa (ASTM E 8M/EK 1C002-1; at increased temperature: EN 10002-5). The yield point R_n 0.2 (measured according to standard methods) amounted to 317 MPa. The elongation at break of the material (measured according to standard methods) amouⁿted to 14.2°o. The hardness of the material (measured according to ASTM E 92/ISO 65C7-1) amounted to 258 HB. The coefficient of linear expansion (measured according to standard methods) amounted to 17.8 K^"" (20 to 900⁰T). The material was subjected to a validation test series which comprised the following tests:

outdoor exposure test changing climate test

- thermal shock test/cycle test - 300 h - hot gas corrosion test m a fission furnace

The component was distinguished in a±l the tests by excellent resistance to the acting forces. The mater_al therefore had extremely high wear resistance and outstanding oxidation resistance, so t^at corrosion a~d wear of the material under the specified conditions were markedly reduced, and, consequently, the resistance of the material was still ensured even over a long period of time.

Thermal cycle test:

The componeⁿt accoromg to the invention was subjected to a thermal cycle test, the thermal shocks being operated as follows: 1. use of stationary rotors;

2. 2-turbocharger operation;

3. test duration: 350 h (approximately 2000 cycles);

4. during the eⁿtire test, the exhaust gas flap m the turbochargers remains open at 15⁰C;

5. high temperature: nominal power point T3 = 75O⁰C, turbocharger mass flow on the turbine side: 0.5 kg/s;

6. low temperature: T3 = 100⁰C, turbocharger mass flow on the turbine side: 0.5 kg/s;

7. cycle duration: 2 x 5 min. (10 min.);

8. execution of three intermediate crack tests.

List of reference symbols

1 Turbocharger

2 Turbine casing

3 Compressor casing

4 Turbine rotor

5 Adjustment ring

6 Blade bearing ring

7 Adjustable blades

8 Rotary axes

9 Supply duct

10 Azial connection piece

11 Actuating device

12 Control casing

13 Free space for adjustable blades 7

14 Tappet member

15 Annular part of the turbine casing 2

16 Spacer/spacing boss

17 Compressor rotor

13 Guide blade cascade

28 Bearing casing

P Axis of rotation

Claims

PATENT CLAIMS

1. An adjustable blade for turbocharger application, particularly in diesel engines, consisting of an iron- based alloy with an austenitic basic structure and dendritic carbide precipitations.

2. The adjustable blade as claimed in claim 1, which contains the following components: C: 0.1 to 2i by weight, Cr: 18 to 43% by weight, Ni: 5 to 15^rό by weight, Mn: 8 to 16% by weight, Si: < 1.3* by weight, Nb: 0.5 to 4% by weight, N: 0.1 to 3% by weight, V: 0.2 to 2.Oi by weight, and Fe.

3. The adjustable blεtde as claimed in claim 1, which contains the following components :

C: 0.2 to 1.0% by weight, Cr: 20 to 32* by weight;

Ni : 7 to 141 by weight, Mn: 9 to 14.5i by weight,

Si: < 1% by weight, Nb: 0.75 to 3.5% by weight, N: 0.1 to 1.0% by weight, V: 0.3 to 1.6% by weight, and Fe.

4. The adjustable blade as claimed in claim 1, wherein the iron-based alloy is free of sigma phases.

5. An exhaust gas turbocharger, particularly for diesel engines, comprising an adjustable blade consisting of an iron-based alloy with an austenitic basic structure and dendritic carbide precipitations.

6. The exhaust gas turbocharger as claimed in claim

5, wherein the adjustable blade contains the following components :

C: 0.1 to 2¹-- by weight, Cr: IS to 43% by weight, Ni: 5 to 151 by weight, Mn: 8 to 16^rc by weight, Si < 1.3% by weight, Nb: 0.5 to 4% by weight, N: 0.1 to 3% by weight, V: 0.2 to 2.0° by weight, and Fe.

7. The exhaust gas turbocharger as claimed in claim 5, wherein the adjustable blade contains essentially the following components:

C: 0.2 to 1.01 by weight, Cr: 20 to 321 by weight, Ni: 7 to 14-- by weight, Mn: 9 to 14.51 by weight, Si: < 11 by weight, Nb: 0.75 to 3.51 by weight, N: 0.1 to 1.01 by weight, V: 0.3 to 1.61 by weight, and Fe.

S. The exhaust gas turbocharger as claimed in claim 5, wherein the material of the adjustable blade is free of sigma phases.