WO1998053140A1

WO1998053140A1 - Composite blade usable in particular in the paper industry

Info

Publication number: WO1998053140A1
Application number: PCT/FR1997/001825
Authority: WO
Inventors: Laurent Kropf; Bernard Hansz; Christian Coddet; Han Lin Liao
Original assignee: Laurent Kropf; Bernard Hansz; Christian Coddet; Han Lin Liao
Priority date: 1997-05-22
Filing date: 1997-10-13
Publication date: 1998-11-26
Also published as: FR2763603A1; FR2763603B1

Abstract

The invention concerns a composite blade (1) usable in particular in the paper industry, comprising a substrate (2) providing the main mechanical properties, an interface coating (3) deposited on at least part of at least one of the surfaces (2a, 2b) of said substrate (2), said coating (3) extending longitudinally along said blade (1) direction and transversely from at least one longitudinal contact edge (3a) and over a predetermined thickness (e) , said coating (3) consisting of a contact material comprising a mixture based on a cohesive complex containing several inert constituents and a modifier of said complex base. The invention is characterised in that the contact material finest thickness (e) in the blade active zone is not less than 60 νm, the contact material (3) comprising on the substrate (2) side, a thickness of at least 5 νm of non-oxidised constituents and, on the contact side, a thickness of at least 5 νm of oxidised constituents.

Description

COMPOSITE BLADE FOR USE IN PARTICULAR IN THE PAPER INDUSTRY

The present invention relates to a composite blade, which can find application in different technical or industrial fields, in particular in the paper industry.

In general, and known per se, the composite blades considered by the present invention comprise:

- A strip of a substrate giving the composite blade most of its mechanical properties, in particular in terms of mechanical strength, flexibility, etc.;

- And an interfacing coating, bonded on one side to the substrate of the strip, directly or indirectly, and adapted on the other side, in particular in shape, to a sliding contact with a medium in movement relative to the blade , this medium can have different consistencies, solid, liquid, viscous or pasty; this interface coating extends longitudinally in the direction of the blade, transversely from at least one longitudinal edge, identical to or different from the longitudinal edge of the strip of substrate, and at least on one of the faces of this same band; and this interfacing coating comprises at least one contact material, in solid form, adapted to resist sliding contact with the treated medium in motion, but different from the substrate.

Such doctor blades whether they are blades designated under the English term of "doctor blade" or blades in direct contact with the external and hard surface of a cylinder, are known and described for example in

GB 978 988, GB 2 295 400, GB 2 128 55 1, EP 0 430 618, US 4 600 599,

US 5,292,382, FR-A- 2,534,608, FR-A-2,534,609 and FR-A-2,534,494. The present invention is explained with respect to the paper industry and relates to a composite blade as defined above which can be used:

- in sliding contact with a coating material in relative movement relative to the blade, in which case it is a doctor blade, or even a blade ("doctor blade"), well known to man profession in the paper industry;

- or in direct contact with the external hard surface of a cylinder ("yankee"), in which case it is a scraper, or a creping blade, or even a cleaning blade, also well known to those skilled in the art in the paper industry.

As regards more particularly the composite coating blades, the properties or characteristics of the interfacing coating, and / or of the contact material, are particularly important for obtaining a coating meeting the requirements of the paper industry, for example in tarnished thickness, uniformity, and surface finish. Thus, the coating material or "coating sauce", behaving like a non-Newtonian fluid, the value of the coefficient of friction of the interfacing coating with respect to the coating sauce is very important, because this coefficient influences the rate of shearing of the coating sauce, which in turn determines the regularity or homogeneity of the coating finally obtained. Likewise, the porosity of the contact material of the interfacing coating plays a major role in obtaining a good quality coating. The subject of the present invention is a new concept of composite blade, making it possible to control or master the properties or characteristics of the interfacing coating, in a manner adapted to the medium treated in movement, for example with respect to the coating sauce, and this during the entire period of use, or lifetime of the composite blade.

In accordance with the invention, it has been discovered that mastering the characteristics of the interfacing coating requires coating the strip of the substrate, with a single and same layer of contact material, substantially continuous and homogeneous practically throughout the thickness of the interfacing coating, i.e. perpendicular to the faces of the strip of the substrate, and this at the observation scale of polarized light microscopy for example. The thickness of this single layer of contact material, that is to say the smallest thickness existing in the active zone of the strip, relative to the corresponding face of the strip, according to the length and / or the width of the latter, must be at least equal to 60 μm.

