JP7168491B2 - zygote - Google Patents

Description

TECHNICAL FIELD The present invention relates to a joined body formed by forming a metal film on a base material, and a method for manufacturing the joined body.

BACKGROUND ART In recent years, it has been studied to increase the strength and hardness of parts such as automobile panels, tubular members, and rod-shaped members to improve wear resistance. For example, as a material used for this part, an iron-based material is used as a base material, and a metal material made of at least one of nickel, cobalt, chromium, and molybdenum is sprayed to the base material to form a thermal spray coating, and a laser beam is applied to the base material. A material is known in which an alloy layer is formed by melting a base material and a thermal spray coating by irradiating with (see, for example, Patent Document 1).

Japanese Patent No. 3015816

By the way, in recent years, replacement of iron-based materials with aluminum-based materials has been studied for the purpose of reducing the weight of various parts in automobile applications. While aluminum-based materials are suitable for weight reduction, it is difficult to obtain sufficient product strength if all aluminum-based materials are used. Therefore, replacement of some iron-based materials with aluminum-based materials is being studied. In particular, parts that cause friction with other parts are required to have increased strength and hardness to impart wear resistance.

SUMMARY OF THE INVENTION The present invention has been made in view of the above, and an object of the present invention is to provide a joined body and a method for manufacturing the joined body, which can have high strength and hardness and can be reduced in weight.

In order to solve the above-described problems and achieve the object, the joined body according to the present invention includes a base material containing aluminum or an aluminum alloy as a main component and a metal coating containing iron as a main component and carbon as an essential additive. a metal coating laminated to and bonded to the substrate, the metal coating forming a surface opposite to the substrate and comprising cementite and martensite a first hard layer, a heat affected zone having a lower hardness than the hardness of the first hard layer and made of ferrite, martensite and retained austenite, and between the first hard layer and the heat affected zone and a second hard layer comprising martensite and retained austenite.

Further, in the joined body according to the present invention, in the above invention, the first hard layer has a Vickers hardness of Hv600 or more, and the heat affected zone has a Vickers hardness of Hv200 or more and Hv400 or less. and

Further, in the joined body according to the present invention, in the above invention, the metal film further includes a selective additive material containing at least one of copper, molybdenum, chromium, nickel and manganese.

In addition, a method for manufacturing a bonded body according to the present invention is a method for manufacturing a bonded body in which a coating film formed by using material powder is laminated on the surface of a base material containing aluminum or an aluminum alloy as a main component, and is mainly composed of iron. A pretreatment film forming step of accelerating the material powder as a component together with gas and spraying it onto the surface of the substrate in a solid phase state to form a pretreatment film on the surface of the substrate; a coating step of applying carbon; and a coating forming step of applying a quenching treatment to the surface of the pretreatment coating coated with carbon to form a metal coating.

Further, in the method for manufacturing a bonded body according to the present invention, in the above invention, the pretreatment film forming step includes spraying the material powder containing iron as a main component and carbon as an essential additive onto the surface of the base material. It is characterized by

ADVANTAGE OF THE INVENTION According to this invention, it is effective in being able to reduce weight, having high intensity|strength and hardness.

