JPH045722B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a ceramic molded body having an integrally bonded hard surface layer and a method for producing the same. More specifically, the present invention provides a structure in which a hard ceramic layer is integrally formed on the surface of a molded body made of a boride-metal composite material with high strength and high toughness, which is suitable for cutting tools and wear-resistant materials. The present invention relates to a new structure and a method for producing the same using simple equipment and simple means.

BACKGROUND ART Conventionally, as a method for manufacturing a molded body having a hard layer on the surface, for example, a metal substrate is coated with
Known methods include coating a hard ceramic layer by CVD, PVD, thermal spraying, etc., and hardening the metal surface by carburizing, nitriding, and the like.

However, the conventional method of forming a hard layer using a coating method has the disadvantage that the hard layer tends to peel off due to a difference in thermal stress between the hard layer and the base metal. In order to prevent this peeling, it is necessary to apply a coating consisting of a plurality of layers of different types, but this inevitably complicates the manufacturing process and increases costs.

On the other hand, although the method of hardening the metal surface by carburizing or nitriding can lower the cost compared to the above-mentioned coating method, it has the drawback of not being able to obtain a metal that is sufficiently hard.

Problems to be Solved by the Invention The purpose of the present invention is to improve the drawbacks of such conventional molded products having a hard layer on the surface, and to create a material with high strength and high toughness suitable for cutting tools and wear-resistant materials. It is an object of the present invention to provide a novel ceramic molded article which has a hard surface layer which is integrally bonded to a substrate and does not peel off.

Means for Solving the Problems The present inventor has conducted extensive research to develop a ceramic molded product that has both high strength and high toughness and has a hard layer on the surface that does not peel off. The inventors have discovered that the objective can be achieved by integrally forming a hard ceramic layer on the surface of a substrate in which metal borides are bonded by metal, and based on this knowledge, the present invention has been made. .

That is, the present invention applies to Group A and Group A of the periodic table.
On the surface of a substrate consisting of a boride of at least one metal selected from Group VA, a metal from which the metal boride was formed, and a bonding metal selected from metals from Group B of the periodic table, A ceramic molded article characterized in that a hard ceramic layer consisting of a boride of a group metal or a group VA metal or a dispersion of another hard ceramic in the boride is integrally laminated, and the production thereof. (A) When forming a metal boride with a powder of at least one metal selected from Groups A and VA of the periodic table and boron powder, the former is present in a stoichiometric excess in the mold. A mixture of proportions or periodic table A
Filled with a base-forming component consisting of a stoichiometric mixture of powder of at least one metal selected from Groups Groups and Groups VA and boron powder, to which a metal of Group B of the periodic table is added; (B) Then over it,
A component for forming a hard ceramic layer comprising a mixture of a powder of at least one metal selected from Groups A and Group VA of the periodic table and boron powder in a stoichiometric ratio, or a mixture thereof with hard ceramic powder. The present invention provides a method for producing a ceramic molded body, which is characterized in that after being coated with a layer, the powder mixture in contact with the inner bottom of the mold under vacuum is ignited, and an exothermic reaction is allowed to proceed while pressurizing from above.

The molded article of the present invention is suitable for group A and VA of the periodic table.
The substrate is a boride-metal composite material in which at least one boride selected from the group of metals belonging to the group of titanium, zirconium, hafnium, niobium, and tantalum is bonded with a bonding metal. It has a tissue structure with a ceramic layer. As the bonding metal, metals from Group A and Group A of the periodic table used as the components of the above-mentioned boride are used.
Metals from Group VA or metals from Group B of the periodic table that do not form borides when reacted with boron, namely copper, gold, and silver, are used.

The composition of this substrate is preferably in the range of 50 to 99% by weight of the metal boride and 50 to 1% by weight of the bonding metal.

The hard ceramic layer provided on the surface of the substrate may be made of hard ceramic such as metal nitride, carbide, boride, or oxide itself, or powder of hard material such as these metal compounds, boron carbide, silicon carbide, or nitride. Cetamics in which powders of boron, diamond, etc. are dispersed may also be used.
Particularly preferred are layers composed of the metal borides themselves, which are constituents of the substrate.

It is sufficient that this hard ceramic layer is formed on the surface of the substrate to a thickness of at least 1 mm.

