U.S. patent application number 10/506737 was filed with the patent office on 2005-08-04 for metal-ceramic composites for tribological uses and defined sliding/friction pairs based on said materials.
Invention is credited to Lenke, Ilka, Meier, Gerd.
Application Number | 20050166708 10/506737 |
Document ID | / |
Family ID | 27789728 |
Filed Date | 2005-08-04 |
United States Patent
Application |
20050166708 |
Kind Code |
A1 |
Meier, Gerd ; et
al. |
August 4, 2005 |
Metal-ceramic composites for tribological uses and defined
sliding/friction pairs based on said materials
Abstract
The friction heat generated between both sliding pairs and
friction pairs has to be swiftly dissipated in older to maintain a
lubricant film or ensure constant coefficients of friction. The
invention consequently relates to metal-ceramic composites for
friction/sliding uses, which are characterized by basic
compositions containing 30 to 75 percent by volume of one or
several metallic phases, preferably aluminum and the alloys
thereof, and 25 to 70 percent by volume of one or several
non-metallic inorganic component/s as ceramic materials, preferably
silicon carbide, aluminum oxide, titanium oxide, and silicates.
Inventors: |
Meier, Gerd; (Leinburg,
DE) ; Lenke, Ilka; (Plochingen, DE) |
Correspondence
Address: |
FULBRIGHT & JAWORSKI, LLP
666 FIFTH AVE
NEW YORK
NY
10103-3198
US
|
Family ID: |
27789728 |
Appl. No.: |
10/506737 |
Filed: |
March 24, 2005 |
PCT Filed: |
February 19, 2003 |
PCT NO: |
PCT/EP03/01658 |
Current U.S.
Class: |
75/235 ; 148/437;
75/236 |
Current CPC
Class: |
B22F 2207/20 20130101;
B22F 2998/00 20130101; F16D 69/027 20130101; C22C 29/00 20130101;
B22F 2998/00 20130101; F16D 69/02 20130101 |
Class at
Publication: |
075/235 ;
075/236; 148/437 |
International
Class: |
C22C 029/02; C22C
029/12 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 5, 2002 |
DE |
10209476.4 |
Feb 14, 2003 |
DE |
10306096.0 |
Claims
1-18. (canceled)
19. A metal-ceramic composite for friction/slide application,
comprising a base composition comprising at least one metallic
phase in a proportion of 30 to 75 vol. % and at least one
non-metallic inorganic component in a proportion of 25 to 70 vol. %
as a ceramic material the composite having a thermal conductivity
greater than 50 W/mK, a flexural strength of about 300 MPa and a
modulas of elasticity of at least 160 GPa.
20. A metal-ceramic composite according to claim 19, wherein the
composition contains 40 to 60 vol. % of Al.sub.2O.sub.3 and 60 to
40 vol. % of Al.
21. A metal-ceramic composite according to claim 20, wherein the
thermal conductivity is greater than 50 W/mK, the flexural strength
is about 300 MPa and the modulus of elasticity is about 160
GPa.
22. A metal-ceramic composite according to claim 19, wherein the
composition contains 60 to 80 vol. % of SiC and 40 to 20 vol. % of
Al.
23. A metal-ceramic composite according to claim 22, wherein the
thermal conductivity is at least 180 W/mK, the flexural strength is
about 300 MPa and the modulus of elasticity is about 200 GPa.
24. A metal-ceramic composite according to claim 19, wherein the
surfaces in contact with a friction/slide partner have an Ra value
below 1 .mu.m.
25. A sliding ring comprising a metal-ceramic composite of claim
19.
26. A slide/friction pairing comprising a metal-ceramic composites
according to claim 1, wherein the pairings comprise one partner
consisting of a metal-ceramic composite (MCC) and one partner
consisting of MCC, carbon, Al.sub.2O.sub.3, SSiC, hard metal (HM),
ZTA (Al.sub.2O.sub.3 and ZrO.sub.2) or plastic, optionally
fibre-reinforced.
27. A slide/friction pairing according to claim 26, selected from
the group consisting of MCC/carbon, MCC/Al.sub.2O.sub.3, MCC/SSiC,
MCC/MCC, MCC/HM and MCC/ZTA (Al.sub.2O.sub.3+ZrO.sub.2).
28. A slide/friction pairing according to claim 26, selected from
the group consisting of MCC/carbon, MCC/Al.sub.2O.sub.3, MCC/SSiC,
MCC/MCC, MCC/HM and MCC/plastic, optionally fibre-reinforced.