FIG. 1 is a cross-sectional view showing the structure of a joined body according to one embodiment of the present invention. FIG. 2 is a partial cross-sectional view enlarging a part of the joined body shown in FIG. FIG. 3 is a flow chart illustrating a method for manufacturing a joined body according to one embodiment of the present invention. FIG. 4 is a diagram for explaining a method of manufacturing a joined body according to one embodiment of the present invention. FIG. 5 is a diagram illustrating a method of manufacturing a joined body according to one embodiment of the present invention. FIG. 6 is a schematic diagram showing an overview of a cold spray apparatus used for forming a metal film on a joined body according to one embodiment of the present invention. FIG. 7 is a diagram showing an example of material powder used for manufacturing a joined body according to one embodiment of the present invention. FIG. 8 is a diagram showing an example of material powder used for manufacturing a joined body according to one embodiment of the present invention. FIG. 9 is a diagram showing an example of material powder used for manufacturing a joined body according to one embodiment of the present invention. 10A and 10B are diagrams illustrating a method for manufacturing a joined body according to an embodiment of the present invention. FIG. 11 is a diagram showing a cross-sectional image of Example 1. FIG. FIG. 12 is a diagram showing a cross-sectional image of Example 2. FIG. FIG. 13 is a diagram showing a cross-sectional image of Example 3. FIG. FIG. 14 is a diagram showing a cross-sectional image of Example 4. FIG. 15 is a diagram showing a cross-sectional image of Comparative Example 1. FIG. 16 is a diagram showing a cross-sectional image of Comparative Example 2. FIG. 17 is a diagram showing a cross-sectional image of Comparative Example 3. FIG. 18 is a diagram showing a cross-sectional image of Comparative Example 4. FIG. 19 is a diagram showing a cross-sectional image of Comparative Example 5. FIG. 20 is a diagram showing a cross-sectional image of Comparative Example 6. FIG. 21 is a diagram showing the EBSD analysis results of the conjugate according to Example 1. FIG. 22 is a diagram showing the EBSD analysis results of the conjugate according to Example 3. FIG. 23 is a diagram showing the EBSD analysis results of the conjugate according to Comparative Example 2. FIG. 24 is a diagram showing hardness measurement results of Example 1. FIG. 25 is a diagram showing hardness measurement results of Example 2. FIG. 26 is a diagram showing hardness measurement results of Example 3. FIG. 27 is a diagram showing hardness measurement results of Example 4. FIG. 28 is a diagram showing hardness measurement results of Comparative Example 1. FIG. 29 is a diagram showing hardness measurement results of Comparative Example 2. FIG. 30 is a diagram showing hardness measurement results of Comparative Example 3. FIG. 31 is a diagram showing hardness measurement results of Comparative Example 4. FIG.

Hereinafter, the form for carrying out the present invention is explained in detail with a drawing. In addition, the present invention is not limited by the following embodiments. In addition, each drawing referred to in the following description only schematically shows the shape, size, and positional relationship to the extent that the contents of the present invention can be understood. That is, the present invention is not limited only to the shapes, sizes, and positional relationships illustrated in each drawing.

FIG. 1 is a cross-sectional view showing the structure of a joined body according to one embodiment of the present invention. FIG. 2 is a partial cross-sectional view enlarging a part of the joined body shown in FIG. A joined body 1 shown in FIG. 1 includes a substrate 10 and a metal coating 20 formed on one surface of the substrate 10 .

The base material 10 is a substantially plate-shaped member made of aluminum or an aluminum alloy containing aluminum as a main component.

The metal film 20 is made of a material powder containing soft pure iron (Fe) as a main component and essential additives. An essential additive is carbon (C).
Also, the metal coating 20 may further include optional additives. The selective additive is at least one of copper (Cu), molybdenum (Mo), chromium (Cr), nickel (Ni) and manganese (Mn).
The metal film 20 is formed by spraying a powder of a material containing at least the main component described above by a cold spray method, which will be described later.

The metal film 20 is mainly composed of martensite with high density on the surface opposite to the substrate 10 side, and is mainly composed of ferrite with low density on the substrate 10 side. The metal film 20 is multi-layered. Specifically, the metal coating 20 consists of a first hard layer 21, a second hard layer 22, a heat affected zone 23, and a non-heat affected zone 24 from the side opposite to the substrate 10. As shown in FIG.

Also, the metal film 20 has a dense structure by quenching the surface of the film formed by the cold spray method. A laser, for example, is used for the hardening treatment. The layers densified by the quenching process correspond to the first hard layer 21, the second hard layer 22, and the heat-affected zone 23, and are hard layers formed of cementite, martensite, and retained austenite. On the other hand, the layer that is not quenched corresponds to the non-heat-affected zone 24 and has a loose structure of ferrite layers.

The first hard layer 21 is composed of cementite, which is a structure of iron carbide (Fe3C: iron carbide), and martensite, which is a structure of α′ iron. The first hard layer 21 has a Vickers hardness of Hv600 or higher.

The second hard layer 22 is composed of martensite, which is a structure of α′-iron, and retained austenite, which is a structure in which other elements such as carbon and alloying elements are dissolved in γ-iron. The second hard layer 22 has a Vickers hardness of Hv300 or higher.

The heat-affected zone 23 is composed of ferrite, which is a structure of α-iron, martensite, which is a structure of α′-iron, and retained austenite, which is a structure in which other elements such as carbon and alloy elements are dissolved in γ-iron. Become. The heat affected zone 23 has a Vickers hardness of Hv 200 or more.

