U.S. patent application number 12/444046 was filed with the patent office on 2010-02-04 for electroforming method and part or layer obtained via the method.
This patent application is currently assigned to The Swatch Group Research and Development Ltd.. Invention is credited to Joachim Grupp.
Application Number | 20100024930 12/444046 |
Document ID | / |
Family ID | 38799403 |
Filed Date | 2010-02-04 |
United States Patent
Application |
20100024930 |
Kind Code |
A1 |
Grupp; Joachim |
February 4, 2010 |
ELECTROFORMING METHOD AND PART OR LAYER OBTAINED VIA THE METHOD
Abstract
The invention concerns an electroformed gold alloy part,
characterized in that the gold alloy is made up of 88 to 94% by
weight of gold, x % by weight of copper and/or silver, and 2x % by
weight of zinc, x being comprised between 2 and 4.
Inventors: |
Grupp; Joachim; (Enges,
CH) |
Correspondence
Address: |
SUGHRUE MION, PLLC
2100 PENNSYLVANIA AVENUE, N.W., SUITE 800
WASHINGTON
DC
20037
US
|
Assignee: |
The Swatch Group Research and
Development Ltd.
Marin
CH
|
Family ID: |
38799403 |
Appl. No.: |
12/444046 |
Filed: |
October 3, 2007 |
PCT Filed: |
October 3, 2007 |
PCT NO: |
PCT/EP07/60506 |
371 Date: |
April 2, 2009 |
Current U.S.
Class: |
148/678 ; 205/50;
205/67 |
Current CPC
Class: |
C22C 5/02 20130101; C25D
5/18 20130101; C25D 3/62 20130101; C25D 5/50 20130101 |
Class at
Publication: |
148/678 ; 205/67;
205/50 |
International
Class: |
C22C 5/02 20060101
C22C005/02; C25D 1/00 20060101 C25D001/00; C22F 1/14 20060101
C22F001/14 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 3, 2006 |
CH |
1583/06 |
Claims
1-17. (canceled)
18. A method of electroforming a layer of a gold alloy, consisting
in: dipping a metal substrate into an alkaline electrolytic bath
containing an anode, said bath containing at least mainly gold
salts, in the form of potassium gold cyanide, copper salts in the
form of copper cyanide, zinc salts in the form of zinc oxide,
sodium cyanide, sodium hydroxide, ethylenediamino tetra-acetic acid
and a surfactant, said substrate forming a cathode, electroforming
said layer by creating a voltage between the anode and the cathode
to deposit metallic ions on the surface of the substrate,
interrupting the voltage once the desired thickness of the
electroplated layer is obtained in order to generate a layer
containing 88 to 94% by weight of gold.
19. The method according to claim 18 wherein the bath contains 7 to
15 g.l.sup.-1 gold in the form of potassium gold cyanide.
20. The method according to claim 18 wherein the bath contains 1.5
to 5 g.l.sup.-1 zinc in the form of zinc oxide.
21. The method according to claim 18, wherein the bath contains 1.5
to 3 g.l.sup.-1 copper in the form of copper cyanide.
22. The method according to claim 18, wherein the copper in the
form of copper cyanide of the bath is replaced by silver in the
form of silver oxide.
23. The method according to claim 18, wherein the voltage is varied
during the step of electroforming said layer in order to obtain the
gold deposition in the phase .alpha.
24. The method according to claim 23, wherein the voltage is
decreased in the final phase of the electroforming step to increase
the concentration of gold in the superficial zone of the deposited
layer.
25. The method according to claim 18, wherein the electroforming
step is followed by a thermal anneal process, the temperature of
which is comprised between 300.degree. and 700.degree. C. for a
duration of at least 30 minutes.
26. The method according to claim 25, wherein the thermal anneal
process temperature does not exceed the liquefaction temperature of
said gold alloy in order to avoid a gold deposition in several
phases.
27. The method according to claim 25, wherein the thermal anneal
step is followed by a rapid cooling.
28. The method according to claim 27, wherein the cooling step is
made in a reducing atmosphere in order to reduce the zinc
oxide.
29. The method according to claim 18, wherein the surfactant is a
butyl or nonyl phenolpolyglycol phosphatide ester.
30. The method according to claim 18, wherein the electroforming is
performed at a temperature of between 40.degree. and 80.degree. C.
and preferably between 60 and 75.degree. C.
