WO2005000503A1

WO2005000503A1 - Method for producing reinforced metal components

Info

Publication number: WO2005000503A1
Application number: PCT/FI2004/000409
Authority: WO
Inventors: Jari Ilmari Liimatainen
Original assignee: Metso Powdermet Oy
Priority date: 2003-06-30
Filing date: 2004-06-30
Publication date: 2005-01-06
Also published as: FI20030978A; FI20030978A0

Abstract

A method for producing multi-material components, as wall as a multi-material component, said material including tough metallic material (B) and wear resistant material (A). In the method, a seed-blank is produced, into which pieces of material are placed, after which atomized material will be sprayformed around and onto the solid materials.

Description

METHOD FOR PRODUCING REINFORCED METAL COMPONENTS

The present invention relates to manufacturing a multi-material component being formed by a plurality of different materials, at least one of those being metal. More precisely, the invention relates to manufacturing a multi-material component by sprayforming, eventu- ally by connecting hot-isostatic pressing and/or hot working methods to the manufacturing.

Background of the Invention

In the development of wear-resisting materials it is typically difficult to combine the wear- resistance and an adequate mechanical reliability, especially toughness. For increasing the wear-resistance, it is typical to try to increase the hardness by alloying, heat treatments and work hardening. In addition, ceramic carbide components, nitrides and carbo-nitrides or other especially hard particles increasing the wear resistance are often added to the material in order to increase the wear resistance. Increase of the hardness and adding hard particles to the structure decrease the toughness of the material and increase the risk of fractures and spallings caused by the service loads.

If the wear resistance/toughness combination achieved with a monolithic, single material is not sufficient, it has been typically tried to produce different types of coatings and combined structures, where only the wearing part of the article locally includes material with good wear resistance but more fragility. Thereby the fracture of the wear resistant material does not cause the obsolescence of the whole article or danger to the equipment, process or the operating people. Spalling, however, naturally speeds up the wearing prominently compared with the normal abrasive and erosion wearing. Typical methods for producing composite constructions are deposition welding, soldering, casting arid mechanical fittings like shrink fits.

In certain circumstances it is, however, necessary to limit the loosing of material from the component caused by especially hard service loads and impacts. This type of applications are among others hammer mills, grinding mills, disintegrators and hogging mills, where the load frequency is so high, that if the wearing changes into spalling, the material loss of the wear resistant material happens too quickly.

Some methods for effecting to the erosion rate in a situation described above are to use for the coating small wearing parts that are soldered or glued onto the wearing area of the ba- sic material. This kind of a method, however, is expensive and requires a lot of preparing. Same problems are connected with the mechanical joints; the preparing of the pieces to be connected and their connecting is expensive and increases significantly the manufacturing costs.

Description of the Invention

In the method in accordance with the invention, the material is produced so that the structure comprises microscopically wear resistant, hard material (A) and tough, mechanically resistant material (B). The material (B) improving the toughness has been placed into the wear resistant material so, that with respect to the service loads a maximal advantage can be gained or, on the other hand, the influence decreasing the wear resistance has been minimized.

In the alternative, where the tough, mechanically resistant material (B) has been placed into the multi-material component so, that its task is to limit the size of pieces loosing from the surface of the component in especially hard load situations and to prevent macroscopic, catastrophic breakages, the material (B) can be in the structure as fiber, plate or as that kind of a honeycomb structure, that surrounds the areas made of the hard material (A). The fiber-like structures (B) prevent loosing of the hard material (A) if it breaks and bind it into the structure for as long time as possible. The honeycomb structures act in the same way and, in addition, they limit the size of the biggest loosing piece better than the fiber strac- ture. When using plate-like constructions, the orientation of the service loads must be known exactly in order to prevent the breaking of the hard material in longitudinal direction between the tough plate materials or along junctions.

In the other alternative, the structure of the multi-material component is formed so that the hard, wear resistant material (A) is placed into the structure as fibers, plates or as a honey- comb structure surrounded by a tough, mechanically resistant material (B). Thereby the hard material (A) slows the wearing of the component.