The non-heat-affected zone 24 is made of ferrite, which is an α-iron structure. The non-heat-affected zone 24 has a Vickers hardness of Hv80 or higher.

Next, a method for manufacturing the joined body 1 will be described with reference to FIGS. 3 to 10. FIG. FIG. 3 is a flow chart illustrating a method for manufacturing a joined body according to one embodiment of the present invention. 4 and 5 are diagrams illustrating a method of manufacturing a joined body according to an embodiment of the present invention. FIG. 6 is a schematic diagram showing an overview of a cold spray apparatus used for forming a metal film on a joined body according to one embodiment of the present invention.

First, the substrate 10 described above is prepared (see FIG. 4).
A powder of a material for forming the metal film 20 is accelerated with gas onto the substrate 10 by a cold spray device 30 shown in FIG. A pre-heat treatment film 200 is formed (step S101: see FIG. 5).

The cold spray device 30 includes a gas heater 31 that heats the compressed gas, a powder feeder 32 that contains the powder of the material for forming the metal coating 20 and supplies it to the spray gun 33, the heated compressed gas and It is equipped with a gas nozzle 34 for injecting the material powder supplied therein to the substrate, and valves 35 and 36 for adjusting the amount of compressed gas supplied to the gas heater 31 and the powder supply device 32, respectively.

The material for forming the metal film 20 is a powder containing soft pure iron (Fe), which is the main component of the metal film 20, and the above-described essential additive and optional additive. When the essential additive is applied after film formation, the powder may not contain the essential additive. On the other hand, if the essential additive is not applied after film formation, the powder contains the essential additive.

7 to 9 are diagrams showing examples of material powders used for manufacturing a joined body according to one embodiment of the present invention. Material powders include, for example, base powders, essential additives, and optional additives. The base powder 100 is powder made of pure iron (see FIG. 7). The essential additive is a powder made of carbon. Also, the selective additive is at least one of copper (Cu), molybdenum (Mo), chromium (Cr), nickel (Ni) and manganese (Mn). Note that cast iron or high-speed steel may be used as the iron material containing carbon.

Specifically, the powder material includes a pre-sintered powder or mixed powder containing a base powder and essential additives, a pre-sintered powder or mixed powder containing a base powder and selective additives, a base powder, essential additives and Pre-sintered powders or mixed powders containing selected additives. For example, the preliminary sintered powder 110 shown in FIG. 8 has an essential additive 111 and optional additives 112 and 113 adhered to the base powder 100 . On the other hand, in the mixed powder, like the mixed powder 120 shown in FIG. 9, the base powder 100, the essential additive 111, and the selective additives 112 and 113 are not fixed and can move freely.

Helium, nitrogen, air, or the like is used as the compressed gas. The compressed gas supplied to the gas heater 31 is, for example, 50° C. or higher and is heated to a temperature in the range lower than the melting point of the powder of the material for forming the metal film 20, and then supplied to the spray gun 33. be done. The heating temperature of the compressed gas is preferably 300°C or higher and 900°C or lower. On the other hand, the compressed gas supplied to the powder supply device 32 supplies the powder in the powder supply device 32 to the spray gun 33 in a predetermined discharge amount.

The heated compressed gas is made into a supersonic flow (approximately 340 m/s or more) by a diverging gas nozzle 34 . The gas pressure of the compressed gas at this time is preferably about 1 to 5 MPa. This is because the adhesion strength of the metal film 20 to the substrate 10 can be improved by adjusting the pressure of the compressed gas to this level. More preferably, the treatment should be performed at a pressure of about 5 MPa. The powder of the material supplied to the spray gun 33 is accelerated by being introduced into the supersonic flow of this compressed gas, and collides with the substrate 10 at high speed while remaining in a solid phase state to deposit, forming a pretreatment film 200. (see FIG. 5). It should be noted that the apparatus is not limited to the cold spray apparatus 30 shown in FIG. 6 as long as the apparatus can collide the material powder toward the substrate 10 in a solid state to form a coating.

The pretreatment film 200 formed by the cold spray apparatus 30 described above contains a main component (iron), essential additives and selective additives. In this pretreatment coating 200, the selective additive acts as a sintering aid that assists hardenability. Therefore, the pretreatment film 200 has a high density and is softer than the metal film 20 . The pretreatment film 200 preferably has a Vickers hardness of Hv500 or less, for example.