29. A slide/friction pairing according to claim 26, selected from
the group consisting of MCC/carbon, MCC/SSiC, MCC/Al.sub.2O.sub.3,
MCC/MCC, MCC/HM and MCC/ZTA.
30. A slide/friction pairing according to claim 26, selected from
the group consisting of MCC/SSiC, MCC/Al.sub.2O.sub.3, MCC/MCC,
MCC/HM and MCC/ZTA.
31. The metal-ceramic composite of claim 19, wherein said at least
one metallic phase comprises aluminum or an aluminum alloy.
32. The metal-ceramic composite of claim 19, wherein said ceramic
material is selected from the group consisting of silicon carnie,
aluminum oxide, titanium oxide and a silicate.
Description
[0001] The invention relates to metal-ceramic composites for
slide/friction applications in which, to guarantee or improve
performance, the materials/material combinations used have a high
thermal conductivity and/or produce low frictional heat and/or tend
to have low static friction, and to defined slide/friction pairings
based on these composites.
[0002] For both slide pairings and friction pairings, the
frictional heat produced must be dissipated rapidly away from the
friction/slide region. This is necessary in order to maintain a
lubricating film or guarantee constant coefficients of friction.
The slide pairings used according to the state of the art,
especially in the mixed friction region or for dry running, are
based on silicon carbide against carbon, as described e.g. in W.
Tietze, Handbuch Dichtungspraxis, 2nd edition, Vulkan-Verlag,
2000.
[0003] The low thermal conductivity of carbon, e.g. 8 to 17 W/mK
according to the material characteristics from Schunk
Kohlenstofftechnik GmbH, Technologien in Kohlenstoff,
Geschaftsbereich 1, Lager-und Dichtungs-technik,
Werkstoffkennwerte, Standardwerkstoffe, Schunk, 30.14 (1997), can
lead to a noticeable temperature increase in the gap. Such a
temperature increase gives rise to thermal stressing of the binder
system and the impregnation, which can cause changes in the
materials, these in turn leading to unfavourable slide conditions.
The tribological properties can become impaired despite the very
good thermal conductivity of silicon carbide of e.g. 80 to 130
W/mK.
[0004] Temperature increases in the slide partners affect the fluid
in the gap and modify the friction/slide conditions. Solubilizers
can crystallize out due to the temperature change, which, after a
period of rest, increases the breakaway/starting torque and, in the
worst case, leads to seizure of the slide pairing.
[0005] This can occur both with rotating sealing units and with
those undergoing translational movement.
[0006] Low mechanical values such as the tensile strength, flexural
strength and hardness of a slide partner, for example carbon with
values of 30 to 80 MPa, additionally restrict the range of uses of
the above-mentioned sealing units. Fillers, particularly
impregnations, may be partially attacked. Chemically aggressive
media cause the impregnations to swell and thereby change the
tribological conditions. This is a further possible cause of a
temperature increase in the gap.
[0007] Temperature and pressure change the geometry and hence the
original setting of a slide pairing, which as a rule impairs
performance.
[0008] The object of the present invention is to provide a
favourable friction/slide system which meets the following
requirements: constant friction/slide properties, high thermal
conductivity, dimensional stability due to high modulus of
elasticity, and high strength.
[0009] This object is achieved by selecting specific materials and
material pairings.
[0010] Materials according to the invention that have the requisite
properties include metal-ceramic composites, or MCCs, consisting of
one or more metallic phases in a proportion of 30 to 75 vol. % and
one or more non-metallic inorganic components in a proportion of 25
to 70 vol. %. Preferred metallic phases are aluminium and its
alloys. The non-metallic ceramic components are ceramic materials,
preferably silicon carbides, aluminium oxides, titanium oxides and
silicates.
[0011] One of the preferred MCCs, based on Al.sub.2O.sub.3 and Al,
has a composition of 40 to 60 vol. % of Al.sub.2O.sub.3 and 60 to
40 vol. % of Al with a thermal conductivity of >50 W/mK, a
flexural strength of e.g. 300 MPa and a modulus of elasticity of
e.g. 160 GPa.
[0012] Another preferred MCC, based on SiC and Al, has a
composition of 60 to 80 vol. % of SiC and 40 to 20 vol. % of Al
with a thermal conductivity of e.g. 180 W/mK, a flexural strength
of e.g. 300 MPa and a modulus of elasticity of e.g. 200 GPa.
