DE2237834A1 - ITEM MADE OF A METALLIC BASE BODY WITH A METALLIC COATING - Google Patents

Description

Object made from a metallic base body with a metallic coating

The invention relates to an object made of a metallic material Base body with a metallic coating.

It is known to provide metallic objects with a coating to improve their surface properties, which can be done, for example, by electroplating.

It has now been found that the metallic coatings in the case of the known objects do not fully meet the demands placed on them.

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The invention was therefore based on the object of a new object To propose a metallic base body with an improved metallic coating.

This object is achieved by an object made of a metallic base body with a metallic coating, which thereby is characterized in that the metallic coating has a strip structure and is relatively hard.

A method for honing and electroplating is from DOS 2 Öl7 18o known, in which the metallic surface of a workpiece is first honed electrochemically, with a current flows in one direction, in which an electroplating and honing cycle is then carried out in order to at the same time Honing to deposit metal on the surface of the workpiece or to plate metal on this surface, the Current flows in the opposite direction, and in which finally the current flow is interrupted and another Honing process is carried out in order to bring about the desired surface finish by mechanical removal of material.

From DOS 2 o29 646 is a similar electroplating and Honing method known in which the metallic surface of a workpiece is first cleaned by honing, in which the honing tool is then used as an electrode to perform an electroplating and honing cycle during which metal on the surface is honed with simultaneous honing of the workpiece is deposited, and at which the current

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flow is then interrupted to be used in a further honing process the desired surface finish through mechanical material removal to create.

With these known electroplating and honing processes the metallic surface of the base body is cleaned either by purely mechanical or electrochemical honing, and electroplating is then carried out with high current densities and a correspondingly high metal deposition rate and finally, an accurate surface treatment by honing. Etching can thus be carried out in the known methods the surface to be plated in an acid and / or masking of adjacent surface parts is not necessary. The metal namely, is only deposited on the surface parts that are closely adjacent to the electrode, which in this case simultaneously the honing tool forms.

It is known that most of the coatings applied using common electrolytic processes are deposited, have properties similar to those of a forged metal of the same composition. Not alloyed, by electroplating deposited layers are usually under tensile stress and would contract if they would not be prevented from doing so by the basic body that supports them. The crystal growth occurs perpendicular to the surface of the Basic body, what with the help of the usual, metallographic Test method can be demonstrated. Changes in hardness, internal stresses and the crystalline structure can

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can be achieved by using additives to the electrolytes, through which one or more alloy components are introduced into the coating. These alloy components can be metallic or non-metallic atoms, such as sulfur and phosphorus.

It has now been found that using the electroplating and honing processes described above, metallic coatings can be produced that are free of alloy components, such as phosphorus or sulfur, and which are due to internal compressive stresses, one above that normally achieved Hardness is characterized by hardness and a striped structure of its crystalline structure. The pillar structure of the in usual Layers created by electroplating can be converted into a strip structure by using additives, which lead to materials such as sulfur or phosphorus being deposited at the same time as the metal. One Such a transformation of the microstructure is desirable, since a layer with a strip structure is stronger and harder and less, has internal tensile stresses. The presence of low, internal tensile stresses and preferably even the presence of Internal compressive stress is desirable because durability is higher when the surface of a structure is under internal compressive stress stands. On the other hand, the alloying of sulfur has the disadvantage that the elongation or the The ductility of the metal is reduced, the sensitivity to corrosion is increased and the coating becomes hot-brittle becomes (i.e. very brittle when warm). In addition, is

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the influence of these alloy components on the internal stresses too low to overcome the normally present "internal" tensile stresses or even the desired high ones Generate compressive stresses in the coating.

It has now been shown, however, that with the known plating and honing processes allow the benefits attainable by adding sulfur to be achieved without sacrificing those with sulfur additives associated disadvantages would occur. It has also been shown that with this method in the coating allow higher compressive stresses to build up, which are particularly useful for Increases in shelf life are desirable.