After the pretreatment film 200 is formed, the surface is cut into a desired shape (step S102: pretreatment film surface processing step). At this time, since the pretreatment film is a soft film that is only work-hardened due to an increase in dislocation density, it can be easily cut. Thereafter, carbon is applied to the pretreatment film 200 in order to improve hardenability (step S103: carbon application step).

Thereafter, the surface of the pretreatment film 200 is hardened by high frequency or laser (step S104: hardening treatment step). 10A and 10B are diagrams illustrating a method for manufacturing a joined body according to an embodiment of the present invention. FIG. For example, as shown in FIG. 10, by irradiating the surface of the pretreatment film 200 with a laser L and performing a quenching treatment, the above-described first hard layer 21, second hard layer 22, heat-affected zone 23, non A metal film 20 consisting of a heat affected zone 24 is formed.
A high frequency wave may be used instead of the laser.

In the above-described embodiment, the powder of the material for forming the metal coating 20, which contains the main component made of iron, the essential additive made of carbon, and the selective additive, is mixed with gas. The pretreatment film 200 is formed by spraying and depositing it on the surface of the substrate 10 in a solid state, and after surface cutting, the surface of the pretreatment film 200 is subjected to heat treatment. According to the above-described embodiment, the metal film 20 having a hard layer on the surface side is formed on the base material 10 made of aluminum or an aluminum alloy. You can get 1 body.

Moreover, according to the above-described embodiment, the metal coating 20 having a hard layer on the surface side and a soft layer on the substrate 10 side is formed, so that the metal coating 20 having high toughness can be obtained. Therefore, the metal film 20 having high strength against external load can be obtained.

Further, according to the above-described embodiment, the surface processing is performed in the state of the relatively soft film before quenching treatment, so that the shape of the metal film 20 can be easily processed.

In the above-described embodiment, an example in which quenching treatment is performed after applying carbon to the pretreatment film has been described. may

In this way, the present invention can include various embodiments and the like not described here, and various design changes and the like can be made within the scope of the technical idea specified by the claims. It is possible.

Examples of the joined body according to the present invention will be described below. However, the present invention is not limited to these examples.

(Example 1)
An aluminum alloy (A6063-T6) having a thickness of 50 mm and a thickness of 10 mm was used for the base material 10 .
As the powder material for forming the metal film, α-iron (αFe: ABC manufactured by Höganäs) having a particle size of 150 μm, which is a base powder, was used.
This powder material was sprayed onto the base material 10 using the cold spray apparatus described above to form a pretreatment film, and after cutting, the pretreatment film was coated with carbon and quenched with a laser.
Nitrogen was used as the working gas, the gas pressure was set to 5 MPa, and the gas temperature was set to 800° C. in the film formation treatment using the cold spray apparatus.
After that, carbon (essential additive) was applied to the surface of the formed film, and quenching treatment was performed.
In the hardening process, a semiconductor laser having an irradiation range of 6 mm (rectangular) and an irradiation pass of 1 was used as a laser oscillator. The output of the laser was set to 1250 W, the temperature of the hardening treatment was set to 1600° C., and the working speed, which is the moving speed of the laser, was set to 200 mm/min. Here, the quenching temperature is the target temperature (target temperature) of the temperature of the pretreatment film heated by laser irradiation.
Each internal layer of the metal film after quenching treatment was confirmed by a cross-sectional image.
Table 1 shows the composition of the metal film of Example 1 and the layers formed.

(Example 2)
A metal film was formed in the same manner as in Example 1, except that the powder material for forming the metal film was obtained by adding the essential additive (carbon) and the optional additive to the base powder described above. Carbon (C: UF4 manufactured by Höganäs) with a particle size of 25 μm was used as an essential additive. Copper (Cu: Distaloy ACu manufactured by Höganäs) with a particle size of 25 μm was used as the selective additive. In the material powder, carbon is adjusted so that the volume content of the final material powder is 2%. Also, copper is adjusted so that the volume content of the final material powder is 2%.
Table 1 shows the composition of the metal coating of Example 2 and the layers formed.

