GB2272959A - Hard wearing surfaces for piston grooves - Google Patents
Hard wearing surfaces for piston grooves Download PDFInfo
- Publication number
- GB2272959A GB2272959A GB9323865A GB9323865A GB2272959A GB 2272959 A GB2272959 A GB 2272959A GB 9323865 A GB9323865 A GB 9323865A GB 9323865 A GB9323865 A GB 9323865A GB 2272959 A GB2272959 A GB 2272959A
- Authority
- GB
- United Kingdom
- Prior art keywords
- piston
- coating
- aluminium
- cobalt
- ring groove
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02F—CYLINDERS, PISTONS OR CASINGS, FOR COMBUSTION ENGINES; ARRANGEMENTS OF SEALINGS IN COMBUSTION ENGINES
- F02F3/00—Pistons
- F02F3/10—Pistons having surface coverings
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
- C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
- C23C18/31—Coating with metals
- C23C18/32—Coating with nickel, cobalt or mixtures thereof with phosphorus or boron
- C23C18/34—Coating with nickel, cobalt or mixtures thereof with phosphorus or boron using reducing agents
- C23C18/36—Coating with nickel, cobalt or mixtures thereof with phosphorus or boron using reducing agents using hypophosphites
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16J—PISTONS; CYLINDERS; SEALINGS
- F16J9/00—Piston-rings, e.g. non-metallic piston-rings, seats therefor; Ring sealings of similar construction
- F16J9/26—Piston-rings, e.g. non-metallic piston-rings, seats therefor; Ring sealings of similar construction characterised by the use of particular materials
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
- F05C—INDEXING SCHEME RELATING TO MATERIALS, MATERIAL PROPERTIES OR MATERIAL CHARACTERISTICS FOR MACHINES, ENGINES OR PUMPS OTHER THAN NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES
- F05C2201/00—Metals
- F05C2201/02—Light metals
- F05C2201/021—Aluminium
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
- F05C—INDEXING SCHEME RELATING TO MATERIALS, MATERIAL PROPERTIES OR MATERIAL CHARACTERISTICS FOR MACHINES, ENGINES OR PUMPS OTHER THAN NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES
- F05C2201/00—Metals
- F05C2201/04—Heavy metals
- F05C2201/0433—Iron group; Ferrous alloys, e.g. steel
- F05C2201/0448—Steel
Landscapes
- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Combustion & Propulsion (AREA)
- General Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Chemically Coating (AREA)
Abstract
A surface of a piston ring groove of a piston made of aluminium or of aluminium alloy is provided with a hard wearing surface having a hardness in the range 300 to 750 Hv by applying a coating of cobalt by electroless plating. The coating may contain phosphorus and may be heat-treated after application.
Description
HARD WEARING SURFACES FOR PISTONS
This invention is concerned with the provision of hard wearing surfaces for pistons.
The pistons of internal combustion engines are often made of aluminium or an alloy thereof which is a relatively soft material compared to the iron or steel used to make the piston rings which seal the gap between the piston and the wall of its cylinder. The piston rings are received in grooves in the piston and, because of the differential in hardness, the surfaces of such grooves are prone to wear.
This problem is particularly acute in the case of the top ring groove, i.e. the groove nearest to the crown of the piston which borders the combustion chamber of the engine.
It has long been recognised that it is desirable to provide the top ring groove with one or more hard wearing surfaces to reduce the problem of wear. It is known, for example, to provide an insert of harder material, e.g. cast iron, which is cast into the piston so that it provides one or more surfaces of the top ring groove. The insert may be porous so that it is infiltrated by the metal forming the bulk of the piston or the insert may be pre-treated to improve its adherence to aluminium or an alloy thereof, e.g. the insert may be placed in a bath of molten aluminium to form thereon a layer which includes aluminium-iron intermetallic compounds. The use of an insert, while generally successful in reducing wear, has the disadvantages that the manufacturing process is made considerably more complex, the insert may become detached in service, and the weight of the piston is increased.