A typical article of the present invention is from a metallic base body and a metallic coating applied to it, which has a strip structure, which is generated in it by mechanical material abrasion during its deposition; also has the coating a significantly greater hardness than a coating deposited from the same using conventional methods Material.

In a further development of the invention, it has proven particularly useful if the base body of the object is made of cast iron, steel, Aluminum, titanium, stainless steel, bronze or a zinc-based injection molding material.

It has also proven useful if the coating is the predominant

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contains copper, nickel, cobalt, chromium, bronze, tin, iron, silver or cadmium. Preferably the coating is about 12.7 μ to 254 μ thick and essentially free of sulfur. Preferably the sulfur content is the coating below about o, ol%.

If the coating contains predominantly nickel or cobalt, its Knoop hardness is usually at least about 500; if, on the other hand, it contains predominantly copper, its Knoop hardness lies usually at least about 2oo *, and if it contains predominantly chromium, its Knoop hardness is usually around at least about 1,3oo.

The internal stress of the coating is usually one Compressive stress that occurs when the load is predominantly made of copper

2 layers between about 562 and 633 kg / cm, the coatings consisting predominantly of nickel between et-

2
wa 2.46ο and 3.16o kg / cm and the coatings consisting predominantly of cobalt between about 2.39o and

2
3.73o kg / cm.

After the deposition, the surface of the coating typically has an accuracy that is within a tolerance range of about 5 μ compared to a given shape.

Further details and advantages of the invention are provided below explained in more detail using a drawing. In the drawing show:

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1 shows a photomicrograph of an etched cross section through an object with a base body made of cast iron,
which has a copper coating deposited in a conventional electroplating process, magnified 2oo times,

FIG. 2 shows a microphotograph of a FIG. 1 corresponding to

corresponding article according to the invention, but with the copper coating on the existing cast iron Base body was produced by honing and plating,

3 shows a photomicrograph of an etched cross-section through an object with a 4.13o steel base body,
which has a nickel coating deposited in a conventional electroplating process, magnified 2oo times,

1+ shows a microphotograph corresponding to FIG. 3 of an object according to the invention, in which the nickel coating on the 4.13o steel base body is through
Honing and plating was produced as well

Fig. 5. · '

to 8 are schematic representations of the microphotographs according to FIGS. 1 to H.

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Copper, nickel and cobalt coatings were made using conventional electroplating techniques for comparison purposes With the objects according to the invention applied to cylindrical base bodies, and selected physical Properties of the coatings and the objects evaluated.

For plating the inner surfaces of cylindrical parts, they have been preferred Electroplating solution compositions and preferred manufacturing methods selected. In particular, were Manufacturing processes are selected that use anodes that are insoluble in all plating solutions. Unsolvable Anodes for generating a uniform current distribution on the inner surface of a bore are known in the art Manufacturing process already used, at the same time external Systems for regenerating and maintaining the composition of the solution are provided. With the sulfate solutions, the compositions of which are given in Table A in detail, anodes made of a lead alloy were used, which contained 7% tin.

The following methods were used for cleaning and surface activation used: 1. vapor degreasing in trichlorethylene, 2. electrolytic cleaning in a hot, alkaline cleaning solution and 3. Immersion in 3N hydrochloric acid to neutralize the alkali and remove surface oxides. Cast iron bodies were first plated with a copper cyanide precipitate before the copper plating in acidic solution.

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solution took place. Objects with a basic body from 4.13ο- and 5,615 alloy steel were initially deposited with a nickel deposit provided before either nickel or cobalt has been plated. The composition of the solution used to generate the nickel deposit is given in Table A.

Measurement of. physical properties

Hardness:

Parts of the cylindrical test specimens were assembled for metallographic polishing and examination. The hardnesses determined are given in Table C. The print marks for determining the hardness were measured with a Tukon tester using a Knoop stamp for measuring the hardness numbers generated. That Tukon tester was used because it is easy to measure thin coatings.

