EP0605585B1 - Method for making a composite part with an antiabrasion surface, and parts obtained by such method - Google Patents

Abstract

The method for making a composite part with an antiabrasion surface (2) is characterized by providing a substrate (1) whose shape and surface are appropriate to receive by gluing surface elements of antiabrasion material (2), by making one or a plurality of surface elements of antiabrasion material (2) by infiltration of a binding alloy in a stack of tungsten carbide grains, and by adhering the antiabrasion surface elements (2) on the substrate (1) by gluing with an epoxy glue (3).

Description

The present invention relates to the manufacture of composite metal parts comprising a contact coating intended to resist abrasion.

Such mechanical parts known as “wearing parts” are known, which are superficially reinforced by the addition of a material having improved characteristics in terms of resistance to wear by abrasion.

The present invention relates more particularly to hard reloads using a structure of grains of high hardness bonded together by a metal alloy which is commonly referred to as the metallic matrix. The grains of high hardness can advantageously be grains based on tungsten carbide.

A first known technique for producing an abrasion-resistant coating is hard surfacing by welding. For example, rigid rods or flexible rods are used, one end of which is applied to the surface to be recharged and is subjected to an electric arc or to an oxyacetylene flame. The rod includes a tungsten carbide powder embedded in an alloy based on nickel or other suitable metals.

Such hard surfacing obtained with tungsten carbide rods has drawbacks, however: in particular, the welding processes lead to depositing the surfacing in the form of successive beads, juxtaposed side by side one after the other. It is understood that the realization of a relatively large area using such a technique is tedious, and requires a certain dexterity and a certain habit on the part of the operator. On the other hand, the waves inherent in such a material deposition process, reproducing the shape of the successive beads, cause thickness irregularities of up to several millimeters.

As a result, this technique does not make it possible to produce parts whose dimensions are precise, or whose shapes are complex.

Document FR-A-814 171 describes a process for producing a shaped part by sintering in the liquid phase, in which a mixture of carbide chips and molten metal powder is introduced into a carbon mold. The shaped part is melted under pressure. Such a process causes, during the fusion, a significant dimensional shrinkage.

Also known, from document US-A-4 307 845, a crusher comprising solid ceramic bars fixed by gluing to an intermediate support piece itself secured to the crusher by a bolt. This document contains no teaching relating to the manufacture of the solid ceramic bar, and its object is far removed from the production of an abrasion-resistant coating.

A more advanced technique for producing a layer of abrasion-resistant material is described in document FR-A-1 398 732. It is an infiltration technique, in which a hollow mold made of carbon or ceramic material is used having a desired shape; a metal substrate is placed in the hollow of the mold, opposite the mold molding walls; filling with grains of tungsten carbide or equivalent the hollow interior space between the substrate and the mold molding walls, vibrating the assembly to pack the grains; grains or pellets of metal or of alloy binder are placed above the grains of carbide; the assembly is heated to a temperature above the melting temperature of the alloy and below the melting temperature of the core and the mold. The rise in temperature ensures the melting of the alloy or binder metal, which infiltrates into the space filled with tungsten carbide grains, and ensures the welding with the metal substrate. It is then left to cool and can be removed from the mold.

This infiltration technique is quite suitable for parts in which a convex substrate is of relatively small dimensions, and of relatively compact shape, the abrasion-resistant layer being relatively massive. The technique is also suitable when the substrate is concave.

However, when trying to apply this infiltration technique to parts in which the substrate has a convex shape, in particular parts whose surface is relatively important in relation to its volume, the inventors have found that the abrasion-resistant coating tends to break under the action of impacts, and that in particular this coating does not allow subsequent re-machining after infiltration. The weld between the thickness of the abrasion-resistant material and the metal substrate is of poor quality.

For example, this technique of infiltration on a metal substrate does not allow the production of a part that is mechanically strong enough to constitute a needle for a needle valve used in hydroelectric plants. Indeed, during the closing of the needle on its seat, the anti-abrasion coating of the needle tends to burst under the effect of shocks and mechanical stresses occurring at this closing time.

