FR2541610A1 - METHOD FOR APPLYING A WEAR RESISTANT AND / OR CORROSION RESISTANT COATING ON AN ARTICLE HAVING AN IRREGULAR SURFACE - Google Patents

Abstract

THIS PROCESS CONSISTS OF PROVIDING ON AN ARTICLE 14 TO TREAT A SHEET INCLUDING PARTICLES OF A HARD MATERIAL, SUCH AS TUNGSTENE CARBIDE OR ANY OTHER CARBIDE, DISTRIBUTED IN A MATRIX COMPOSED OF POLYTETRAFLUOROETHYLENE FIBERS INTERLACED WITH SUCH SHEET, THIS SHEET IMMEDIATE BUT NOT IN DIRECT CONTACT WITH THE ENTIRE EXTENT OF THE IRREGULAR SURFACE 12 TO BE COVERED, TO PLACE THE said IRREGULAR SURFACE, AND THE SOLDERING AND HARD COATING MATERIAL THUS POSITIONED IN A FLEXIBLE ENCLOSURE 18 SENSITIVE TO PRESSURE, TO APPLY ON THE EXTERNAL FACE OF THE ENVELOPE TO CAUSE ITS SAGGING AND OBLIGATE IT TO APPLY THE SHEET 10 IN CLOSE CONTACT ON THE IRREGULAR SURFACE 12 TO BE COVERED, THEN TO SUBMIT THE ARTICLE THUS TREATED TO A SUFFICIENT TEMPERATURE TO USE THE POLYTEHETRICE AND CAUSE THE HARD COATING MATERIAL TO FORM A CONSISTENT MASS WHICH IS THEN FIXED TO THE IRREGULAR SURFACE OF THE ARTICLE.

Description

The present invention relates to a means for

  attaching a coating material to a configuration surface

irregular ration.

  The present invention relates more particularly-

  means for attaching a hard, particulate, solid coating material to at least part of a surface of

irregular configuration.

  It is standard practice in the appliance industry.

  apply hard coating materials to various items.

  However, when it is desired to apply a coat evenly

  Many such problems are frequently encountered with such materials on an article having an irregularly shaped surface. In this respect, various electrolytic deposition methods are known for coating surfaces, but these techniques

  are limited to situations in which one wishes to learn

  apply a layer of relatively thin material

  mount this type of problem, we usually use tech-

  spray nicks in which one wishes to obtain

  relatively thick layers However, the large in-

  One of the problems encountered in the case of this solution is that, since these techniques operate in a straight line, the thickness of the resulting coating can be very irregular. Another solution for depositing

  thick coatings consist of a weld reload.

  However, here too, unless you have easy access

  around the surface of the article to be coated, the cor-

  The main aim of this invention therefore is to provide the means for depositing a uniform coating.

  relatively thick hard coating material on an over-

  face of irregular configuration.

  The present invention mainly relates to a

  process for applying a hard coating material,

  wear-resistant and / or corrosion-resistant on a

  irregular surface of a given article, which process

  is to procure an article having an irregular surface

  lière and that it is a question of coating with a material of coating-

  hard to provide a suitable brazing material for

  come into contact with at least part of the ir-

  regular and cover it, to position a sheet of hard coating material distributed in a fibrous polytetrafluoroethylene matrix, in the immediate vicinity but not in total direct contact with the irregular surface.

  to coat, to surround the irregular surface, as well as the

  brazing and hard coating material positioned in this way,

  in a flexible pressure-sensitive envelope, to be applied

  quer a pressure on the outer surface of the envelope to

  force it to flex and, in this way to apply the sheet-

  the hard coating material by force in direct contact

  with the irregular surface, and to submit the article thus

  if treated at a temperature sufficient to oblige the poly-

  tetrafluoroethylene to volatilize and the coating material

  hard and soldering to form a coherent mass which

  is related to the irregular surface of the article.

  Other objects and advantages of the invention appear

  tront during the description which follows To the drawings

  attached, given only as an example, Fig 1 is a schematic representation

  a suitable device for the implementation of the pre-

  invention; and Fig 2 is an enlarged sectional view of part of a threaded steel rod carrying a resistant coating which is applied to it as indicated

of the present invention.

  The preferred embodiment of the present invention will be illustrated below in connection with the following example, in which the threaded part of a steel screw,

  12.7 mm in diameter, was coated with tungsten carbide-

  Tene contained in a brazing alloy rich in nickel.

