PROCEDE DE VAPORISATION PERMETTANT DE DONNER LA RUGOSITE VOULUE A LA SURFACE D'UNE PIECE A USINER, APPLICATION TIREE DE CE PROCEDE ET SURFACE AINSI OBTENUE

PROCESS FOR THE PRODUCTION OF A SPRAYED SURFACE OF DEFINED ROUGHNESS ON A WORKPIECE AND THE USE OF THE PROCESS AND THE SURFACE PRODUCED THEREBY

Abrégé anglais

ABSTRACT
A process for the production of a sprayed surface of defined
roughness on a workpiece is to be improved and a surface layer with a
clearly defined degree of roughness is to be provided, by a
comparatively simple procedure.
For that purpose, a powder material is sprayed on the surface,
the material comprising a mixture of a matrix on a Ni, Co and/or Fe-base
alloy, and hard materials, as well as a grain-size distribution in
respect of the hard materials with a maximum proportion between 25 and
150 µm, wherein the sprayed unsintered layer has a surface roughness in
the range of Ra 10 to 100 µm of a defined roughness of Ra.x ? 20 µm, and
x is a number of from 10 to 100 µm. The invention also embraces use of
the process for the production of the surface of transport rollers or
gripper fingers for paper or cardboard manufacture.

Revendications

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A process for producing a slip-resistant surface on a
workpiece, comprising: thermally spraying a surface of the
workpiece with a powder mixture comprising: a mixture of a
hard material selected from a carbide, boride, silicide,
nitride, oxide and a mixture thereof on a matrix of an alloy
based on Ni, Co, Fe or a mixture thereof; wherein the grain-
size distribution of said hard material is between 25 to 150
µm, and wherein the sprayed but unsintered surface has a
roughness, Ra, in the range of 10 to 100 µm, with a defined
degree of roughness of Ra.x ? 20 µm, wherein x is in the
range of 10 to 100 µm.
2. The process of claim 1, wherein said hard material is a
boride.
3. The process of claim 1, wherein said hard material is a
silicide.
4. The process of claim 1, wherein said hard material is a
nitride.
5. The process of claim 1, wherein said hard material is a
oxide.
6. The process of claim 1, wherein said hard material is a
carbide.
7. The process of claim 6, wherein the carbide is a
tungsten-based carbide.
8. The process of claim 7, wherein the tungsten-based
carbide is sintered.

9. The process of claim 6, wherein the carbide is a tungsten
carbide-cobalt, with a cobalt content of less than 25%.
10. The process of claim 1, wherein said hard material is
coated, prior to mixing with said matrix, with Ni, Co, Fe or
a mixture thereof.
11. The process of claim 10, wherein the Ni, Co, Fe, or
mixture thereof in the coating is less than 40 weight percent
of said hard material core.
12. The process of claim 11, wherein the Ni, Co, Fe or
mixture thereof in the coating is less than 20 weight
percent.
13. The process of claim 1, wherein the grain-size
distribution is between 37 and 125 µm.
14. The process of claim 13, wherein the grain-size
distribution is between 45 and 105 µm.
15. The process of claim 14, wherein the grain-size
distribution is between 45 and 90 µm.
16. The process of claim 13, wherein the grain-size
distribution is 37 to 75 µm.
17. The process of any one of claims 1 to 16, wherein the
defined degree of roughness is Ra.x ? 10 µm.
18. The process of any one of claims 1 to 16, wherein said
hard material comprises 20 to 80 weight percent of the
mixture.

19. The process of any one of claims 1 to 16, wherein said
hard material comprises 30 to 60 weight percent of the
mixture.
20. The process of any one of claims 1 to 16, wherein said
hard material is produced by spray drying.
21. The process of any one of claims 1 to 16, wherein said
hard material is produced by agglomeration.
22. The process of any one of claims 1 to 16, wherein said
hard material is produced by agglomeration and sintering.
23. The process of any one of claims 1 to 16, wherein said
hard material is produced by melting.
24. The process of any one of claims 1 to 16, wherein said
hard material is produced by crushing and grinding.
25. The process of any one of claims 1 to 16, wherein said
hard material grains are spherical.
26. The process of any one of claims 1 to 16, wherein said
hard material grains are polygonal.
27. The process of any one of claims 1 to 16, wherein said
matrix is a Ni-based alloy.
28. The process of any one of claims 1 to 16, wherein said
matrix is a Ni-Cr-based alloy.
29. The process of any one of claims 1 to 16, wherein said
matrix is a Ni-Cr-Fe-based alloy.
30. The process of any one of claims 1 to 16, wherein said
matrix is a Ni-Cr-B-Si alloy.

31. The process of any one of claims 1 to 16, wherein said
matrix is a Co-based alloy.
32. The process of any one of claims 1 to 16, wherein said
matrix is a Fe-based alloy.
33. The process of any one of claims 1 to 16, wherein the
grain-size distribution of said matrix is between 150 and 5
µm.
34. The process of any one of claims 1 to 16, wherein the
melting point interval of said alloy is 900 to 1,400°C.
35. The process of any one of claims 1 to 16, wherein the
melting point interval of said alloy is 1,000 to 1,300°C.
36. The process of any one of claims 1 to 16, wherein the
melting point interval of said alloy is more than 50°C.
37. The process of any one of claims 1 to 16, wherein the
thermal spraying is effected with an autogenous flame
spraying apparatus.
38. The process of any one of claims 1 to 16, wherein the
thermal spraying is effected by plasma flame spraying.
39. The process of any one of claims 1 to 16, wherein the
melting point of said hard material is at least 1,200°C.
40. The process of any one of claims 1 to 16, wherein the
slip resistant surface is produced on a surface of a
transport roller for paper manufacture.
41. The process of any one of claims 1 to 16, wherein the
slip resistant surface is produced on a gripper finger for
transporting a sheet of paper or cardboard.