Other techniques for providing a hard wearing surface for pistons in the ring groove regions involve local alloying of the basic piston alloy, and surface treatments such as anodising. These techniques have not proved as successful as use of an insert. Anodising, for example, produces a rough surface which is generally unacceptable.
It has been suggested (see JP 4,119,265) that piston parts should be given a coating of a cobalt-tungstenphosphorus alloy by electroless plating to achieve a coating of hardness above 800 Hv which after heat treatment becomes 900 to 1200 Hv. Such a coating is considered to be too hard for piston ring grooves and likely to damage cooperating parts.
It is an object of the present invention to provide a method of providing a hard wearing surface as aforesaid which is simpler than using an insert as mentioned above.
The invention provides a method of providing at least one surface of a piston ring groove of a piston made of aluminium or aluminium alloy with a hard wearing surface having a hardness in the range 300 to 750 Hv, the method comprising applying a coating of cobalt or cobalt and phosphorus to said surface by electroless plating.
A method according to the invention is simpler than use of an insert as no positioning of an insert in a mould is involved. Furthermore, a uniform coating with an accurate thickness can be achieved reducing machining of the piston and scrap rates. The coating may be applied to all surfaces of a piston ring groove, e.g. the top ring groove. The coating may also be applied to several ring grooves and surfaces between the grooves.
Preferably, the phosphorus content of the coating is between 1% and 10% by weight, e.g. about 4%.
In order to increase its hardness, the coating may be heat-treated at a temperature between 1500C and 5000C.
This heat treatment may be for at least 30 minutes.
However, no specific heat treatment is necessary in some cases or the elevated temperatures at which the piston operates may have the effect of a heat treatment.
Preferably, a method according to the invention comprises immersing the surface to be coated in an aqueous solution of cobalt ions, catalyst, reducing agent, complexing agent and bath stabiliser. The thickness of the coating is found to be substantially directly dependent on the immersion time and may be between 6 and 40 microns. A thickness of about 6 microns was found to produce less wear than one of 18 microns when heat treated at 400or. Heat treatment at 1500C results in both coating thicknesses having substantially the same wear. The ring groove area and the crown of the piston may be coated by immersing only the top portion of the piston (with the piston inverted) or, if desired, regions not to be coated may be masked.
The aqueous solution is preferably maintained at a temperature above 850C, e.g. between 900 and 950C, as the deposit rate is good at these temperatures.
In order to achieve a smooth coating, the pH value of the aqueous solution is preferably between 8.5 and 10.5.
It was found that use of ammonium hydroxide as a bath stabiliser gave smoother deposits than when sodium hydroxide was used.
It was found that some piston samples required the aluminium or aluminium alloy to be activated before immersion in the aqueous solution. This can be achieved by immersing in zincate solution.
The method may comprise dipping the crown region of the piston into the aqueous solution while keeping the skirt region of the piston out of the solution.
The invention also provides a piston made of aluminium or aluminium alloy having a hard wearing coating having a hardness in the range 300 to 750 Hv on at least one surface of a piston ring groove thereof, the coating comprising cobalt deposited by electroless plating.
There now follows a detailed description of an illustrative example of a method according to the invention.
The illustrative example is a method of providing all the surfaces of a piston ring groove of a piston made of aluminium alloy with a hard wearing surface in the form of a coating of cobalt. The method also applies the coating to other areas of the piston. The groove in question is the top ring groove of the piston.
In the illustrative method, an aqueous solution containing cobalt ions is prepared using the following formulation:
Cobalt chloride heptahydrate 30g/L
Sodium hypophosphite 20g/L (reducing agent)
Sodium citrate 20g/L (complexing agent)
Ammonium chloride 50g/L (catalyst)
Ammonium hydroxide Sufficient to bring pH
to 9 to 10. (bath
stabiliser)
In this solution, cobalt ions were catalytically reduced to the metal in alkaline solutions by the hypophosphite ions which were thereby oxidised to orthophosphate ions.