Example

  We got a steel screw 50.8 mm long and 12.7 mm in diameter We cleaned the screw

  by shot blasting of its surface The screw had 10.236 fi-

  lets per linear centimeter (13 threads per linear inch

  neary). A sheet of hard coating material 10 has been laid loosely over the threads 12 of the screw 10 The sheet 10 has a polytetrafluoroethylene matrix

  in fibrils which traps a solid particulate matter

  composed of 65% by volume of tungsten carbide and

  35% by volume of a nickel-rich alloy similar to this

  him known as AMS 4775 This sheet was held in place by an adhesive material 16 deposited in a thin layer along the periphery of the fabric However, it is not essential to use

  an adhesive The sheet material can be simply put

  sitionée on the article on which it is to apply.

  The screw, provided with the sheet of coating material

  hard mold wrapped around it was placed in a flexible rubber mold The mouth 20 of the mold was closed with a suitable rubber stopper 22 Then the mold was subjected to an external pressure (l device is not shown) This was achieved through the use of an isostatic press in which the pressurizing fluid was water Naturally, other means can be used to exert external pressure and , since the pressurizing means are not part of the present invention, these

  other means will not be described in this specification.

  The threaded rod provided with a layer or sheet of hard coating and brazing material in contact with its threads was then placed in an oven and heated to a temperature of about 1093 OC (2000 'F) under vacuum, to cause decomposition of polytetrafluoroethylene

  and bring the hard coating and brazing material to form

sea a fixed coherent mass.

  The present invention can be used for

: 2541610

  apply hard coating material to any item

  conch with an irregular surface and which does not come off

  neither composes nor softens significantly when heated

  fe at a temperature sufficient to fix or adhere

  hard coating material Typical examples of such substrate materials are steels, nickel,

  cobalt, titanium and their respective alloys.

  The expression "sheet of hard coating material" as used in the present specification means a material of the type described in the US Pat.

  E.U A no 4 194 040 More specifically, the coating sheet

  hard is essentially made up of around 85 to

  about 99%, by volume of a solid particulate matter

  roughly uniformly distributed in a matrix

  having about 1 to about 15% by volume and made of

  polytetrafluoroethylene resin in fibrils,

  shines of this polytetrafluoroethylene bonding and trapping the particulate matter to give cohesion and

flexibility to the sheet.

  The process for producing the sheet material used in the implementation is described in US Patent No. 3,864,124 More specifically, this material

  sheet is produced by a process which consists in tra-

  mechanically working, for example by rolling, milling

  ball mill stretching, stretching, spreading and equi

  are worth, a mixture composed of polytetrafluoroethylene and the particulate substance to form a sheet or sheet which has a high mechanical strength in the green state and a low modulus of elasticity This sheet or this

  the tablecloth can then be shaped to a desired configuration

  heated and heated to a temperature at which diffusion and / or fusion occur Polytetrafluoroethylene is transformed into a matrix of fibrils under the effect of

  mechanical work under the specified conditions These fi-

  shells have a diameter of less than 10 microns and, generally

  Lement, a length / diameter ratio of 10/1 to 100/1 or more The sheet or tablecloth produced is distinguished by low elastic moduli, that is to say by good drapability and good flexibility , analogous to

  those of the fabrics, and which allow it to adjust

  closely around articles of different shapes and sizes

  push these items, despite its very heavy load in

  particulate matter The filler particles of the film

  the according to the invention are not linked to each other by chemical or metallurgical bonds in the composition

  flexible nonwoven according to the invention -

  The mechanical work of the mixture, executed in the fa-

  lesson described, causes a transformation of polytetrafluoro-

  ethylene into fibrils and brings the resulting fibrils

  to trap and bind together the particular materials

  res to produce a type of nonwoven sheets or webs which have good flexibility and high mechanical strength in the green state. In other words, by subjecting the above-mentioned mixtures to mechanical work in the manner described below, it is produces a three-dimensional matrix of interleaved and intertwined fibrils, in which the material matter is uifon from it and the solid particulate matter used in the

  sheet material may be an abrasive material

  metallic chosen from the group composed of carbides, ni-

  trures, silicides or their mixtures The particular material

  the surface may additionally contain a brazing alloy

  In practice, it is preferable that the material

  wear resistant either a carbide selected from the group consisting of tungsten carbide, chromium carbide, tantalum carbide, titanium carbide, molybdenum carbide, silicon carbide, boron carbide and mixtures of these carbides

  The brazing alloys which are suitable include

  take alloys based on nickel, cobalt or

  iron, preferably alloys with rock hardness

  well of at least 40 on the C scale In addition, alloys can also be used with good results

  based on nickel, cobalt, copper or silver possessed

  with a melting point of less than 1,200 OC In any case,

  the particular brazing alloy used is not critical

  as for the implementation of the invention, given that

  brazing alloys are well known in the art.