Structure:

The cut and polished specimens were used common metallographic process to determine the structure of the coating. Figures 1 to 4 show the Structures of typical coatings. In detail, FIGS. 1 and 3 show the typical column structure of FIG Electroplating applied coatings, while FIGS. 2 and 4 show the strip structure, which for the through Honing and plating produced coatings according to the invention Objects is typical.

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Internal tensions:

Have metallic layers deposited by electroplating often internal stresses, either compressive stresses or tensile stresses. These tensions call forces on the Interface between the deposited layer and the base body which can affect the adhesion, strength and ductility of the coating. The internal tensions were determined on the basis of the change in diameter of the cylindrical test specimen that occurred when it was parallel to its axis were cut. The changes in diameter are recorded in Table C. The data given there became the internal Stresses determined according to the following formula:

Et ²

S.

whereby:

E = modulus of elasticity of the base body in psi (1 psi = 0.07 kg / cm ² )

S = stress in psi

t = thickness of the substrate in inches

d = thickness of precipitation in inches

/ \ p = change in cylinder diameter.

This formula was proposed by A. Brenner and S. Senderoff in the article "A Spiral Contractometer for Measuring Stress in Electrodeposits" published in J. Research NBS, Ho, pages 89 to (19 49).

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The voltage values calculated according to this formula for the various Test specimens are recorded in Table D. The values given in Table D are approximate, as some of the Parameters in the above equation could only be estimated. The change in the diameter of the cylindrical test specimen was calculated by subtracting the change for an uncoated cylinder from the measured change for a coated cylinder became. The modulus of elasticity for the base body made of steel and cast iron was 3o, ooo, ooo psi and 15, ooo, ooo psi accepted. The ratio of the thickness of the cylinder wall to the thickness of the coating was such that the deflections were small and were practically impossible to measure accurately. The measurements of the thickness of the cylinder wall and the coating were also errors subject.

. Water content

Parts of the test specimens according to the invention and the test specimens produced in the usual manner were with respect to one remaining Hydrogen content examined using vacuum melt flow analysis.

The test results recorded in Table E show for all test specimens have a low hydrogen content except for the copper-coated base body in which the coating done by honing and plating.

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Sulfur analysis

Since the coatings produced by honing and plating showed a stripe structure, which is the case with the usual electroplating processes was a sequence of sulfides which were introduced into the electroplating solution by means of an organic additive the various coatings were analyzed to determine their sulfur content by electroplating applied layers which have a sulfur content of more than o, ol%. The sulfur analysis leads to the following Results:

Solution for honing and plating Sulfur content of the coating

tion in% by weight

Copper bath with voltage reducer 0.016

Nickel sulfamate bath with stress reducer 0.030

Nickel sulphate bath without stress reducer 0.00 «4

Cobalt sulfamate bath with voltage reducer 0.029

Cobalt sulfate bath 0.007

discussion of the results

Hardness:

The coatings made by honing and plating

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were much harder than those produced by conventional electroplating processes produced coatings, as is evident from Table F.

The higher hardness numbers of those made by honing and plating Precipitations are produced during mechanical processing attributed to the deposition. The production of hard coatings without the use of special additives in the electrolyte leads to advantages where good abrasion resistance is desired. Coatings produced by conventional electroplating can be made harder by adding suitable additives to the electrolyte. Controlling the concentration of this However, additives have an additional cost. The application of coatings by honing and plating brings about thus an advantage with itself because hard coatings are produced without the need for additives.

Structure and sulfur content:

Since the strip structure is not possible with the usual electroplating processes can be produced if no sulfur-containing additives are added to the plating solution, the strip structure must, as it is produced by honing and plating can be regarded as unique.