Consequently, an interfacing coating according to the invention differs from the coatings traditionally obtained until now, by the following two characteristics: - on an appropriate observation scale, for example in polarized light microscopy, and sectional view in the thickness of the contact material, one cannot distinguish the existence of several superimposed elementary layers, delimiting between them one or more discontinuities, always on the scale of observation used; the overall thickness of the interfacing coating, consisting of the only contact material retained, is at least equal to 60 μm, that is to say is greater than the thickness of an elementary layer, such that obtained with the usual techniques of hot spraying of the contact material, for example spraying into a plasma. In addition, and consistent with the technical characteristics defined above, the contact material of the interfacing coating comprises by weight, in homogeneous and isotropic mixture, on the one hand, mainly a cohesive complex base comprising several inert components in mixture , and secondly, in the minority, at least one agent for modifying the complex base, or adjusting at least one characteristic for interfacing the blade with the treated medium in motion.

Preferably, the inert components of the cohesive complex base are metals, and for example different metals, chosen in particular from the group comprising iron, chromium, nickel, tungsten, molybdenum, and copper.

All in all, by using or using all of the technical characteristics expressed above, an interfacing coating is obtained, not only adapted or adaptable to the treated medium in motion, but also having very good properties. intrinsic, in particular due to the specific mass of the contact material, at least equal to 8000 kg / nr, and preferably between 2000 and 19000 kg / m ³ . In particular, the interfacing coatings obtained according to the invention have demonstrated very good resistance to deformations of the composite strip, while remaining integral with the substrate of the strip, in the sense of an absence of peeling between layers and / or by relative to the strip substrate.

To obtain an interfacing coating as defined above, different deposition or coating techniques can be used, for example vapor deposition under vacuum of the contact material, galvano-plasty, etc. Preferentially, but not exclusively, we discovered that:

- By obtaining, or disposing of the contact material in solid form, in particular in discrete form, for example in powder form; - And by projecting this material, in the form of particles on the strip of the substrate, in a gas flow at high temperature, in particular obtained by combustion of a fuel, and having a supersonic linear speed;

- An interfacing coating is obtained directly on the substrate of the strip, having the different characteristics or properties stated and discussed previously.

The present invention is now described with reference to the accompanying drawing, in which:

- Figure 1 shows a sectional view of a composite blade according to the invention, as used for coating on a strip of paper; - Figure 2 shows a top view of the composite blade, in its position shown in Figure 1, and before use.

Traditionally, a composite blade 1 comprises:

- A strip 2 of a substrate giving the blade most of its mechanical properties; an interfacing coating 3, bonded on one side to the substrate of the strip 2, and adapted on the other side, in particular in shape and in size, in sliding contact with the coating sauce 4 in relative movement relative to the blade ; the interfacing coating 3 extends longitudinally in the direction of the blade, that is to say perpendicular to the plane of FIG. 1, and transversely, that is to say say downwards and in the plane of FIG. 1, from at least one longitudinal edge 3a, and at least on one 2a of the faces of the strip;

Depending on the coating parameters, and on the equipment, in particular blade holder, in which the composite blade is mounted, the person skilled in the art knows how to adapt, and has described different profiles, in particular bevel, of the coating 3 for interfacing. , and possibly the strip 2 of the substrate, adapted to each other and to the required coating conditions.

According to the invention, it is the interfacing coating 3, and its constituent contact material, which are obtained as described above, in particular with the minimum thickness (e) shown in FIG. 1, and at least equal to 60 μm in the active area of the slide.

As shown in FIG. 1, the contact coating 3 adheres directly to the substrate of the strip 2. The substrate of the strip 2 consists of at least one metallic steel, for example by a hardened steel, having a grade as used for the manufacture of springs. However, the substrate of the strip 2 can also consist of a polymeric material, composite or not.

The longitudinal edge 3a of the interfacing coating 3 is aligned or superimposed with the longitudinal edge 2c of the strip 2. The interfacing coating 3 extends transversely on the face 2a of the strip 2, from the entry edge 3a up to an exit edge 3c. Of course, this interfacing coating 3 can also extend on the other face 2b of the strip 2.

Alternatively, the interfacing coating 3 can be bonded to the strip 2 by an appropriate adhesive intermediate layer, although the direct deposition of the contact material on the substrate of the strip 2 constitutes a preferred form of the invention.