Likewise, this technique of infiltration on a metal substrate does not make it possible to produce teeth of aluminum mixer having sufficient qualities of mechanical resistance.

SUMMARY OF THE INVENTION

The problem proposed by the present invention is to ensure satisfactory mechanical resistance to an abrasion-resistant coating based on infiltrated tungsten carbide grains covering a substrate of a different nature, the assembly constituting a composite part. Such a composite part must have qualities of mechanical resistance at the surface sufficient to withstand shocks, and to allow possible re-machining of its abrasion-resistant coating surface without cracking or falling apart.

The idea which is the basis of the present invention is that the defects observed in mechanical strength of the abrasion-resistant coatings based on tungsten carbide grains produced by infiltration on a substrate would result from differential expansions occurring during infiltration. In fact, during infiltration, the entire substrate and the surface reloading of tungsten carbide grains must be brought to a temperature sufficient for the melting of the alloy or binder metal which must infiltrate into space. filled with tungsten carbide grains and which must ensure the weld with the substrate. During this heating, the metal substrate expands appreciably, while the grains of tungsten carbide which form a compact stack expand very little, roll on each other and can thus follow the expansion of the mold and the substrate. After infiltration, when the assembly is cooled, the substrate tends to contract, while the very compact stacking of tungsten carbide grains contracts very little. This results in significant mechanical stresses at the interface between the substrate and the layer of abrasion-resistant material which covers it. These significant mechanical tensions are probably the source of the mechanical resistance defects observed on the parts thus recharged by infiltration on a substrate, as well as the defects observed on the weld between the abrasion-resistant coating and the metal substrate.

During heating to obtain infiltration, the tungsten carbide grains tend to roll over each other, which allows them to occupy all the space between the mold and the substrate.

When the assembly cools, the tungsten carbide grains no longer have the possibility of rolling over one another, since they are bonded by the alloy or binder metal, so that the abrasion-resistant coating can no longer be shrink by a coefficient similar to that of the substrate.

Despite these defects in mechanical resistance to impacts, abrasion-resistant parts obtained by infiltration appear advantageous, because the abrasion-resistant surface thus obtained by infiltration exhibits remarkable properties of abrasion resistance. On the other hand, infiltration makes it possible to produce abrasion-resistant surfaces having particularly regular and smooth shapes, promoting the efficiency of the parts thus produced. For example, in the case of a valve needle for a hydroelectric plant, such a needle must have a very regular conical surface allowing efficient sealing. In the case of a kneading tooth or a paving stone of a kneading cylinder, the surfaces must also be regular, so as not to impede the flow of the fluid to be kneaded.

The object of the present invention is therefore to produce parts for which the abrasion-resistant coating is obtained by infiltration of alloy into a stack of tungsten carbide grains, these parts having, after production, markedly improved qualities of mechanical resistance to impact resistance. , avoiding separation between the substrate and its abrasion-resistant layer.

According to the invention, such parts with abrasion-resistant coating can be obtained at low cost, in particular when the parts are large dimensions, lowering costs being obtained in particular by reducing the risk of waste.

Another advantage of the invention is that it becomes possible to produce relays or abrasion-resistant coatings on substrates which are themselves liable to not withstand temperatures as high as that necessary for melting the alloy or binder metal during infiltration. It is thus possible to design a part made of composite material in which the substrate can be non-metallic, associated with a layer of abrasion-resistant material based on infiltrated tungsten carbide grains.

• a) prévoir un substrat en acier présentant une forme générale convexe et un état de surface approprié pour recevoir par collage des éléments de revêtement en matière antiabrasion à base de grains de carbure de tungstène,
• b) réaliser, par infiltration d'un alliage liant dans un empilement de grains de carbure de tungstène, un ou plusieurs éléments de revêtement en matière antiabrasion, comportant une face interne concave conformée pour s'adapter sur la surface convexe du substrat, et comportant une face externe conformée pour constituer la face antiabrasion de la pièce composite à réaliser,
• c) solidariser par collage le ou les éléments de revêtement en matière antiabrasion sur la surface convexe du substrat, en appliquant lesdits éléments de revêtement sur le substrat avec interposition d'une couche appropriée de colle.