31. A electroformed part made of gold alloy obtained with the
method according to claim 18, wherein the gold alloy is made up of
88 to 94% by weight of gold, x % by weight of copper and/or silver,
and 2x % by weight of zinc, x being comprised between 2 and 4.
32. The electroformed part according to claim 31, wherein the alloy
is made up of 88% by weight of gold, 8% by weight of zinc and 4% by
weight of copper.
33. The electroformed part according to claim 31, wherein the alloy
layer has a thickness of several hundreds of microns.
34. The electroformed part according to claim 31, wherein the gold
in said alloy is essentially formed of phase .alpha. gold.
Description
[0001] The present invention concerns an electroforming method for
making parts or layers from a gold-based alloy containing zinc,
copper and/or silver, and parts or layers obtained via this method.
More specifically, the invention concerns a method of this type for
depositing thick layers of said alloy, typically of the order of
300 microns, on substrates.
[0002] Methods are known for electroplating a gold alloy by
electrolysis in an alkaline galvanic bath containing cadmium, in
addition to gold and copper. As cadmium is a toxic metal, numerous
laws now prohibit the use of cadmium.
[0003] In order to overcome this problem, CH Patent No. 680 927 has
already proposed replacing cadmium with zinc in the conventional
gold alloy (Au, Cu, Cd) electrolytic deposition method.
[0004] However, this method only discloses the deposition of gold,
zinc and copper alloy layers of the order of 10 microns. Moreover,
this document does not give any precise information as to the
composition of the final alloy deposited.
[0005] It is thus a main object of the present invention to provide
a method of electroforming a gold, zinc and copper based alloy part
or layer that is free of cadmium, with a thickness of several
hundred microns.
[0006] It is also an object of the present invention to provide a
method of this type that makes layers of this kind with improved
hardness while maintaining a good level of ductility.
[0007] The invention therefore concerns a method of electroforming
a layer of a gold alloy comprising 88 to 94% by weight of gold, x %
by weight of copper and/or silver, and 2x % by weight of zinc, x
being comprised between 2 and 4, consisting in: [0008] dipping a
metal substrate in an alkaline electrolytic bath containing an
anode, said bath containing at least gold salts in the form of
potassium gold cyanide, copper salts in the form of copper cyanide
and/or silver salts in the form of silver oxide, zinc salts in the
form of zinc oxide, sodium cyanide, sodium hydroxide, acid, for
example ethylene diaminotetra-acetic acid (EDTA) and a surfactant,
said substrate forming a cathode, [0009] electroforming said layer
by creating a voltage between the anode and the cathode to deposit
metallic ions on the surface of the substrate, [0010] interrupting
the voltage once the desired thickness of the electroplated layer
is reached.
[0011] Preferably, the voltage is varied during the step of
electroforming said layer, which produces non-homogenous phase
.alpha. gold crystallisation in the layer at the moment of
deposition. This lack of homogeneity reduces the surfaces defects
in the deposited layer by a crystalline superstructure.
[0012] According to a preferred embodiment of the method of the
invention, the voltage between the anode and cathode is reduced in
the final phase of the electroforming step in order to increase the
concentration of gold in the superficial zone of the deposited
layer and thus reinforce the golden colour of the deposited
layer.
[0013] According to another advantageous aspect of the method of
the invention, the electroforming step is followed by a thermal
anneal process at between 300.degree. and 700.degree. C. for at
least 30 minutes and rapid quenching.
[0014] It will be noted in this regard that the "liquidus"
temperature curve of the Au Zn phase diagram, must not, in any
circumstances, be exceeded for the alloy concerned, since during
eutectic solidification, from the liquid phase, this would cause
solidification in two phases .alpha.,.beta.', which would result in
a marked degradation in mechanical properties after cooling. During
this treatment, the crystalline structure of the layer is partially
homogenised and then solidified in this forming process by rapid
hardening, which prevents intermediate .alpha.1 or .alpha.2
crystalline phases forming for the alloy concerned.
[0015] The invention also concerns an electroformed gold alloy
part, characterized in that the gold alloy comprises from 88 to 94%
by weight of gold, x % by weight of copper and/or silver, and 2x %
by weight of zinc, x being comprised between 2 and 4.
[0016] According to a preferred embodiment of the invention, the
alloy comprises 88% by weight of gold, 8% by weight of zinc and 4%
by weight of copper.
[0017] Electroforming is performed at a temperature of between
40.degree. C. and 80.degree. C.
[0018] According to an advantageous embodiment, the surfactant used
is a phosphatic ester of a polyglycol alkyl alcohol.