Regarding the contact material, the blade interfacing characteristic (s), controlled or adjusted by the modifying agent, are:

the porosity of the interfacing coating 3 or of the contact material, expressed as a percentage of the internal surface of said material relative to the apparent surface of interfacing coating; for example, this porosity is less than 4%; - And / or the coefficient of friction of the coating 3 of interfacing with respect to the moving medium 4;

- And / or the wettability of the external surface 3b of the interfacing coating 3, in contact with the moving medium 4; - And / or the hardness of the interfacing coating 3; preferably, this hardness is at least equal to 700 Vickers.

For the purposes of checking or adjusting the above characteristics, the cohesive and aggregated complex base represents by weight, between 75% and 95%, and preferably between 80% and 90% of the contact material. Preferably, the modifier (s) are non-metallic, and in particular metalloids chosen from the group comprising carbon, silicon, and boron. This modifier can also be a plastic, or a polymer.

Thus, by oxidizing molybdenum, the hardness is increased and the coefficient of friction of the interfacing coating is reduced; and by boronizing the iron, the hardness is increased and the coefficient of friction of this same coating is reduced.

The characteristic or characteristics of the interfacing coating can also be controlled, by chemically modifying at least one inert compound of the cohesive complex base of the contact material, by oxidation, or boruration, or carburation, that is to say by introducing in the crystal lattice or not of the cohesive complex base, all appropriate interstitial elements.

The work carried out on this type of blade has shown that the choice of metal particles projected on the substrate as well as their weight content in the mixture were important. Likewise, the structure of the coating could lead to different properties depending on the destination of the blade.

In fact, when the coating is carried out in several passes on the substrate, the reactivity of the particles with air substantially modifies the properties of said coating, in particular its attachment power or its wettability. It has been found that it is preferable to choose a contact material which comprises, on the side of the substrate, a thickness of at least 5 μm of non-oxidized components and, on the side of the contact edge, of at least a thickness of 5 μm of oxidized components. In this way, a good direct attachment of the coating to the substrate is achieved and the coating, on the side of the contact edge, is given the good wettability necessary in the application as a contact scraper sliding on a coating material. As inert components, surfactants selected from the group comprising especially B, Si, Al, Mn, Ti, Ag, Mo, which can be supplemented with metals such as Fe, Cr, Ni. The weight contents can vary between certain limits, reduced to the total weight of the coating deposited on the substrate. Thus the contents in the mixture of the cohesive base can be:

B from 0.5 to 6% If from 0.2 to 10% Al from 1 to 20% Mn from 0.6 to 3%

Ti from 1 to 85% Ag from 0.2 to 3% Mo from 1 to 20% Fe from 0.5 to 4% Cr from 4 to 17%

Nor in addition to 100%

The components which provide good hardness to the coating are preferably chosen from B, Si, Mn, Ti, Mo and Fe, while the wettability is imparted by the oxides of these same components, in a fairly large proportion and / or by the oxides of Al, Cr, Ni. The hardness of the coating is also improved by incorporating carbon as a modifying agent, for example in a content by weight of between 0.5 and 30%.

A coating according to the invention and produced with pure titanium has given excellent results with regard to the attachment to a steel substrate and to the wettability imparted by the titanium oxides nitrides which have formed with the nitrogen of the air during the plasma projection of the titanium particles in the last passes of the plasma torch.

In the particular application of the blade according to the invention, as a sliding doctor blade with a coating material, it is preferable to produce a coating having a porosity of less than 4% by volume, the surface size of the pores not exceeding 20 μm ² . Preferably, at least 80% of the porosity is made up of pores whose surface size is less than 10 μm ² . The recommended porosity made it possible to note that the rheological problems were avoided during coating, the best results having been obtained when 90% of the porosity consisted of pores whose surface size was less than 10 μm ^.

To obtain an interfacing coating as defined above, preference is given to other deposition techniques such as vacuum vapor deposition, electroplating, etc. which may also be suitable, plasma spraying onto the substrate, particles of one or more metallic components indicated above, in a gas flow at high temperature and at very high speed (supersonic). Various thermal spraying techniques are available such as, for example, the so-called HVOF ("high velocity oxy fuel") technique implemented for example in the CDS device manufactured by SULZER-METCO.