  All that is required is that the brazing alloy form

  me a matrix with high mechanical resistance and binds the ma-

  hard coating with an irregular surface.

  In certain applications, the functions of the wear-resistant material and of the brazing constituent can be ensured by the same constituent, for example, by a hybrid brazing Typical examples of such hybrid brazing include nickel-based brazing of the type described in material standards AMS-4775, 4776

and 4777.

  The brazing material can be applied either directly to the surface to be coated, or in the form of a fabric produced in accordance with the patent specifications.

  E U A N O 4 194 040, that is, it can be in-

  embedded in the hard coating sheet It can be applied in the form of a separate sheet of material,

  or it can be applied in the form of a stra-

  tified superimposed on a sheet of hard coating material.

  It is clear from the above that the pro-

  transferred according to the invention constitutes a unique process for app-

  applying wear-resistant material to the surface of an irregularly shaped article to improve its physical properties The invention can be applied, for example

  to process tool tips or the like for

  improve their functional characteristics.

Claims (1)

CLAIMS 1 Method for applying a hard wear-resistant coating to an article having an irregular surface, characterized in that it consists for an article (14) having an irregular surface (12) which is to coat with a hard coating material, to provide a brazing material suitable for coming into contact with at least part of said irregular surface (12) and for coating this part, for positioning a sheet of material - re hard coating (10) distributed in a fibrous matrix of polytetrafluoroethylene in the immediate vicinity of said irregular surface (12) but not in direct direct contact with this surface, to surround said irregular surface ( 12) as well as the brazing and hard-coating material, in a flexible envelope (18) sensitive to pressure, to apply pressure to the external face of said envelope (18) to force it to flex and , in this way, to force said leaf the hard coating material (10) to be applied in direct contact with said irregular surface (12); and subjecting the article (14) thus treated to a temperature sufficient to cause the volatilization of said polytetrafluoroethylene and to force the hard coating material to form a coherent mass which is fixed to the irregular surface (12) of article (14). 2 Method according to claim 1, characterized in that said sheet of hard coating material is essentially composed of between about 85 to about 99% by volume of a solid particulate matter distributed approximately uniformly in a matrix representing between about 1 and about 15% by volume of fibrillated polytetrafluoroethylene resin, the fibrils of said polytetrafluoroethylene bonding and trapping said particulate material to impart cohesion and flexibility to said sheet. 3 Method according to claim 2, characterized in that said particulate material is an intermetallic abrasive material selected from the group consisting of carbides, nitrides, borides and silicides or their mixtures. 4 Method according to claim 3, characterized in that said intermetallic abrasive material is a carbide chosen from the group consisting of tungsten carbide, chromium carbide, tantalum carbide, titanium carbide, molybdenum carbide, silicon carbide, boron carbide or mixtures of these products. Process according to Claim 1, characterized in that the brazing alloy is an alloy chosen from the group composed of alloys based on nickel, cobalt or iron. 6 Method according to claim 1, characterized in that said brazing alloy is an alloy based on nickel, cobalt, copper or silver. 7 Method according to claim 1, characterized in that the brazing material also plays the role of hard coating. 8 The method of claim 1, wherein the surface to be coated with said hard coating material is first coated with a brazing alloy. 9 Method according to claim 1, characterized in that said brazing material is incorporated in said sheet of hard coating material.   1 O Method according to claim 1, character-   laughed in that said brazing material is applied to   said irregular surface in the form of a dry sheet   adorned with material composed of a particular brazing material   ring dispersed in a polytetrafluoroethyl matrix fibrillated lene.   ll The method according to claim 1, character-   dried in that said brazing material is applied to said irregular surface in the form of a sheet of material which has been laminated on a hard coating sheet composed of a particulate hard coating material   dispersed in a matrix of polytetrafluoroethylene brilléeo