The aluminium alloy surface was activated with zincate solution following vapour degreasing, alkali cleaning and acid desmutting. The activation involved dipping the piston into a zincate-bondal dip at 20 to 250C for 45 seconds.
The ring groove region and the crown of the piston were then immersed in the aqueous solution for 90 minutes with the temperature of the solution being maintained above 900C.
The piston was removed from the solution and rinsed and dried. The area of the piston immersed was found to have a coating thereon including on the radial faces of the ring groove. The coating had, therefore, been applied by electroless plating.
The coating was of smooth appearance and was very uniform in thickness including over the corners at the top and bottom of the ring groove. The coating was 18-20 microns in thickness on the complete section of the ring groove and was made up of cobalt with 1.5% by weight of phosphorus.
The coating was then subjected to a heat-treatment at 4500C for 90 minutes. This heat-treatment increased the hardness of the coating from an as-deposited value of 360 + 20 Hv. to 710 + 30 Hv. This is attributed to a transformation of the amorphous cobalt-phosphorus alloy to a dispersion of Co2P in a cobalt matrix.
The piston was then subjected to wear tests and found to produce less wear than conventional pistons with inserts at engine operating temperatures. The weight loss at 250 0C for conventional pistons in a 4 hour test was 6.9mg whereas that for the piston of the illustrative example was 4.4mg.
This test was under a load of 1.35kg and with no lubrication.
Claims (13)
1 A method of providing at least one surface of a piston
ring groove of a piston made of aluminium or aluminium
alloy with a hard wearing surface having a hardness in
the range 300 to 750 Hv, the method comprising
applying a coating of cobalt or cobalt and phosphorus
to said surface by electroless plating.
2 A method according to Claim 1, wherein the coating has
a phosphorus content between 1% and 10% by weight.
3 A method according to either of Claims 1 and 2,
wherein the coating is heat-treated at a temperature
of between 150 and 5000C.
4 A method according to Claim 3, wherein the heat
treatment is for at least 30 minutes.
5 A method according to any one of Claims 1 to 4,
wherein the method comprises immersing said surface in
an aqueous solution of cobalt ions, catalyst, reducing
agent, complexing agent and bath stabiliser.
6 A method according to Claim 5, wherein the solution is
maintained at a temperature above 850C.
7 A method according to either one of Claims 5 and 6,
wherein the pH level of the solution is between 8.5
and 10.5.
8 A method according to any one of Claims 5 to 7,
wherein the surface of the aluminium or aluminium
alloy is activated before immersion in said aqueous
solution.
9 A method according to any one of Claims 5 to 8,
wherein the method comprises dipping the crown region
of the piston into the aqueous solution while keeping
the skirt region of the piston out of the solution.
10 A method of providing at least one surface of a
piston ring groove of a piston made of aluminium or
aluminium alloy with a hard wearing surface having a
hardness in the range 300 to 750 Hv substantially as
hereinbefore described with reference to the
illustrative example.
11 A piston made of aluminium or aluminium alloy having
a hard wearing coating on at least one surface of a
piston ring groove thereof, the coating having a
hardness in the range 300 to 750 Hv comprising cobalt
deposited by electroless plating.
12 A piston according to Claim 11, wherein the coating
contains between 1 and 10% by weight of phosphorus.
13 A piston according to either one of Claims 11 and 12,
wherein the coating is between 6 and 40 microns in
thickness.