In the molded article of the present invention, it is necessary that the base made of the above boron compound-metal composite material and the hard ceramic layer are integrally bonded.

According to the method of the present invention, such a molded article is (A)
A powder of a metal belonging to Group A or Group VA of the periodic table, which is necessary to generate the boride present in the substrate, and boron powder are mixed in a proportion such that the former is in stoichiometric excess. This mixture is filled into a mold, and the surface is then covered with (B) powder of a metal belonging to Group A or Group VA of the periodic table and boron powder.
After being coated with a stoichiometric amount of the mixture or a proportion of the latter in excess, the mold is ignited near the bottom, allowing the exothermic reaction to propagate gradually towards the top, resulting in the formation of boride and the formation of metal. It can be manufactured by melting.

At this time, it is necessary to carry out the reaction under vacuum while applying pressure from above in order to ensure the production of the boride and to make it compact.

Through this reaction, a boride of a metal of Group A or Group VA of the periodic table is generated in the base portion, and the excess metal is melted and the boride is bonded to form a boron compound-metal composite material. . On the other hand, a hard ceramic layer consisting only of borides of the same metal is formed on the surface.
This is integrally bonded to the base portion.

In (A) above, Group A or VA of the periodic table
Instead of using an excess of group metal as a binder, the excess can also be replaced by a metal that does not react with boron, such as a metal from group B of the periodic table or an alloy thereof. Further, as a raw material for forming the hard ceramic layer, hard ceramic powder such as B ₄ C, Al 2 is added to a mixture of metal powder of Group A or Group VA of the periodic table and boron powder in a stoichiometric _ratio.
It is also possible to use powders such as O ₃ , ZrO ₂ , TiC, SiC, cubic boron nitride, and diamond. The appropriate blending ratio of this hard ceramic powder is in the range of 10 to 95% by weight.

The method of the present invention needs to be carried out under pressure, and this pressurization can be carried out by any means such as spring compression, hydraulic press, or hydrostatic compression.
It is carried out at a pressure of cm ² . This pressurization is preferably carried out in such a manner that the pressure is applied parallel to the direction of progress of the exothermic reaction.

Next, ignition to start the reaction can be performed by, for example, inserting an ignition jig made of two tungsten wires with platinum wire welded to the ends near the bottom of the mold and passing an electric current through the ignition jig. .

In order to ensure the densification of the hard ceramic layer in the molded product of the present invention, a heat absorbing plate such as a metal copper plate is placed on the surface of the raw material mixture B for forming the hard ceramic layer, and the heat absorbing plate such as a metal copper plate is placed on the surface of the raw material mixture B for forming the hard ceramic layer. , it is desirable to promote endothermic cooling.

The molded article of the present invention can be molded into any shape, such as a plate, rod, cylinder, cylinder, or block, by appropriately selecting the shape of the mold.

Effects of the Invention According to the present invention, on the surface of a substrate made of a boronide-metal composite material having high strength and high toughness,
A ceramic molded body having a hard ceramic layer can be produced using simple equipment and operations.

The ceramic molded body of the present invention is suitably used as, for example, a cutting tool or a wear-resistant material.

Examples Next, the present invention will be explained in more detail with reference to Examples.

Example 1 A metal mold heat-insulated with graphite was placed in a container that could be depressurized, and the mold was filled with a mixed powder of titanium and boron powder mixed thoroughly at a molar ratio of 11:9. , a mixture of titanium and boron powders sufficiently mixed in a molar ratio of 1:2.
Filled with a thickness of mm.

Next, a metal copper plate was placed in contact with the surface of the mixed powder layer of titanium and boron in a molar ratio of 1:2, and a pressure of 200 kg/cm ² was applied from above and below to compress the spring and simultaneously compact the powder. A current was instantaneously passed through an ignition jig (a platinum wire with a diameter of 0.2 mm was welded to the ends of two tungsten wires) to ignite the end of a mixed powder layer of titanium and boron in a molar ratio of 11:9. , started the reaction.

As the reaction progresses from the edges of the green compact, approximately
In the combustion zone heated to 3000K, a synthesis reaction of titanium boride and the melting of an excess amount of titanium occur, and densification progresses.The contraction caused by the reaction is successively compensated for by the expansion of the spring, resulting in densification. The required pressure is continuously applied to the sample.