[0013] Metal-ceramic composites with a metal content of more than
50 vol. % are called metal-matrix composites (MMCs). If the ceramic
content is more than 50 vol. %, the materials are called
ceramic-matrix composites (CMCs).
[0014] Surface finishes with Ra values below 1 .mu.m are achieved
on the machined operating surfaces. However, these can be varied by
means of appropriate hard machining processes and thus optimized
according to the friction partner.
[0015] The heat build-up in friction/slide applications is reduced
by the choice of materials for the MCCs and by the surface finish.
In addition, the heat generated in the sealing gap is rapidly
dissipated to the surroundings by virtue of the high thermal
conductivity of the materials. The sealing gap temperature is
thereby lowered and cracking, efflorescence and deposition in the
sealing gap are substantially reduced, resulting in more favourable
and more constant coefficients of friction and abrasion
factors.
[0016] Moreover, the improved dimensional stability reduces the
possibility of edge running. This lowers the temperature peaks and
produces more stable fluid films in the sealing gap, which in turn
reduces the frictional activity and heat build-up.
[0017] In so-called hard/soft pairings, replacement of the softer
partner, for example carbon or plastic, by a ceramic material or a
composite results in improved mechanical properties for the whole
system and thereby expands the possible uses. Furthermore, the
tribological conditions are improved by avoiding friction partners
which tend to swell and/or behave in a critical manner towards
chemical attack. The pairing can thus be designed with narrower
tolerance limits than the materials used hitherto.
[0018] In so-called hard/hard pairings, the dry running or the
emergency running properties of the tribological pairings are
improved by using MCCs.
[0019] Reducing the abrasion lengthens the life of the friction
pairings and extends the service intervals.
[0020] Using the materials and material pairings according to the
invention brings decisive improvements in the industrial sector,
especially in the automotive industry and consumer goods
industry.
[0021] In general, by specifically designing the material with a
chosen combination of ceramic and metal in the penetration
structure, it is possible to adapt the tribological properties of
the pairings for the applications listed below by way of
example.
[0022] Axial face seals in cooling water pumps, especially
MCC/carbon, MCC/Al.sub.2O.sub.3, MCC/SSiC, MCC/MCC, MCC/HM (hard
metal), MCC/ZTA (Al.sub.2O.sub.3+ZrO.sub.2)
[0023] Axial face seals in dishwashing machines, especially
MCC/carbon, MCC/Al.sub.2O.sub.3, MCC/SSiC, MCC/MCC, MCC/HM,
MCC/plastic, optionally fibre-reinforced.
[0024] Axial face seals in direct fuel injection pumps, especially
MCC/carbon, MCC/SSiC, MCC/Al.sub.2O.sub.3, MCC/MCC, MCC/HM,
MCC/ZTA.
[0025] Axial face seals in CO.sub.2 compressors, especially
MCC/SSiC, MCC/Al.sub.2O.sub.3, MCC/MCC, MCC/HM, MCC/ZTA.
[0026] Defined slide/friction pairings between braking, bearing,
sealing or drive units, for example in lifts, escalators, cranes,
dry couplings, pumps and compressors, pistons and cylinders, swash
plates, radial bearings or axial bearings, bearings of grinding
cylinders, and slide partners for rotary shaft seals.
[0027] Choosing the materials of the friction partners specifically
in each case opens up new fields of application, especially in
lubricant-free areas of use, e.g. in the pharmaceutical and
cosmetic industry or in food technology.
[0028] The materials according to the invention are recommended as
friction partners particularly in cases where, after periods of
rest, the problem of seizure or deposition in the sealing gap
occurs and increases the breakaway torque, said materials being
used e.g. as gaskets for espresso machine fittings, sanitary ware
fittings and industrial fittings or for shut-off valves.
[0029] Other possible applications are side plates in fuel pumps or
power-assisted steering pumps. Apart from abrasion resistance,
these applications require in particular a high dimensional
stability, which is guaranteed by virtue of the low contraction of
the components. This increases the efficiency of the pumps,
enabling smaller, more compact and lighter designs to be used.
[0030] One possible use is as rollers and/or bearing units, e.g. in
combustion engines, compressors or exhaust valves.
[0031] Use in highly stressed valve drives, such as those present
in diesel engines, represents an alternative to today's expensive
solutions.
[0032] As a rule, slide units are specially constructed according
to the client's drawings and specifications. Typical dimensions for
mass-produced sliding rings are as follows: external diameter: 18
to 28 mm, internal diameter: 8 to 20 mm, and height: 2 to 5 mm.
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