To achieve these and other objects, the present invention provides a new method of producing a composite part with an abrasion-resistant coating, the part comprising at least one substrate covered with a layer of abrasion-resistant material based on carbide grains. tungsten, the process comprising the following steps:

• a) providing a steel substrate having a generally convex shape and a surface condition suitable for receiving by bonding coating elements made of abrasion-resistant material based on tungsten carbide grains,
• b) producing, by infiltration of a binder alloy in a stack of tungsten carbide grains, one or more coating elements made of abrasion-resistant material, comprising a concave internal face shaped to fit on the convex surface of the substrate, and comprising an external face shaped to constitute the abrasion-resistant face of the composite part to be produced,
• c) securing by bonding the coating element or elements of abrasion-resistant material to the convex surface of the substrate, by applying said coating elements to the substrate with the interposition of an appropriate layer of adhesive.

• a) prévoir un substrat en tôle cintrée en demi-cylindre dont l'état de surface intérieure est approprié pour recevoir par collage des éléments de revêtement en matière antiabrasion à base de grains de carbure de tungstène,
• b) réaliser, par infiltration d'un alliage liant dans un empilement de grains de carbure de tungstène, plusieurs éléments de revêtement en matière antiabrasion, comportant une face interne conformée pour s'adapter sur la surface intérieure du substrat, et comportant une face externe conformée pour constituer la face antiabrasion de la pièce composite à réaliser,
• c) solidariser par collage les éléments de revêtement en matière antiabrasion sur la surface intérieure du substrat, en appliquant lesdits éléments de revêtement sur le substrat avec interposition d'une couche appropriée de colle, réalisant un pavage de plaques en matière antiabrasion suivant la courbure de surface intérieure de demi-cylindre.

According to a particular application, the present invention provides a new method for producing a shielding plate for an aluminum mixer with an abrasion-resistant coating, the plate comprising at least one substrate covered with a layer of abrasion-resistant material based on carbide grains. of tungsten, the process comprising the following steps:

• a) provide a sheet metal substrate bent into a half-cylinder whose interior surface condition is suitable for receiving elements by bonding coating in abrasion-resistant material based on tungsten carbide grains,
• b) producing, by infiltration of a binding alloy into a stack of tungsten carbide grains, several coating elements made of abrasion-resistant material, comprising an internal face shaped to fit on the internal surface of the substrate, and comprising an external face shaped to constitute the abrasion-resistant face of the composite part to be produced,
• c) joining the coating elements made of abrasion-resistant material to the interior surface of the substrate by bonding, by applying said coating elements to the substrate with the interposition of an appropriate layer of adhesive, paving plates of abrasion-resistant material along the curvature inner surface of half cylinder.

According to a first possibility, the substrate can be made of steel. The glue used for bonding can be an epoxy glue.

Preferably, the epoxy adhesive is of a single-component or poly-component type which can be polymerized under heat. The bonding step then comprises a step of heating to an appropriate temperature for the duration of polymerization of the adhesive.

For the production of the abrasion-resistant layer, an alloy infiltration technique is used in a stack of tungsten carbide grains. The mold used is advantageously a mold for molding walls in foundry sand bound by resins. A difficulty is then encountered because the mold comprises walls whose surface is relatively large relative to the volume of the abrasion-resistant layer to be produced, since this layer generally does not have to have a very large thickness relative to its surface. The difficulty then appears by the fact that the resin used to bind the sand of the mold tends to be consumed during infiltration, and interferes with the production of a good quality abrasion-resistant layer. To resolve this difficulty, it is necessary to adjust the quantity of resin present in the mold, to adjust it to a quantity just sufficient to maintain the foundry sand until infiltration, thus limiting the gassing resulting from the combustion of the resin. during the heating and infiltration stage. In practice, the amount of resin will be less than 6% by weight of the amount of foundry sand.