Internal '' stresses in copper, nickel, cobalt and chromium:

The copper, nickel and Cobalt coatings unexpectedly showed internal pressure

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tensions. They would expand if they weren't prevented from doing so by the basic body. Stand in contrast to this most coatings produced by conventional electroplating under internal tensile stress, unless specified Additive and / or processing methods are used. The compressive stresses are probably a consequence of the mechanical ones Disturbance of the crystal structure during cladding due to the simultaneous honing. The same process is obviously also for the high hardness, for the strip structure and for the lower than expected shear strength. High internal compressive stresses are particularly desirable when the inside of bores is coated.

As already mentioned above, FIGS. 5 to 8 show schematic representations of the microphotographs according to FIGS. 1 to U, wherein FIG. 5 corresponds to FIG. 1, FIG. 6 corresponds to FIG. 2, FIG. 7 corresponds to FIG. 3 and FIG. 8 corresponds to FIG. In Figures 5 and FIG. 7, the column structure of the coating is indicated by vertical hatching, while the strip structure of the invention Objects in Fig. 6 and 8 is indicated by horizontal hatching. Furthermore, in FIGS to 8 the base body is designated by 1. That part of the coating that has a column structure or a strip structure is provided with the reference number 2. The surface layers machined by honing are finally given the reference number 3 designated.

Tables A to F follow:

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. .Table A

Solution compositions and conditions for the Electroplating

Electroplating with copper

Composition of the solution:

Copper sulfate CCuSO ₁₁ 5H ₂ O)

Sulfuric acid Plating conditions:

temperature

Move

Current density

duration

21o g / l ο, 67 A / cm 52 g / i o, 7 min / u 35 ° C air approx. approx.

Electroplating with nickel

Composition of the solution:

Nickel sulfate (NiSO ₁₁

Boric Acid Plating Conditions:

temperature

Move

Current density

duration

6H ₂ O)

33o g / i A / cm ² 3o g / i min / µ 54, 4 ° C air approx. o, 67 approx. o, 79

'Electroplating with' cobalt

Composition of the solution: cobalt sulfate boric acid

7H ₂ O) 33o g / l 3o g / l

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Electroplating with Cobalt (continued)

Plating conditions:

Temperature 54, U C

Movement air

Current density approx. 0.67 A / cm

Duration approx. 79 min / μ

Ni cke lriie the s ch lay

Composition of the solution:

Nickel sulfate (NiSO ₁₊ 6H ₂ O)

Sulfuric acid plating conditions:

temperature

duration

Current density

24o g / l 5o g / i 35 ° C 5 min approx. 1.68 A / cm ²

Honing and plating process

The conditions prevailing in honing and plating the articles of the invention are summarized in Table B.

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Table B Conditions for honing and plating the cylindrical specimens

co σ co co ο

Test specimen metal Honing Conditions: CD) Cf) Pressure2
kg / cm Time
lake solution Rejection conditions Ampdre Pressure"
kg / cm. *
• Time
min Deposition copper No. 413o Grinding
middle CD) Cf) 3.52 15th 5Ce) Temß.
. caA ο, 55 0.35 3.5. Thick metal
P. 17th 413o SteelC d) CD) Cf) 3.52 15th 5Ce) 27.8 ο, 67 o, 35 3.5 63, 5o If
\ 16 413o Il CD) 3.52 15th 5Ce) 27.8 ο, 55 o, 35 3.5 45.72 2 8 413o Il CD) 3.52 15th 5Ce) 27.8 ο, 55 o, 35 12th 48.26 23 413 ο Il CD) 3.52 15th 5Ce) 27.8 ο, 55 o, 35 12th 19o, o5 It 22nd 413o ti CD) 3.52 15th 5Ce) 27.8 ο, 55 o, 35 15th 228.6o ti 33 413o It CD) 3.52 15th 5Ce) 27.8 ο, 55 o, 35 15th 228.6o Il 39 CI It CD) 3.52 15th 5Ce) 32.2 ο, 55 o, 35 15th .241.3o » 18th CI StahlC f) 3.52 15th 5Ce) 37.8 o, 55 o, 35 3.5 223.5 If 19th CI It 3.52 15th 5Ce) 37.8 o, 55 o, 35 - 3.5 63.5o Nickel. 2 ο 413o Il 3.52 15th 2Cg) 37.8 o, 22 o, 7o 7, ο 63.5o "N> 59 413o 3.52 15th 2Cg) 63, o o, 22 o, 7o 7, ο 55.88 If * A * 63 413o 3.52 15th 2Cg) 64.0 o, 22 o, 7o 15th 55.88 Il OO
c. k 71 CI 3.52 15th 2Cg) 6o, o o, 22 o, 7o 15th 121.9o 26th 62.5o lol, 6o