By means of a wear part material in accordance with the present invention, a better combination of the wear resistance and toughness can be achieved than by using only purely wear resistant material. Additionally, by choice of the materials (A) and (B) and by their size distribution, a desired combination of wear resistance and toughness can be provided for different applications and the spalling and wearing properties of the wearing part can be influenced.

More precisely, the method in accordance with the invention is characterized by what has been stated in the characterizing part of claim 1, and the component in accordance with the invention is characterized by what has been stated in the characterizing part of claim 7.

The invention will be described in more detail in the following, with reference to the enclosed drawings, wherein

Figure 1 shows one example of a seed-plate used in the method in accordance with the invention, and solid pieces attached thereto, and

Figure 2 shows a multi-material component blank produced by sprayforming a seed- plate and solid pieces according to figure 1.

The method in accordance with the invention includes the following steps:

I. Producing for sprayforming a so-called seed-plate of metal, said plate enduring the heat and mechanical loads during the sprayforming, solid materi- als to be attached thereto, around or on top of which the sprayforming will be produced. The materials to be placed into the seed-plate are chosen based on the requirements for the specific properties set on the material.

II. Producing a molten metal, of which powder is atomized onto the solid materials placed onto the seed-plate so that the powder to be atomized together with the solid materials forms a blank having a desired shape and distribution of the materials in the blank.

The example shown in figure 1 has a seed-plate 1, where solid pieces are attached to, in this embodiment round rods 2 of tough metallic material (B). Hard, wear resistant material (B) is sprayformed onto the pre-blank formed by the seed-plate 1 and the rods 2. In the sprayforming, the molten metal is led from the melt through special nozzles to the atomizing chamber, where the molten metal is resolved into small, partly molten metal particles and collected onto the seed-material. The metal particles, often still partly molten, colliding with the seed-material, attach to each other thus forming a layer of material solidifying on the surface and around the seed-material and being essentially compact.

Figure 2 shows a multi-material blank after the sprayforming, in which the pieces 2 are inside the sprayformed material 3. The seed-plate can be removed after the sprayform- ing or it can remain as a part of the component, if necessary. The produced blank is already suitable to be used in some applications as such.

The blank produced with a method of the present invention can be furtlier processed, if desired, with pressure and/or temperature for example to more compact or for improving the bond between the materials A and B, for example by hot working (hot- hammering, hot rolling) or by hot-isostatic pressing.

The produced blanks can, if necessary, be treated with different finishing processes, like machining and heat treatments, according to the requirements set on the materials being used.

The finished wear resistant material can also be attached, if necessary, to another com- ponent or sub-assembly for example by soldering, with a mechanical joint, by gluing or by welding it into a desired place in the component or the sub-assembly.

As well the wear resistant, more brittle material (A) as the softer, tough material (B) can be either solid materials attached to the seed-plate or materials to be sprayformed on or around them.

The size and number of the solid materials to be placed on the seed-plate in the first step of the method in accordance with the invention is chosen so that after the working its size distribution is suitable with respect to the requirements of the object. For example in the demanding usages, in which hard, impact loads are exerted to the component, it is important that the tough portion of the structure is able to prevent the microscopic fractures. When choosing the material, in addition, it must be taken into account, that the parameters used for producing the different materials (compacting, hot forming, heat treatment) are suitable for both of the materials. Also too brittle microstructures must not be formed into the junctions of the materials, whereby especially the cracking of the more wear resistant and more brittle material out of the material during the ser- vice load, thus decreasing the toughness of the multi-material component, can be pre- vented. This is especially disadvantageous, if plate-like toughening materials (B) are used in the seed-plate and the load orientation makes it possible that the cracking can occur along the junction between the material (A) and (B). Additionally, the coefficients of thermal expansion of the materials (A) and (B) must not differ too much from each other, because in that case high residual stresses are formed between the material

(A) and (B) in the structure of the component, which can increase the inclination to spalling or promote formation of fatigue breakages.