BRIEF DESCRIPTION OF THE DRAWINGS

• la figure 1 représente schématiquement en perspective un moule selon l'invention permettant de réaliser un élément de revêtement en matière antiabrasion en forme de secteur cylindrique destiné à recouvrir un substrat cylindrique ;
• les figures 2 à 5 illustrent schématiquement les différentes étapes du procédé de réalisation d'un élément de revêtement en matière antiabrasion dans un moule de la figure 1 représenté en coupe ;
• la figure 6 représente l'élément de revêtement antiabrasion ainsi obtenu ;
• les figures 7 et 8 illustrent les étapes de formage du substrat destiné à recevoir les éléments de revêtement antiabrasion ;
• la figure 9 illustre l'étape d'assemblage des éléments de revêtement antiabrasion sur le substrat de la figure 8 ;
• la figure 10 est une coupe longitudinale selon l'axe I-I de la figure 9 ;
• la figure 11 illustre l'étape de réalisation par infiltration d'un élément de revêtement antiabrasion cônique, dans un moule représenté en coupe ;
• la figure 12 illustre l'étape d'assemblage de l'élément cônique de la figure 11 sur un substrat lui-même cônique, pour réalisation d'un pointeau de vanne pour usine hydroélectrique ;
• la figure 13 illustre, en coupe longitudinale, la structure d'un pointeau de vanne selon la présente invention ; et
• les figures 14 et 15 illustrent, en coupes longitudinales selon deux plans perpendiculaires, la structure d'une dent de malaxeur selon la présente invention.

Other objects, characteristics and advantages of the present invention will emerge from the following description of particular embodiments, given in relation to the attached figures, among which:

• Figure 1 shows schematically in perspective a mold according to the invention for producing a coating member in abrasion-resistant material in the form of a cylindrical sector intended to cover a cylindrical substrate;
• Figures 2 to 5 schematically illustrate the different steps of the method of producing a coating member in abrasion-resistant material in a mold of Figure 1 shown in section;
• FIG. 6 represents the abrasion-resistant coating element thus obtained;
• Figures 7 and 8 illustrate the steps of forming the substrate for receiving the abrasion-resistant coating elements;
• Figure 9 illustrates the step of assembling the abrasion-resistant coating elements on the substrate of Figure 8;
• Figure 10 is a longitudinal section along the axis II of Figure 9;
• FIG. 11 illustrates the step of production by infiltration of a conical abrasion-resistant coating element, in a mold shown in chopped off ;
• FIG. 12 illustrates the step of assembling the conical element of FIG. 11 on a substrate itself conical, for producing a valve needle for a hydroelectric plant;
• FIG. 13 illustrates, in longitudinal section, the structure of a valve needle according to the present invention; and
• Figures 14 and 15 illustrate, in longitudinal sections along two perpendicular planes, the structure of a kneader tooth according to the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 10 and 13 to 14 illustrate the internal structure of the composite parts with abrasion-resistant coating obtained by a method according to the present invention. In all the embodiments, these parts comprise a substrate 1 covered at least in part by a layer of abrasion-resistant material 2 which is secured to it by an intermediate layer 3 of adhesive.

There is shown, in Figures 1 to 9, the successive stages of production of an abrasion-resistant part according to the invention, in an embodiment corresponding to the manufacture of a shield for aluminum mixer mixers.

Smelter mixers include a cylindrical tubular enclosure, several meters long, with a diameter of around 60 centimeters, intended to contain a carbon paste to be kneaded by kneader teeth. Some teeth are mounted fixed on the wall of the enclosure and protrude towards the inside of the enclosure, other teeth are mounted on a rotor rotating axially in the enclosure. The kneading teeth are for example as shown in longitudinal section in FIGS. 14 and 15.

In FIGS. 1 to 6, one of the coating elements made of abrasion-resistant material which will be used to cover the internal surface of the cylindrical enclosure is produced by infiltration of a binder alloy into a stack of tungsten carbide grains of mixer. In FIG. 1, a hollow mold 4 is prepared, comprising an interior recess 5 delimited by molding walls having the shape of the surface element made of abrasion-resistant material to be produced. This mold is shown empty in section in FIG. 2.

