JPH05294739A - Titanium diboride-based sintered compact and its production - Google Patents

Abstract

PURPOSE:To provide a titanium diboride-based sintered compact having high strength, high hardness, excellent corrosion and heat resistance and very high fracture toughness. CONSTITUTION:A titanium diobride-based compact contg. 0.5-99.5 pts.wt. (expressed in terms of V and Mo) vanadium compd. and/or molybdenum compd., 1-50 pts.wt. nitride, 0.5-10 pts.wt. carbon and 1-50 pts.wt. zirconium oxide in titanium diboride is subjected to atmospheric sintering at 1,600-2,200 deg.C in vacuum or in a nonoxidizing atmosphere to produce the objective titanium diboride-based sintered compact.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a titanium diboride-based sintered body useful as a material having high hardness, abrasion resistance and heat resistance, and a method for producing the same.

[0002]

Conventionally, titanium diboride-based sintered bodies have been required to have high hardness and wear resistance, heat resistance, etc. for cutting tools, heat resistant materials, heat engine parts materials, rocket materials, etc. It is known that it is extremely useful as a material to be used or a material utilizing high electric conductivity.

However, since titanium diboride alone has poor sinterability, the obtained sintered body itself has a low bending resistance and is fragile. Therefore, it has been proposed to add various binders to increase the strength thereof. For example, Ti, Cr, V, Ta, Nb, Mn, Mo.
A method in which at least one kind of metal boride and the like, and a binder metal compound are used as basic components, and an additive selected from metal carbides, silicides, nitrides or oxides is added to this and sintered. 57-42578), addition of zirconium oxide powder (JP-A-58-55378), addition of complex boride of Fe, Co, Ni and W (JP-A-60-103080), addition of molybdenum silicide. (JP-A-60-195061), addition of metal boride and titanium carbonitride (JP-A-61-97169), various metal sintering aids or auxiliary components as a composite agent, and sintering. It is known how to do it.

However, many of the above methods are by hot pressing, and those manufactured by pressureless sintering have problems such as insufficient bending strength and low fracture toughness.

[0005]

In view of the present situation, the present inventors have considered that the titanium diboride sintered body has high strength and high hardness,
As a result of extensive studies on imparting heat resistance and toughness, it was found that the addition of zirconium oxide powder as an additive together with vanadium compound and / or molybdenum compound, carbon and nitride greatly improves the fracture toughness. The invention has been reached.

That is, the present invention relates to titanium diboride (Ti
B ₂ ) 100 parts by weight of vanadium compound and /
Alternatively, the molybdenum compound is 0.5 to 99.5 parts by weight in terms of vanadium (V) or molybdenum (Mo), the nitride is 1 to 50 parts by weight, the carbon is 0.5 to 10 parts by weight, and zirconium oxide (ZrO ₂ ). A titanium diboride-based sintered body containing 1 to 50 parts by weight, and titanium diboride (Ti
B ₂ ) 100 parts by weight of vanadium compound and /
Alternatively, the molybdenum compound is 0.5 to 99.5 parts by weight in terms of vanadium (V) or molybdenum (Mo), the nitride is 1 to 50 parts by weight, the carbon is 0.5 to 10 parts by weight, and zirconium oxide (ZrO ₂ ). 1 to 50 parts by weight of and mixed with a molded body, which is subjected to atmospheric pressure sintering in a temperature range of 1600 to 2200 ° C. in a vacuum or a non-oxidizing atmosphere, and a titanium diboride-based sintered body is characterized. Is a manufacturing method.

The titanium diboride used in the present invention may be produced by any method such as a direct reaction with metallic titanium or a method utilizing a reduction reaction of oxides such as titania. It is preferable that the powder has high purity and is a fine powder. Specifically, the purity is 98% or more, the average particle size is 5 μm or less, and more preferably 2 μm or less.

The vanadium compound added in the present invention includes V, VC, VB, VB ₂ , VO, V ₂ O ₅ , VN and V ₃ N, and preferably VC, VB, VN are used.