Table B (continued)

Test specimen honing conditions; Abs marriage conditions: No. Metal grinding pressure »time solution temp. Ampere pressure« time mean kg / cm see approx. C kg / cm min

Deposition thick metal

GJ
O
CO

24
21
67
36
77
39
22nd
17th
26th
22nd
4o
73
64
12th
18th
25th

CI

CI

413o

413o

413o

CI

CI

CI

5616

5616

5616

413 ο

413o

413o

5616

5616

Cf) Cf)

Steel Cd) Cd) (d) Cd) (d) CD)

SteelC i) Ci) Ci) Ci) Ci) Ci)

¹¹ Ci) Ci)

3.52
3.52
3.52
3.52
3.52
3.52
3.52
3.52
2.81
2.81
2.81
3.52
3.52
3.52
3.87
3.87

15th

1.5
15th

15th
15th
15th
15th
15th
Io
Io
Io
Io
Io
Io
Io
Io

2Cg)
2 (g)

Ch)

Ch)

Ch)

Ch)

Ch) ·

Ch)
2
2
2

Cj)

Cj)

Cj)

Cj)

Cj)

64, ο 65.6 65.6 65.6 65.6 64, ο 65.6 65.6 65.6 65.6 63, ο 65.6 65.6 65.6 6o, o 6o, o

o, 22 o, 22 o, 93 o,? 3 o, 9 3 o, 47 o, 47 o, 47 o, 47 o, 47 .47 o, 7o o, 7o o, 7o o, 47 o, 47

o, 7o o, 7o o, 35 o, 35 o, 35 o, 7o o, 7o o, 7o o, 7o o, 7o o, 7o o, 7o o, 7o o, 7o o, 56 o, 56

7, ο 7, ο 2, ο 2, ο

5, o 4, o 4, ο 8, ο 4, ο 4, ο

8, ο 2, ο 2, ο

6, o 2.0 3, o

58.42 nickel

5 8.42 "

76.2o cobalt

76.2o "172.7o"

83.82 "to

76.2o "139.7o"

71.12 nickel

73.66 "139.7o"

5 8.42 "

5o, 8o "152.4o"

38, Io "

58.42 "

Table B (continued

Test specimen honing conditions, deposition conditions, deposition

JNr. Metal grinding
middle . SteelCi)
(f) Pressure ₂
kg / cm. Time
lake solution Temp.
approx ⁰ C Amp tire Pressure-
kg / cm Time
min. . . Thick metal
μ 35
38 5616
5616 (f) 3.87
2.81 Io
Io (J)
(k) 65.6
68, ο ο, 48
ο, 23 ο, 56
ο, 7ο 8, ο
6, ο 139.7 nickel
6ο, 96 cobalt CO
O 39 5616 Cf) 2.81 Io Ck) 65.6 ο, 23 ο, 7ο 4, ο 45.72 " CD
CO. 29 5616 (i) 2.81 Io Ck-) 65.6 ο, 23 ο, 7ο 12, ο ' Ιοί, 6ο " O 3o CI Ci) 1.76 Io (j) 65.6 ο, 47 ο, 35 2, ο 48.26 nickel 28 CI (i) 3.87 Io Cj) 65.6 ο, 47 ο, 35 2, ο 38.1ο " O
(O 38 CI 3.87 Io (j) 65.6 ο, 47 ο, 35 7, ο 139.7ο " U) Footnotes for table B