(Example 3)
A metal film was formed in the same manner as in Example 1, except that the powder material for forming the metal film was obtained by adding the essential additive (carbon) and the optional additive to the base powder described above. Carbon (C: UF4 manufactured by Höganäs) with a particle size of 25 μm was used as an essential additive. Copper (Cu: Distaloy ACu manufactured by Höganäs) with a particle size of 25 μm was used as the selective additive. In the material powder, carbon is adjusted so that the volume content of the final material powder is 7%. Also, copper is adjusted so that the volume content of the final material powder is 2%.
Table 1 shows the composition of the metal coating of Example 3 and the layers formed.

(Example 4)
A metal film was formed in the same manner as in Example 1, except that the powder material for forming the metal film was obtained by adding essential additives and optional additives to the base powder described above. Carbon (C: UF4 manufactured by Höganäs) with a particle size of 25 μm was used as an essential additive. Copper (Cu: Distaloy ACu manufactured by Höganäs) with a particle size of 25 μm was used as the selective additive. In the material powder, carbon is adjusted so that the volume content of the final material powder is 12%. Also, copper is adjusted so that the volume content of the final material powder is 2%.
Table 1 shows the composition of the metal coating of Example 4 and the layers formed.

(Comparative example 1)
A metal film was formed in the same manner as in Example 1, except that the pretreatment film after cutting was not coated with carbon and was quenched by a laser.
Table 1 shows the composition of the metal film of Comparative Example 1 and the layers formed.

(Comparative example 2)
As the powder material for forming the metal film, the above-mentioned base powder to which essential additives and optional additives are added is used, and the pretreatment film after cutting is quenched by laser without applying carbon. A metal film was formed in the same manner as in Example 1, except that the treatment was performed. Carbon (C: UF4 manufactured by Höganäs) with a particle size of 25 μm was used as an essential additive. Copper (Cu: Distaloy ACu manufactured by Höganäs) with a particle size of 25 μm was used as the selective additive. In the material powder, carbon is adjusted so that the volume content of the final material powder is 2%. Also, copper is adjusted so that the volume content of the final material powder is 2%.
Table 1 shows the composition of the metal film of Comparative Example 2 and the layers formed.

(Comparative Example 3)
As the powder material for forming the metal film, the above-mentioned base powder to which essential additives and optional additives are added is used, and the pretreatment film after cutting is quenched by laser without applying carbon. A metal film was formed in the same manner as in Example 1, except that the treatment was performed. Carbon (C: UF4 manufactured by Höganäs) with a particle size of 25 μm was used as an essential additive. Copper (Cu: Distaloy ACu manufactured by Höganäs) with a particle size of 25 μm was used as the selective additive. In the material powder, carbon is adjusted so that the volume content of the final material powder is 7%. Also, copper is adjusted so that the volume content of the final material powder is 2%.
Table 1 shows the composition of the metal film of Comparative Example 3 and the layers formed.

(Comparative Example 4)
As the powder material for forming the metal film, the above-mentioned base powder to which essential additives and optional additives are added is used, and the pretreatment film after cutting is quenched by laser without applying carbon. A metal film was formed in the same manner as in Example 1, except that the treatment was performed. Carbon (C: UF4 manufactured by Höganäs) with a particle size of 25 μm was used as an essential additive. Copper (Cu: Distaloy ACu manufactured by Höganäs) with a particle size of 25 μm was used as the selective additive. In the material powder, carbon is adjusted so that the volume content of the final material powder is 12%. Also, copper is adjusted so that the volume content of the final material powder is 2%.
Table 1 shows the composition of the metal film of Comparative Example 4 and the layers formed.

(Comparative Example 5)
A metal film was formed in the same manner as in Example 1 except that the laser output during the quenching treatment was 950 W and the temperature was 1200°C.
Table 1 shows the composition of the metal film of Comparative Example 5 and the layers formed.

(Comparative Example 6)
A metal film was formed in the same manner as in Example 1, except that the application speed during the quenching treatment was 40 mm/min.
Table 1 shows the composition of the metal film of Comparative Example 6 and the layers formed.