After the reaction was completed, the molded body was cooled and taken out from the mold, and a molded body having a titanium diboride layer with excellent peelability on both sides of TiB-Ti was obtained.
The surface hardness of this product was 3100 Kg/mm ² .

Further, when the cross section was observed using an electron microscope, it was found that the bond between the base portion and the hard ceramic portion was continuous and integrated.

Example 2 A hard layer was formed using a mixed powder containing titanium powder and boron powder at a molar ratio of 1:2 and copper powder at 3% by weight as a raw material composition for forming the base. A mixed powder containing 50% by weight of _B4 powder was used as a raw material composition containing titanium powder and boron powder at a molar ratio of 1:2, and the same method as in Example 1 was used. By causing the reaction to occur, a molded body having a structure in which a B ₄ C dispersed layer was integrally laminated on the surface of a substrate made of a TiB ₂ -Cu composite material was obtained.

The surface hardness of this product was 3130 Kg/mm ² .

Example 3 A mixed powder containing zirconium powder and boron powder at a molar ratio of 1:1 was used as the raw material composition for forming the base, and zirconium powder was used as the raw material composition for forming the hard layer. By reacting in the same manner as in Example 1 using a mixed powder containing boron powder and boron powder at a molar ratio of 1: ₂ , ZrB ₂ hard A molded body having a structure in which layers were integrally laminated was obtained.

The surface hardness of this product was 2050 Kg/mm ² .

Example 4 A mixed powder containing titanium powder and boron powder at a molar ratio of 11:9 was used as the raw material composition for forming the base, and titanium powder was used as the raw material composition for forming the hard layer. By reacting in the same manner as in Example 1 using a mixed powder containing 20 wt. A molded body having a structure in which a CBN-dispersed ceramic layer was integrally laminated on the surface of a substrate made of a -Ti composite material was obtained.

The surface hardness of this product was 3900Kg/ ^mm2 .

Example 5 A mixed powder containing niobium powder and boron powder at a molar ratio of 1:2 and 3% by weight of copper powder was used as the raw material composition for forming the substrate, and a hard layer was formed. When a mixed powder of niobium powder and boron powder with a molar ratio of 1:2 was used as a raw material composition for the reaction, the reaction was carried out in the same manner as in Example ₁ . A molded body having a structure in which _two NbB layers were integrally laminated was obtained.

The surface hardness of this product was 2340 Kg/mm ² .

Example 6 A mixed powder containing tantalum powder and boron powder at a molar ratio of 3:4 and 3% by weight of copper powder was used as the raw material composition for forming the substrate, and a hard layer was formed. By using a mixed powder of tantalum powder and boron powder at a molar ratio of 3:4 as a raw material composition for the reaction in the same manner as in Example 1, a substrate made of a Ta ₃ B ₄ -Cu composite material was prepared. A molded body having a structure in which _four Ta ₃ B layers were integrally laminated on the surface was obtained.

The surface hardness of this product was 2970 Kg/mm ² .

Claims (1)

[Scope of Claims] 1. A boride of at least one metal selected from Groups A and VA of the Periodic Table, and a metal selected from the metal forming this metal boride and a metal of Group B of the Periodic Table. A hard ceramic layer made of a boride of a metal of Group A or Group VA of the periodic table or a material in which another hard ceramic is dispersed in the boride is integrally laminated on the surface of a base made of a bonding metal. A ceramic molded body characterized by: 2 (A) When a metal boride is formed between powder of at least one metal selected from Groups A and VA of the periodic table and boron powder in the mold, the ratio at which the former becomes stoichiometrically excessive; A mixture of or periodic table A
Filled with a base-forming component consisting of a stoichiometric mixture of powder of at least one metal selected from Groups Groups and Groups VA and boron powder, to which a metal of Group B of the periodic table is added; (B) Then over it,
A component for forming a hard ceramic layer comprising a mixture of a powder of at least one metal selected from Groups A and Group VA of the periodic table and boron powder in a stoichiometric ratio, or a mixture thereof with hard ceramic powder. Ceramics in which a hard ceramic layer is integrally laminated on the surface of a substrate, which is characterized by igniting the powder mixture in contact with the inner bottom of the mold under vacuum after being coated with a layer, and allowing an exothermic reaction to proceed while pressurizing from above. Method for manufacturing a molded object.