Ca) Honing pressure before the start of deposition. Cb) Honing pressure during deposition Cc) C-IZO-IBF χ 2 honing stones Cd) copper sulphate with complexing agent Ce) BC-220-H4-VEC stone

Cf) nickel sulfamate solution

Cg) Solution number unknown

Ch) C-220-J4-VEC-Honing Stone

Ci) nickel sulfate boric acid solution

Cj) cobalt sulfate solution

Table C.

Hardness of the deposited metal and change in diameter

of the test body

Test specimen - closed metal Base body thickness And.d. Diameter flat.
Body. JL) Xi f. Knoop hardness ^R B O NJ __ reason
body +114 + 76.2 234 ^R c 97 I. > 37834 2o 37B copper (c) Cast iron 63.5 + 38.1 + 2o3 + 122 234 - 97 39 36B copper (c) 413o steel 241.3 + 81.3 + 81.3 O Io5 - 48 44 copper (d) 413o steel 5o, 8 + 81.3 + 63.5 + 25.4 76 - 15th 33 - copper (d) Cast iron 5o, 8 + 38.1 +197 + 114 553 - - 64 - nickel (e) 413o steel 5o, 8 + 81.3 + 244 +163 674 52 - 59 3 7A nickel (f) 413o steel 55.9 + 81.3 + 535 + 5o4 642 57 - 26th - nickel (f) Cast iron lol, 6 + 38.1 - 38.1 - 76.2 274 56 - 11 - nickel (G) Cast iron 53.34 + 38.1 + 262 + 22.4 528 24 - 3o 36A nickel (e) Cast iron 48, 26 + 38.1 + 53.4 + 91.4 534 51 - 18th - nickel (e) 5616 steel 38.1 -38.1 + 5o, 8 -3o, 5 198 51 89 4o nickel (G) 413o steel 5o, 9 + 81.3 + 445 + 4o7 6o4 - - 17th cobalt (f) Cast iron 83.82 + 38.1 + 96.5 + 135 617 55 38 cobalt (H) 5616 steel 6o, 96 -38.1 54

Table C (continued)

Test body cut off metal

Base body thickness changes d. ' Diam
μ baseplate. Diff.
body . .Body

Knoop

hardness

1 + 6

67

97

lol

UoA

Cobalt (i)
Cobalt CF)
Chrome (j)
Chrome (j)

413o steel 413o steel 413o steel 413o steel 76.2 +81.3
22.61 +81.3
23.37 +81.3

+345 +264
+45.8 -35.6
+33 -48.3

313 - -

546 52 -

14 8o - -

136 3 - -

(a) Change in cylinder diameter after cutting one of the sections.

<b) The Knoop numbers were measured. The Rockwell hardness (R ₀ , R _n ) was obtained from conversion tables

derived. It

a load of loo g was used in all cases, except for chrome, where a solid of 50 g was used.

(c) Honing and plating in a copper sulphate bath, which is an alkaline, contains complexing agent,

(d) Conventional electroplating in one. sulfuric acid copper sulfate bath.

(e) Honing and plating in a sulphate bath.

(f) Honing and plating in a sulfamate bath with a voltage reducer.

(g) Conventional electroplating in a nickel sulfate bath.

Ch) Honing and plating in a cobalt suIfate bath.

(i) Conventional electroplating in a cobalt sulfate bath.

(j) honing and plating in a chromium solution,

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Table D.