According to a first embodiment, the metal particles are projected directly onto the substrate, each passage or pass of the plasma torch being carried out longitudinally in the direction of said blade and transversely from at least the longitudinal contact edge of said blade, and so that the residence time between the point of impact of the molten particle on the substrate and its cooling point is as short as possible, which avoids the formation of oxides which would be detrimental to a good adhesion of said particles on the substrate. This reduced residence time is maintained at each passage of the plasma torch until at least a thickness of 5 μm of coating has been formed. Then the major part of the coating is deposited, increasing, if desired, the cooling time of the molten particles deposited on the substrate. In any case, for at least the last five microns of the coating, it is cooled more slowly so as to form oxides.

According to another embodiment, a sub-layer can be deposited on the substrate before proceeding with the plasma spraying of the particles, the thickness of the sub-layer which is preferably a sub-layer. Ni-Cr or Ni-Al layer is weak compared to the thickness of the coating itself which is of the order of a millimeter.

It is also possible according to the invention to use the surfactants with a ceramic matrix of the alumina, zirconia and other type. Likewise, the surfactants are used in the pure state or in the partially or totally oxidized, nitrided or carburized state, the supplements being able to be metals or ceramics.

The composite blade according to the invention comprises a contact material comprising at least 80% of pure titanium and approximately 15 to 20% of titanium oxynitride on the surface.

Claims

REVEN DICATIONS

1. Composite blade (1) comprising a strip (2) of a substrate giving said blade most of its mechanical properties, an interface coating (3), bonded on one side to said substrate, and adapted from the on the other side, in particular in shape, in sliding contact with a medium (4) in relative movement relative to said blade, said interfacing coating (3) extending longitudinally in the direction of said blade, and transversely from at least one longitudinal edge (3a), and at least on one (2a) of the faces of the strip, and said interfacing coating comprising at least one contact material, adapted to resist sliding contact with said moving medium, and different from the substrate, the interfacing coating (3) comprising a single layer of contact material, substantially continuous and homogeneous practically throughout the thickness of said coating, characterized in that the contact material comprises by weight , in homogeneous and isotropic mixture, on the one hand, mainly, a cohesive complex base comprising several inert components in mixture, and on the other hand, in the minority, at least one agent for modifying said complex base, or adjustment of at least one characteristic of interfacing said blade with the moving medium, and of which the smallest thickness (e) relative to the strip, and in the active zone of the blade according to the length and / or the width of the latter, is at least equal to 60 μm.

2. Composite blade according to claim 1, characterized in that the contact material comprises, on the side of the substrate, a thickness of at least 5 μm of non-oxidized components and, on the side of the contact edge, of at least one 5 μm thickness of oxidized components.

3. Composite blade according to claim 2, characterized in that the components are surfactants chosen from the group comprising B, Si, Al, Mn, Ti, Ag, Cu, Mo, and which can be supplemented with metals such as Fe, Cr, Ni whose contents in the mixture are: B from 0.5 to 6%

If from 0.2 to 10%

Al from 1 to 20%

Mn from 0.6 to 3% Ti from 1 to 85%

0.2 to 3% Ag

1 to 20% MB

Fe from 0.5 to 4%

Cr from 4 to 17% Ni in addition to 100%

4. Composite blade according to claims 2 or 3, characterized in that the surfactants are used in the pure state or in the partially or fully oxidized, nitrided or carburized state, the supplements possibly being metals or ceramics.

5. Composite blade according to one of claims 2 or 3, characterized in that the surfactants are used with a ceramic matrix, for example an alumina or zirconia matrix.

6. Composite blade according to claim 2 or 3, characterized in that the contact material has on the surface and on the scale of a micrographic observation a porosity whose surface size of the pores does not exceed 20 μm ² .

7. Composite blade according to claim 6, characterized in that 90% of the porosity is constituted by pores whose surface size is less than 10 μm ² .

8. Composite blade according to claim 1, characterized in that the modifying agent is carbon, the content of which in the mixture is between 0.5 and 30%.

9. Composite blade according to claim 1, characterized in that the interfacing coating is bonded to the substrate by an intermediate layer.

10. Composite blade according to claim 1, characterized in that the contact material comprises at least 80% of pure titanium and approximately 15 to 20% of titanium oxynitride on the surface.

11. Composite blade according to claim 1, characterized in that the cohesive complex base represents by weight, between 75% and 95%, and preferably between 80% and 90% of the contact material.