In FIG. 3, we introduce into the recess 5 of the mold 4 particles 6 of hard material such as molten tungsten carbide, vibrating the assembly, so that the surface particles come to bear against the mold walls as much as possible and are joined to each other. In FIG. 4, a sufficient quantity of an appropriate alloy 7 is prepared in suitable form, to ensure a subsequent distribution of the alloy during its subsequent melting phase. The alloy 7 is a brazing alloy capable of wetting the particles of hard material and of melting at a temperature below the melting temperature of the particles of hard material 6 and of the mold 4. In FIG. 5, the assembly is heated of the mold 4 and its content up to a temperature above the melting temperature of the alloy 7 and below the melting temperature of the hard material particles 6 and of the mold 4. This temperature is maintained for a sufficient time to ensuring the infiltration of the molten alloy 7 into the space filled with particles of hard material 6. It is then allowed to cool, and it is removed from the mold, in order to obtain the element 8 of coating made of abrasion-resistant material shown in FIG. 6.

In FIGS. 7 and 8, the substrate intended to receive the coating elements made of abrasion-resistant material is prepared. In FIG. 7, we start from a rectangular sheet 9. In FIG. 8, this rectangular sheet 9 is bent to give it a semi-cylindrical shape of suitable diameter so that, after affixing of the elements of coating made of abrasion-resistant material, the internal diameter of the assembly is in accordance with the diameter of the mixer tube to be produced.

In FIG. 9, the assembly and the attachment of the abrasion-resistant coating elements such as the element 8 are carried out on the substrate 1 such as the curved sheet metal. This attachment is effected by gluing, by applying the said abrasion-resistant coating elements 8 on the substrate 1 of curved sheet 9 with the interposition of an appropriate layer of adhesive. FIG. 10 is a longitudinal section along the axis I-I in FIG. 9, the assembly thus obtained, showing the abrasion-resistant layer 2, the substrate 1 or sheet 9 and the intermediate layer of glue 3.

In the case of a mixer for an aluminum smelter, a steel sheet 9 is advantageously used. The adhesive 3 used is an epoxy adhesive, preferably of a single-component or poly-component type which can be polymerized hot. In this case, the assembly and bonding step shown on FIG. 9 comprises a step of heating to an appropriate temperature during the polymerization time of the glue 3.

After assembly of the abrasion-resistant coating elements 8 on the substrate 1 of curved sheet metal 9, it is advantageously possible to provide for a subsequent step of machining the excess glue and the edges of the abrasion-resistant surface, in order to produce semi-cylindrical elements which can be arranged. one after the other edge-to-edge without the appearance of cracks or gaps between two adjacent elements.

Also, the mechanical resistance thus obtained from all of the abrasion-resistant elements bonded to the sheet 9 is sufficient so that the abrasion-resistant surface can be subsequently equalized during a subsequent machining step.

During the production of the abrasion-resistant coating element 8, the mold 4 used can be made of different materials. For example, one can use a graphite mold 4, previously machined to form the recess 5. A more advantageous solution consists in using a mold 4 comprising molding walls made of foundry sand bound by resins. The recess 5 is then produced by immersing a model in the mold 4 before setting the resin, and removing the model after setting the resin, according to a traditional technique in molding for the casting of metals.

However, when using such a mold 4 made of foundry sand bound by resins, a difficulty may arise from the fact that the abrasion-resistant coating element 8 to be formed has a very large surface area in relation to its volume. This is due to the fact that the covering element is generally flat. The problem that can occur is that, during infiltration, the combustion of the resin binding the sand of the mold 4 produces gas emissions which tend to seep into the recess 5 filled with hard abrasion-resistant particles 6. These gas evolution can form deposits on the particles, and, if these deposits are in excess, they can harm the wetting of the particles by the binder alloy 7 during infiltration. This then results in a poor quality of mechanical strength of the abrasion-resistant element 8 thus produced. To avoid this difficulty, the quantity of resin present in the mold 4 is adjusted to be just sufficient to maintain the foundry sand until infiltration. In practice, the amount of resin can be chosen to be less than 6% by weight of the amount of mold foundry sand 4.