Description

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The invention relates to a process for the production of a
sprayed surface of defined roughne~s on a workpiece and the
use of the process and the surface produced thereby.
Thermally sprayed iayers, after the spraying operation, have
a rough surface whose degree of roughness lies within a
comparatively wide range of fluctuations. The degree of
roughness of the layer results from molten particles becoming
spattered, when they impinge on the surface of the workpiece
which is to be coated. Such pattering may occur to a
greater or lesser degree, depending on the respective
temperature of the particles, with the result that widely
different degrees of roughness may occur on a single ~urface.
When using such surfaces in areas in which on the one hand a
particular level of gripping capacity o~ the surface is
required but on the othar hand the gripping capacity is not
to result in damage to the product, it is not possible to use
the above-described layers, due to the specified fluctuations
in the degree of roughness thereof. In addition, the service
lives of such surfaces are too short, depending on the alloy
used, for many purposes of use. That problem has been
remedied with a moderate degree of ~uccess, by grinding the
sprayed surfaces in a second working operation, thereby
arriving at a defined degree of roughness, within certain
limits.
The present invention provides a surface layer which has a
clearly defined degree of roughness, in a comparatively
simple operating procedure. In particular the process
provides a slip resistant surface.
According to the invention there is provided a process for
producing a slip-resistant surface on a workpiece,
comprising: thermally spraying a surface of the workpiece
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with a powder mixture comprising: a mixture of a hard
material selected from a carbide, boride, silicide, nitride,
oxide and a mixture thereo~ on a matrix of an alloy based on
Ni, Co, Fe or a mixture thereof; wherein the grain-size
distribution o~ said hard material is between 25 to 150 ~m,
and wherein the sprayed but unsintered surface has a
roughness, ~a, in the range of 10 to 100 ~m, wikh a defined
degree of roughne~s o~ Ra.x ~ 20 ~m, wherein x is in the
range of lQ to 100 ~m.
In addi~ion it has been found advantageous for th~ sprayed-on
layer to have a defined degree of surface roughness of Ra.x +
10 ~m: and the hard materials preferably have a melting point
of about 1200~C and higher.
Coating surfaces with a defined degree of roughness of x + 20
~m, preferably ~ 10 ~m, wherein x is the desired sur~ace
roughness in ~m, in the range of 10 to 100 ~m, provide long
service lives when using as the powder material a mixed
powder which comprises two or more components which have a
greater melting interval and hard material. The most
suitable materials for such a matrix are powder materials on
an alloy base of Ni, Co and/or iron. Suitably, the matrix is
based on a nickle based alloy, such as a nickle-chromium-
based alloy which may also contain iron or a nickle-chromium-
boron-silicon alloy. Alternatively, the matrix may be ba~ed
on a cobalt based alloy or an iron based alloyO Suitably,
the grain-size distribution of the matrix alloy is between
150 and 5 ~m. The melting point interval of the alloys
preferably is between 900 and 1400~C, more preferably between
1000 and 1300C, and generally an interval of more than 50C
is suitable.
Hard material particles uch as carbides, borides, nitrides,
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silioides and oxides are used as the carrier for the
roughness. Sui~able particles include tungsten carbide, such
as tungst~n sintered carbide, tungsten carbide-cobalt with a
cobalt content of less than 25% Co. The srain of the hard
material particle may be spherical or polygonal. The ratio
of mixing of the two components, matrix/hard material, may be
between 20 and 80% by weight, preferably 30 to 60% by weight,
for the hard material component. The degree of surface
roughness is influenced by means of the grain-size
distribution or granulometry of the hard material aomponent,
that is to say the maximum component in r~spect of grain-size
distribution is kept very narrow while the overall
distribution is in the ranges of 37 to 125 ~m, 45 to 105 ~m,
45 to 90 ~m, and 37 to 75 ~m, respectively.
The hard material particles are produced by spray drying,
agglomerating with and without sintering or by melting with
subsequent crushing and grindi~g.
A subsequent coating operation of the hard materials, using
Ni, Co and/or Fe, has been found to be advantageous. The
component involved should be below 40~ by weight preferably
20% by weight.
The thermal spraying is suitably by plasma ~lame spraying or
with an autogeneous flame spraying apparatus.
The surfaces which are produced by the above-described
process may be used with particular advantages in the paper
industry, where transport rollers or gripper fingers are
intended to carry thin webs of paper or sheets of cardboard,
without causing the slightest amount of damage to the
material being transported.
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Not only in the preferred areas of use but in quite general
terms, the process according to the invention has been ~ound
to have the particular advantage that during the production
process, a given surPace is produced, which no longer
requires any subsequent treatment.
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