12. Composite blade according to claim 1, characterized in that the substrate of the strip consists of a polymeric material, composite or not.

13. A composite blade according to claim 1, characterized in that the longitudinal edge (3a) of the interfacing coating is aligned or superimposed with the longitudinal edge (2c) of the strip (2).

14. Composite blade according to claim 1, characterized in that the interfacing coating (3) extends transversely, over one (2a) and / or the other (2b) facing the strip (2).

15. A composite blade according to claim 1, characterized in that the interfacing coating (3) is bonded to the strip (2) by an adhesive intermediate layer.

16. A method of manufacturing a blade according to any one of claims 1 to 15, characterized in that the contact material is available in solid form, in particular in discrete form, for example in powder form, and it is projected said material on the strip (2) of the substrate, in a high temperature gas flow, in particular obtained by combustion of a fuel with an oxidizer, and having a supersonic linear speed.

AMENDED CLAIMS

[received by the International Bureau on March 03, 1998 (03.03.98); claims 1 and 16 replaced by claims 1 and 12 amended

(3 pages)]

1. Composite blade (1) comprising a strip (2) of a substrate giving said blade most of its mechanical properties, an interface coating (3), bonded on one side to said substrate, and adapted from the on the other side, in particular in shape, in sliding contact with a medium (4) in relative movement relative to said blade, said interfacing coating (3) extending longitudinally in the direction of said blade, and transversely from at least one longitudinal edge (3a). and at least on one (2a) of the faces of the strip, and said interfacing coating comprising at least one contact material, adapted to resist sliding contact with said moving medium, and different from the substrate, the interfacing coating (3) comprising a single layer of contact material, substantially continuous and homogeneous practically throughout the thickness of said coating, characterized in that the contact material comprises by weight, in homogeneous and isotropic mixture, of a firstly, 0 mainly, a cohesive complex base comprising several inert components in admixture, and secondly, at least, at least one agent for modifying said complex base, or setting at least one interface characteristic of said blade with the moving medium, and of which the smallest thickness (e) relative to the strip, and 5 in the active zone of the blade according to the length and / or the width of the latter, is at least equal to 60 microns, said contact material comprising, from the substrate side, a thickness of at least 5 .mu.m unoxidized components and, of the contact edge side, at least a thickness of 5 microns of oxide components. 0 2. composite blade according to claim 1. characterized in that the components are surfactants chosen from the group comprising B, Si, Al, Mn, Ti, Ag, Cu, Mo. and can be supplemented with metals such as Fe, Cr, Ni whose contents in the mixture are:

5 B from 0.5 to 6% If from 0.2 to 10%

Al from 1 to 20%

Mn from 0.6 to 3%

Ti from 1 to 85% Ag from 0.2 to 3%

1 to 20% MB

Fe from 0.5 to 4%

Cr from 4 to 17%

Nor in addition to 100% 3. Composite blade according to claims 1 or 2, characterized in that the surfactants are used in the pure state or in the partially or fully oxidized, nitrided or carburized state, the supplements being able to be metals or ceramics.

4. Composite blade according to one of claims 1 or 2, characterized in that the surfactants are used with a ceramic matrix, for example an alumina or zirconia matrix.

5. A composite blade according to claim 1 or 2, characterized in that the contact material has, on the surface and on the scale of a micrographic observation, a porosity whose surface pore size does not exceed 20 μm ² .

6. Composite blade according to claim 5, characterized in that 90% of the porosity consists of pores whose surface size is less than 10 μm ² .

7. Composite blade according to claim 1, characterized in that the modifying agent is carbon whose content in the mixture is between 0.5 and 30%.

8. Composite blade according to claim 1, characterized in that the contact material comprises at least 80% of pure titanium and approximately 15 to 20% of titanium oxynitride at the surface. 9. Composite blade according to claim 1, characterized in that the cohesive complex base represents by weight, between 75% and 95%, and preferably between 80% and 90% of the contact material. 10. Composite blade according to claim 1, characterized in that the substrate of the strip consists of a polymeric material, composite or not.

11. Composite blade according to claim 1, characterized in that the longitudinal edge (3a) of the interfacing coating is aligned or supeiposed with the longitudinal edge (2c) of the strip (2).

12. Composite blade according to claim 1, characterized in that the interfacing coating (3) extends fransversalement, on one (2a) and / or the other (2b) face of the strip (2).