In the embodiment shown in Figures 1 to 10, there is obtained a composite part, shown in Figure 9, comprising a sheet metal substrate 1 9 of semi-cylindrical steel shape, with, on the inner surface of the half-cylinder , a layer of polymerized neck adhering to the half-cylinder and, adhering to the layer of polymerized glue and surmounting it, a paving of plates or abrasion-resistant coating elements 8 in the form of a sector of cylinder with generally rectangular outline, the paving according to the curvature of the inner surface of the half-cylinder, the assembly forming a shielding plate for an aluminum mixer.

In the embodiments shown in Figures 13 to 15, the composite part obtained by the method of the invention comprises a steel substrate 1 having a generally convex shape. On the exterior surface of the substrate, there is a layer of polymerized adhesive 3. Overlying said layer of glue 3, there is a cap 2 made of abrasion-resistant material.

Figures 11 to 13 relate to the production of a needle valve needle used in hydroelectric plants. Such a needle is of conical shape, and comprises a conical substrate 1 of steel whose conical outer surface is covered with a conical cap 2 forming an element made of abrasion-resistant material. As in the embodiment of FIGS. 1 to 10, the substrate 1 and the cap 2 are produced separately. The cap 2 is itself produced by infiltration, as shown diagrammatically in FIG. 11, in a mold 4 comprising a removable core. 40, the mold 4 forming the outer surface of the cap, the core 40 forming the inner surface of the conical cap. After demolding, the cap 2 is adapted on the substrate 1, as shown in FIG. 12, with the interposition of a layer of glue, and the needle is obtained as shown in section in FIG. 13, presenting the cap 2 , the substrate 1 and the intermediate layer of adhesive 3.

The embodiment of FIGS. 14 and 15 relates to the production of an aluminum blender tooth. Note in these figures, the substrate 1, the cap 2 forming an abrasion-resistant coating element, and the intermediate layer 3 of adhesive. The part must advantageously have the shape shown in the figures. This part is formed according to a process similar to that described in relation to the previous figures, by separately producing the substrate 1 and the cap 2, the cap 2 being obtained by infiltration in a mold.

The assembly of the substrate and the cap by gluing, in all the embodiments of the invention, allows the intermediate adhesive 3 to act as a damper between the substrate 1 and the abrasion-resistant element 2. It increases considerably the apparent mechanical resistance of the abrasion-resistant coating thus produced, so that subsequent re-machining of its surface is made possible. The part has a significantly improved impact resistance compared to production techniques by overmolding infiltration.

In addition, this technique according to the present invention avoids heating the substrate 1, so that one does not alter its external appearance. On the other hand, in the known techniques of infiltration during overmolding, the heating of the substrate 1, when it is made of steel, causes an alteration of its surface and requires re-machining.

It is understood that the production of partial covering elements, as shown in FIG. 9, makes it possible to produce these elements while reducing the risk of scrap. Indeed, if an element is defective, it suffices to replace it with another, without having to redo the entire coating.

The present invention is not limited to the embodiments which have been explicitly described, but it includes the various variants and generalizations thereof contained in the field of claims below.

Claims (15)

1. Method of manufacturing a composite part with an antiabrasion coating, said part including at least a substrate (1) covered with a layer of antiabrasion material (2) based on grains of tungsten carbide, said method comprising the following steps :

   a) producing a steel substrate (1) whose generally convex shape and surface condition are appropriate to having glued thereto covering members (2) of antiabrasion material based on grains of tungsten carbide,

   b) infiltrating a binder alloy (7) into a heap of grains of tungsten carbide (6) to make one or more antiabrasion material covering members (2, 8) having a concave inside surface shaped to match the convex surface of the substrate (1) and an outside surface shaped to constitute the antiabrasion surface of the composite part to be made,

   c) gluing the antiabrasion material covering member or members (8) to the substrate by applying said covering members (8) to the convex surface of the substrate (1) with an appropriate layer of glue (3) between them.
2. Method of manufacturing an aluminium works grinder lining plate with an antiabrasion coating, said plate including at least a substrate (1) covered with a layer of antiabrasion material (2) based on grains of tungsten carbide, said method comprising the following steps:

   a) producing a semicylindrical curved plate substrate (1) whose inside surface condition is appropriate to having glued thereto covering members (2) of antiabrasion material based on grains of tungsten carbide,

   b) infiltrating a binder alloy (7) into a heap of grains of tungsten carbide (6) to make a plurality of antiabrasion material covering members (2, 8) having an inside surface shaped to match the inside surface of the substrate (1) and an outside surface shaped to constitute the antiabrasion surface of the lining plate to be made,

   c) gluing the antiabrasion material covering members (8) to the substrate by applying said covering members (8) to the inside surface of the substrate (1) with an appropriate layer of glue (3) between them, producing a lining of antiabrasion material plates following the curvature of the inside surface of the half-cylinder.
3. Method according to claim 1 or claim 2 characterised in that:

   - the substrate (1) is steel,

   - the glue (3) is an epoxy glue.
4. Method according to claim 3 characterised in that:

   - the epoxy glue (3) is of a single-component or multi-component type polymerised by heating,

   - the gluing step comprises a step of heating to an appropriate temperature during polymerisation of the glue (3).
5. Method according to any one of claims 1 to 4 characterised in that it comprises a subsequent step of machining excess glue and the edges of the antiabrasion surface.
6. Method according to any one of claims 1 to 5 characterised in that it comprises a later step of machining the antiabrasion surface.
7. Method according to any one of claims 1 to 6 characterised in that it comprises a previous step of manufacturing an antiabrasion material surface member (8) in which:

   - hollow mould means (4) comprising an interior cavity (5) delimited by moulding walls having the shape of the antiabrasion material surface member to be made are prepared,

   - hard material such as tungsten carbide particles (6) are introduced into the cavity (5) of the mould (4), using vibration so that the particles at the surface are applied optimally to the walls of the mould and are contiguous with each other,

   - a sufficient quantity of an appropriate alloy (7) is prepared in a form suitable for subsequent distribution of the alloy during the subsequent phase of melting it, the alloy being a brazing alloy adapted to wet the hard material particles (6) and to melt at a temperature lower than the melting point of the hard material particles (6) and the mould (4),

   - the temperature is raised to a temperature higher than the melting point of the alloy (7) and lower than the melting point of the hard material particles (6) and the mould (4),

   - this temperature is maintained for a sufficient duration for infiltration of the molten alloy (7) into the cavity (5) filled with hard material particles (6),

   - the antiabrasion surface member is removed from the mould after cooling.
8. Method according to claim 7 characterised in that the mould means (4) comprise resin bonded casting sand moulding walls.
9. Method according to claim 8 characterised in that the quantity of resin present in the mould means (4) is made just sufficient to retain the casting sand until the infiltration step, reducing generation of gas resulting from combustion of the resin during the heating and infiltration step.
10. Method according to claim 9 characterised in that the quantity of resin is less than 6% by weight of the quantity of casting sand.
11. Composite part with an antiabrasion coating made by the method according to claim 2 characterised in that it comprises:

    - a semicylindrical substrate (1) made from curved plate (9),

    - a layer of polymerised glue (3) on the inside surface of and adhering to the half-cylinder,

    - adhering to the layer of polymerised glue (3) and on top of it a lining of plates (8) of antiabrasion material based on tungsten carbide, said lining following the curvature of the inside surface of the half-cylinder,

    - the whole forming a lining plate for an aluminium works grinder.
12. Composite part with an antiabrasion coating according to claim 11 characterised in that the plates (8) are cylindrical sector shape with a generally rectangular contour.
13. Composite part with an antiabrasion coating made by the method according to claim 1 characterised in that it comprises:

    - a generally convex steel substrate (1),

    - a layer of polymerised glue (3) on the convex outside surface of the substrate (1),

    - a cap (2) of antiabrasion material based on tungsten carbide adhering to said layer of polymerised glue (3) whose inside surface is shaped to conform to the convex outside surface of the substrate (1).
14. Composite part with an antiabrasion coating according to claim 13 characterised in that it constitutes an aluminium works grinder tooth.
15. Composite part with an antiabrasion coating according to claim 13 characterised in that it has a generally conical shape and constitutes a nozzle valve needle.

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