[0019] According to the method of the invention, electrolysis is
performed in an alkaline galvanic bath with a pH of between 8 and
10, containing approximately 7 to 15 g.l.sup.-1 of gold in the form
of potassium gold cyanide, approximately 1.5 to 5 g.l.sup.-1 of
zinc in the form of zinc oxide, approximately 1.5 to 3 g.l.sup.-1
of copper or silver in the form of copper cyanide or silver oxide,
sodium cyanide, sodium hydroxide, ethylenediamino tetra-acetic acid
and its potassium salt and a surfactant.
[0020] This electrolysis step is followed by a heat treatment at at
least 300.degree. C. for at least 30 minutes. This heat treatment
is preferably carried out in a reducing atmosphere to reduce the
zinc oxide.
[0021] Preferably, the galvanic bath further contains a brightener.
The brightener is preferably a potassium antimony tartrate combined
with potassium hypophosphite or a potassium selenocyanate.
[0022] The surfactant is preferably a butyl or nonyl phenol
polyglycol phosphatide ester.
[0023] The electrolysis is preferably carried out at a temperature
of between 60 and 75.degree. C. in a galvanic bath whose pH is
between 8 and 10.
[0024] The electrolysis can be achieved with a current density
typically of the order of 1.0 A.dm.sup.-2.
[0025] The electrolysis is followed by a heat treatment carried out
at a temperature higher than 300.degree. C. for a time of typically
between 30 minutes and 1 hour. This heat treatment includes rapid
air cooling, which can be obtained, for example, in a band furnace.
The heat treatment is performed under a reducing atmosphere.
[0026] We will now describe an example of the electrolytic
deposition according to this embodiment of the invention and the
method of preparation for the same.
[0027] In this deposition example, there is an 18 carat gold alloy,
free of toxic metals or metalloids, in particular free of cadmium,
with a pale yellow colour 2N, with a hardness of between 200 and
300 HV 0.005, ductile in particular for thicknesses of between 40
and 350 microns, with excellent brilliance and with a very high
level of resistance to wear and tarnishing.
[0028] This deposition is obtained by electrolysis in an
electrolytic bath followed by a heat treatment at 300.degree. C.
for 30 minutes under a reducing atmosphere.
[0029] The electrolysis is performed in an electrolytic bath
containing the following compounds:
EXAMPLE
[0030] Au in the form of KAu(CN).sub.2: 11 g.l.sup.-1
[0031] Cu in the form of CUCN: 2.5 g.l.sup.-1
[0032] Zn in the form of ZnO: 2.5 g.l.sup.-1
[0033] NaCN: 20 g.l.sup.-1
[0034] NaOH: 5.5 g.l.sup.-1
[0035] KHCO.sub.3: 5 g.l.sup.-1
[0036] K4[EDTA]: 5 g.l.sup.-1
[0037] H.sub.4[EDTA]: 5 g.l.sup.-1
[0038] PH: 8
[0039] Temperature: 70.degree. C.
[0040] Current density: 1 A.dm.sup.-2
[0041] Wetting agent: 0.2 mg.l.sup.-1 phosphatide butyl phenol
polyglycol ester
[0042] Potassium selenocyanate: 10 mg.l.sup.-1
[0043] EDTA=ethylene diaminotetra-acetic acid
[0044] In this example, the electrolytic bath, contained in a
polypropylene or PVC container with thermal insulation, has a pH of
between 8 and 10 and is at a temperature of 70.degree. C. The bath
is heated using quartz, PTFE, porcelain or stabilised stainless
steel immersion heaters. The bath has a density of between 16 and
30 g.cm.sup.-3 at 20.degree. C. Good cathode rod movement and
electrolyte flow must be maintained. The anodes are made of
platinum plated titanium or stainless steel.
[0045] The electrolysis is performed with a current of between 1
and 2 A.dm.sup.-2. These conditions provide cathode efficiency of
100 mg.A.min.sup.-1.cm.sup.-2 with a speed of 0.5
micron.min.sup.-1.
[0046] Of course the present invention is not limited to the
example illustrated but can be subject to various variants and
alterations which will be clear to those skilled in the art. In
particular, the bath can contain traces of silver and the following
metals: In, Cd, Zr, Se, Te, Sb, Sn, Ga, As, Sr, Be, Bi.
[0047] Moreover, the wetting agent may be of any type that can wet
in an alkaline cyanided medium.
* * * * *