Approximate stresses in coatings produced by honing and plating (a)

Metal
layering Base body Honing and plating
bath Tension (b)
(kg / cm ² ) copper 413o steel, alkaline sulfate -633 copper Cast iron alkaline sulfate -562 (c) nickel 413o steel SuIfamat -316ο nickel 5616 steel sulfate -26oo nickel Cast iron Sulfamate -264o Cc) nickel Cast iron sulfate -246o (c) nickel 413o steel sulfate -246o cobalt 413o steel Sulfamate -373o cobalt 5616 steel sulfate -239o chrome 413o steel . unknown + 169o

(a) For comparison: with copper and nickel layers that are electrolytically deposited on such cylinders in the usual way the internal stresses are tensile stresses of approx

267 kg / cm or 633 kg / cm ² to about 773 kg / cm ² .

(b) Compressive stresses are with a negative sign, tensile stresses indicated with a positive sign.

(c) This value is probably so high because The base body and the coating have different expansion coefficients.

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Table E.

Hydrogen content of the clad steel test specimens

Manufacturing coating base body Hydrogen content process (a) (ppm)

Honing and plating

conventional electroplating, honing and plating

Honing and plating

Common Electroplating Common Electroplating Honing and Plating

usual electroplating copper Ul3o steel

copper

nickel

^(b)

Nickel ^(b)

nickel

^(b)

cobalt

"3o stole 2, ο 113. stole 6.2 5616 stole . 2.7 413o stole 1.6 5616 stole 2.6 5616 stole 5.1 U13o stole H, 2

(a) Vacuum Melt Flow Analysis

(b) Honing and plating with sulfate solutions

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Table F.
Summary of typical mechanical properties

Metal Deposition Process Internal Stress Knoop Hardness Number

usual electro
plate 281 train loo copper Honing and Plattie
ren 633 pressure 235 copper usual electro
plate 7o3 train 2oo nickel Honing and Plattie
ren 281o Pressure 65o nickel usual electro
plate li + lo train 3oo cobalt Honing and Plattie
ren 352o pressure 600 cobalt usual electro
plate 352o train 9oo chrome Honing and Plattie
ren 179o train lUoo chrome

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Claims (2)

Claims 1. Object made of a metallic base body with a metallic one Coating, characterized in that the metallic coating has a strip structure and has a relatively great hardness. 2. Object according to claim I _9, characterized in that the base body consists of cast iron, steel, aluminum, titanium, stainless steel, bronze or injection-molded material based on zinc. 3. Object according to claim I _9, characterized in that the coating consists predominantly of copper, nickel, cobalt, chromium, bronze, tin, silver, iron or cadmium. According to claim 1 to 3 _{9 9} characterized in that the coating μ a thickness of about 12.7 μ has ¹ I. Subject to about 25H. 5. The article of claim 1, characterized in that the coating is substantially free of sulfur. 6. The article of claim 5, characterized in that the coating contains less than about ο, oil% sulfur. - 26 - 09807/0934 A 39 579 b _% - - 2% - k-116
31.o7.72 7. Object nachJAnspruch 6, characterized in that the Coating consists predominantly of nickel or cobalt and that its Knoop hardness is at least about 500. 8. The article according to claim 6, characterized in that the coating consists predominantly of copper and that its Knoop hardness is at least about 2oo. 9. The object of claim 6, characterized in that the coating consists predominantly of chromium and that its Knoop hardness is at least about 1,3oo. 10. Object according to one or more of the preceding claims, characterized in that the internal stresses in the coating are compressive stresses. 11. The object of claim Io, characterized in that the internal compressive stresses in coatings that exceed 2 consist mainly of copper, between about 56 and 2 kg / cm 2
about 633 kg / cm, that the internal compressive stresses in coatings that mainly consist of nickel, 2 2 are between about 2.U6o kg / cm and about 3.16o kg / cm, and that the internal compressive stresses in coatings that 2 consist mainly of cobalt, between about 2,390 kg / cm 2
and about 3.7 3o kg / cm. 12. Object according to one or more of the preceding claims, characterized in that the surface of the - 27 - 309807 / 093A A 39 579 b k-146 31.o7.72 layering has tolerances of about 5 μ with respect to a predetermined shape after the deposition. 309 8-0 7/0934