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB929224953A GB9224953D0 (en) | 1992-11-28 | 1992-11-28 | Hard wearing surfaces for pistons |
Publications (3)
Publication Number | Publication Date |
---|---|
GB9323865D0 GB9323865D0 (en) | 1994-01-05 |
GB2272959A true GB2272959A (en) | 1994-06-01 |
GB2272959B GB2272959B (en) | 1995-11-22 |
Family
ID=10725824
Family Applications (2)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
GB929224953A Pending GB9224953D0 (en) | 1992-11-28 | 1992-11-28 | Hard wearing surfaces for pistons |
GB9323865A Expired - Fee Related GB2272959B (en) | 1992-11-28 | 1993-11-19 | Hard wearing surfaces for pistons |
Family Applications Before (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
GB929224953A Pending GB9224953D0 (en) | 1992-11-28 | 1992-11-28 | Hard wearing surfaces for pistons |
Country Status (1)
Country | Link |
---|---|
GB (2) | GB9224953D0 (en) |
Cited By (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0690250A1 (en) * | 1994-06-30 | 1996-01-03 | Yamaha Hatsudoki Kabushiki Kaisha | Cylinder unit and method for forming the sliding surfaces thereof |
EP0731300A1 (en) * | 1995-03-09 | 1996-09-11 | Federal-Mogul Burscheid GmbH | Piston ring for combustion engines with a wear-resistant coating |
US6146702A (en) * | 1995-06-06 | 2000-11-14 | Enthone-Omi, Inc. | Electroless nickel cobalt phosphorous composition and plating process |
GB2383833A (en) * | 2001-12-27 | 2003-07-09 | Perkins Engines Co Ltd | Piston with a ceramic reinforced ring groove |
WO2006010450A1 (en) * | 2004-07-26 | 2006-02-02 | Bosch Rexroth Ag | Piston rod comprising a covering layer consisting of a cobalt alloy |
Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPH0286945A (en) * | 1988-09-26 | 1990-03-27 | Riken Corp | Aluminum alloy piston for internal combustion engine |
JPH04119265A (en) * | 1990-05-08 | 1992-04-20 | Riken Corp | Anti-water slide member for internal combustion engine |
JPH05141533A (en) * | 1991-11-20 | 1993-06-08 | Nippon Mekki Kogyo Kk | Piston for internal combustion engine |
-
1992
- 1992-11-28 GB GB929224953A patent/GB9224953D0/en active Pending
-
1993
- 1993-11-19 GB GB9323865A patent/GB2272959B/en not_active Expired - Fee Related
Patent Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPH0286945A (en) * | 1988-09-26 | 1990-03-27 | Riken Corp | Aluminum alloy piston for internal combustion engine |
JPH04119265A (en) * | 1990-05-08 | 1992-04-20 | Riken Corp | Anti-water slide member for internal combustion engine |
JPH05141533A (en) * | 1991-11-20 | 1993-06-08 | Nippon Mekki Kogyo Kk | Piston for internal combustion engine |
Non-Patent Citations (3)
Title |
---|
WPI Abstract Accession No 90-137173/18 & JP 02 086945 A * |
WPI Abstract Accession No 92-187770/23 & JP 04 119265 A * |
WPI Abstract Accession No. 93-217443/27 & JP 05 141533 A * |
Cited By (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0690250A1 (en) * | 1994-06-30 | 1996-01-03 | Yamaha Hatsudoki Kabushiki Kaisha | Cylinder unit and method for forming the sliding surfaces thereof |
US5549086A (en) * | 1994-06-30 | 1996-08-27 | Yamaha Hatsudoki Kabushiki Kaisha | Sliding contact-making structures in internal combustion engine |
EP0731300A1 (en) * | 1995-03-09 | 1996-09-11 | Federal-Mogul Burscheid GmbH | Piston ring for combustion engines with a wear-resistant coating |
US6146702A (en) * | 1995-06-06 | 2000-11-14 | Enthone-Omi, Inc. | Electroless nickel cobalt phosphorous composition and plating process |
GB2383833A (en) * | 2001-12-27 | 2003-07-09 | Perkins Engines Co Ltd | Piston with a ceramic reinforced ring groove |
WO2006010450A1 (en) * | 2004-07-26 | 2006-02-02 | Bosch Rexroth Ag | Piston rod comprising a covering layer consisting of a cobalt alloy |
Also Published As
Publication number | Publication date |
---|---|
GB9224953D0 (en) | 1993-01-20 |
GB9323865D0 (en) | 1994-01-05 |
GB2272959B (en) | 1995-11-22 |
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Legal Events
Date | Code | Title | Description |
---|---|---|---|
PCNP | Patent ceased through non-payment of renewal fee |