Next, cross-sectional images of joined bodies produced in each example will be described with reference to FIGS. 11 to 20. FIG. 11 is a diagram showing a cross-sectional image of Example 1. FIG. FIG. 12 is a diagram showing a cross-sectional image of Example 2. FIG. FIG. 13 is a diagram showing a cross-sectional image of Example 3. FIG. FIG. 14 is a diagram showing a cross-sectional image of Example 4. FIG.
15 is a diagram showing a cross-sectional image of Comparative Example 1. FIG. 16 is a diagram showing a cross-sectional image of Comparative Example 2. FIG. 17 is a diagram showing a cross-sectional image of Comparative Example 3. FIG. 18 is a diagram showing a cross-sectional image of Comparative Example 4. FIG. 19 is a diagram showing a cross-sectional image of Comparative Example 5. FIG. 20 is a diagram showing a cross-sectional image of Comparative Example 6. FIG.

Furthermore, for Example 1, Example 3 and Comparative Example 2, an EBSD (Electron Back Scatter Diffraction) analysis of the surface layer of the metal film was performed. The EBSD analysis results are shown in Figures 21-23. 21 is a diagram showing the EBSD analysis results of the conjugate according to Example 1. FIG. 22 is a diagram showing the EBSD analysis results of the conjugate according to Example 3. FIG. 23 is a diagram showing the EBSD analysis results of the conjugate according to Comparative Example 2. FIG. In FIGS. 21 to 23, α-iron (Iron-Alpha), γ-iron (Iron-Gamma), iron-carbide (Iron-Carbide), and graphite (Graphite) are indicated by changing the density of hatching.

11 to 14, 21 and 22, it can be seen that a first hard layer 211, a second hard layer 212, and a heat affected zone 213 are formed in the joined bodies according to Examples 1 to 4. FIG. 11 and 12, it can also be confirmed that a non-heat-affected zone 214 is formed.

On the other hand, from FIGS. 15 to 20 and 23, Modifications 1 to 6 are bonded bodies in which the first hard layer 211, the second hard layer 212, and the heat affected zone 213 are not formed, and the heat affected zone 213 It can be seen that the joined body is formed only with only one layer.

Next, hardness measurement (micro Vickers hardness test: Hv 0.025) was performed for Examples 1 to 4 and Comparative Examples 1 to 4. The hardness measurement results are shown in FIGS. 24 to 31 and Table 2. 24 is a diagram showing hardness measurement results of Example 1. FIG. 25 is a diagram showing hardness measurement results of Example 2. FIG. 26 is a diagram showing hardness measurement results of Example 3. FIG. 27 is a diagram showing hardness measurement results of Example 4. FIG. 28 is a diagram showing hardness measurement results of Comparative Example 1. FIG. 29 is a diagram showing hardness measurement results of Comparative Example 2. FIG. 30 is a diagram showing hardness measurement results of Comparative Example 3. FIG. 31 is a diagram showing hardness measurement results of Comparative Example 4. FIG. 24 to 31 show cross-sectional images of each example in association with the depth from the surface of the metal film.

From Table 2 and FIGS. 24 to 31, the first hard layer forming the surface of Examples 1 to 4 has a hardness of Hv600 or more, whereas in Comparative Examples 1 to 4, the heat affected zone and the non-heat affected zone are It can be seen that the surface is formed and the hardness is less than Hv600. From these results, it can be seen that Examples 1-4 have higher hardness than Comparative Examples 1-4.

INDUSTRIAL APPLICABILITY As described above, the bonded body and the manufacturing method of the bonded body according to the present invention are suitable for obtaining a lightweight bonded body having high strength and hardness.

Reference Signs List 1 joined body 10 substrate 20 metal coating 21 first hard layer 22 second hard layer 23 heat affected zone 24 non-heat affected zone 30 cold spray device 31 gas heater 32 powder supply device 33 spray gun 34 gas nozzle 35, 36 valve 200 Pretreatment film

Claims (3)

a base material containing aluminum or an aluminum alloy as a main component;
a metal film containing iron as a main component and carbon as an essential additive, the metal film being laminated on and bonded to the base material;
with
The metal film is
a first hard layer forming a surface opposite to the base material side and made of cementite and martensite;
a heat affected zone having a hardness lower than that of the first hard layer and made of ferrite, martensite and retained austenite;
a second hard layer provided between the first hard layer and the heat affected zone and made of martensite and retained austenite;
A conjugate characterized by having The first hard layer has a Vickers hardness of Hv600 or more,
The joined body according to claim 1, wherein the heat affected zone has a Vickers hardness of Hv200 or more and Hv400 or less. 2. The joint of claim 1, wherein said metal coating further comprises a selective additive comprising at least one of copper, molybdenum, chromium, nickel and manganese.

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