Solid material can be placed into the seed-plate as a rod, plate or honeycomb structure, depending on the distribution of the microstructure, which is desired after the hot work- ing.

In the sprayforming process of the invention metal is atomized of material, which is first molten, alloyed and superheated in a melting tank, whereas in the known thermal spraying processes (like flame spraying, voltaic arc spraying, plasma spraying, powder plasma spraying and HVOF-process) the principle is that the metallic and/or ceramic and in some cases polymer material having a banded structure are totally or partly molten in the gas flame or plasma arc into the melting point or close to that and transported in gas flowing with a high speed onto the surface of the component to be coated, on which the almost or totally molten drops attach to the surface and to each other, simultaneously solidifying into a solid layer.

Also a solid basic material like forging or casting can be used in the sprayforming, onto which the solid materials to be left inside the sprayed layer will be placed. Thereby the sprayed layer with the solid material to be left inside forms an own separate area on the surface of the solid basic material or around it.

The material to be sprayformed can either be metallic powder or a mixture of different metallic and/or ceramic powders, by means of which the target properties in the desired object can be achieved. The ceramic and/or metallic powder can be injected into the at- omization spray, whereby it will be distributed to the sprayformed material in the desired way.

The material can further be processed after the sprayforming for example by hot work- ing or hot-isostatic pressing for example for making it more compact or for improving the bond between the material (A) and (B). Among others, hot rolling, radial forging or open forging can be used as hot working method. By choosing the reduction of the hot working the distribution of the materials (A) and (B) can be influenced.

When connecting the multi-material produced by the method of the invention and hot worked for producing a wear resistant component, blanks will be separated from the multi-material to be attached to the component and required finishing will be performed before connecting. In certain cases the pieces forming the component can be attached to each other by welding or hot-isostatic pressing and after connection for example the heat treatment of the whole product will be performed.

In the method and multi-material component in accordance with the invention the tough material (B) is preferably metallic, iron-based material having an iron content of more than 50 weight percent.

The material in accordance with the invention is suitable to be used in components having especially hard loadings, among other things in the wearing parts of rock crashers, linings of grinding mills, hammer mills, disintegrators.

Claims

1. A method for manufacturing multi-material components, said material including tough metallic material (B) with a desired distribution with a hard, wear resistant material (A), said wear resistant material (A) being martensitic tool steel including 5 volume percent of carbides of MC-type (VC, TiC, NbC), characterized in, that basic material acting as a seed-blank is produced,

- solid material pieces are placed onto the seed-blank in a desired way,

- atomized material is sprayformed around and onto the solid materials so that a blank having a desired shape will be formed.

2. A method in accordance with claim 1, characterized in, that the material to be sprayformed is of tough metallic material (A).

3. A method in accordance with claim 1, characterized in, that the material to be sprayformed is of hard, wear resistant material (B).

4. A method in accordance with any of the claims from 1 to 3, characterized in, that after the sprayforming the blank is hot worked or pressed by hot-isostatic pressing.

5. A method in accordance with any of the claims from 1 to 4, characterized in, that the tough metallic material (B) is of metallic, iron-based material (Fe > 50 weight percent).

6. A method in accordance with any of the claims from 1 to 5, characterized in, that ceramic particles (for example carbides, nitrides or oxides), are injected into the metallic spray to be sprayformed, in which the portion of the metallic bond material is maximum 30 weight percent, or metal particles.

7. A multi-material component manufactured with the method in accordance with any of the claims from 1 to 6, comprising tough iron based (Fe > 50 weight percent) material (B) and wear resistant material (A), characterized in, that - the tough material (B) forms maximum approximately 50 percent, preferably 10-20 % of the cross sectional surface of the finished material

- hardness of the hard material (A) when heat treated is minimum HRC 40.

8. A multi-material component in accordance with claim 7, characterized in, that the volumetric proportion of the tough material (B) in the component is 20-40 volume percentages.