Molybdenum compounds include Mo and M
oSiO ₂ , MoN, MoO ₂ , MoO ₃ , MoC, M
oB, Mo ₂ B, MoB ₂ and MoSi _2, etc.,
Preferably MoN, MoC, MoB, MoB ₂ , MoSi
₂ is used.

The particle size of the vanadium compound or molybdenum compound is preferably 10 μm or less, more preferably 5 μm or less. When adding the above compounds, one kind of each of the above compounds may be added, or some of them may be selected and added together.

The total amount of addition of titanium diboride (hereinafter abbreviated as main component) is 0.5 in terms of V or Mo.
˜99.5 parts by weight, and if less than 0.5 parts by weight, grain growth of the sintered body occurs, so the obtained sintered body does not have high strength and high toughness, while it is more than 99.5 parts by weight. In this case, the amount of the additive increases in the sintered body, resulting in a decrease in bending strength, which is not preferable.

Next, regarding nitrides, the nitrides added in the present invention are TiN, ZrN, TaN, NbN,
CrN, AlN, BN, etc., whose particle size is 1
It is preferably 0 μm or less, and particularly preferably 5 μm or less.

The amount of addition of these nitrides is 1 to the main component.
If it is less than 1 part by weight, the toughness is not improved. On the other hand, if it is more than 50 parts by weight, the bending strength is lowered, which is not preferable.

Next, regarding the addition of carbon, the main purpose of the addition of the carbon material is to promote the sintering, and the oxide contained in the titanium diboride powder (eg Fe, C).
(a, Mg, Nb, etc.) and oxygen in the atmosphere are removed, and an extremely useful action is provided for maintaining a non-oxidizing atmosphere.

Examples of the carbon source include petroleum coke, graphite, carbon black and thermosetting resins such as carbonizable phenol resin, furan resin, polyimide resin, polyurethane resin, melamine resin and urea resin,
Examples include tar products such as petroleum tar and pitch. Among these, carbon black, graphite,
Phenolic resins and furan resins are preferred.

The amount of carbon source added is 0.5 to the main component.
10 parts by weight, if less than 0.5 parts by weight, it is difficult to densify. On the other hand, if more than 10 parts by weight, free carbon is contained in the sintered body and grain growth occurs, causing deterioration of physical properties. Therefore, addition within this range is preferable.

In the present invention, zirconium oxide is further added to the above additives. Its main purpose is to improve the toughness of the sintered body. The particle size of zirconium oxide added is 1
It is preferably 0 μm or less, and particularly preferably 5 μm or less.

The amount of zirconium oxide added is 1 to 50 parts by weight with respect to the main component. If it is less than 1 part by weight, the toughness improving effect does not appear, while if it is more than 50 parts by weight, the hardness of the sintered body decreases. Therefore, addition within this range is preferable.

As described above, according to the present invention, a predetermined amount of the above-mentioned additive is added to the main component titanium diboride. Next, the mixing of the above-mentioned composition powder can be carried out by a commonly used method. As an example, a method using a ball mill or the like and mixing in an organic solvent can be adopted. As the organic solvent used in this case, hydrocarbons such as petroleum, ether, hexane, benzene and toluene, and aliphatic alcohols such as methanol, ethanol, propanol and isopropanol are used.

The mixing may be carried out for about 5 to 24 hours, whereby the aggregated and condensed powders are crushed and uniformly mixed. After removing the solvent, for example, mold molding,
It is formed by rubber press molding or the like, and is sintered under normal pressure in a vacuum or an inert gas atmosphere such as argon, helium, or nitrogen.

The sintering temperature is 1600 to 2200 ° C., and the sintering time is 0.5 to 10 hours, though it depends on the shape and the like. When the temperature is lower than 1600 ° C., the sintering is insufficient and the relative density is low, while when it is higher than 2200 ° C., grain growth occurs, which causes deterioration of the bending strength and the like, and is also disadvantageous in terms of thermal energy.

It is also possible to fill the raw material powder in a graphite mold of a conventional method, and hot-press and sinter it. The sintered body obtained according to the present invention has a dense crystal structure by using the above-mentioned sintering aid or additive, specifically, most of the crystal is 5 μm or less and is extremely dense and fine. It has a crystalline structure.

In the present invention, the fracture toughness value is greatly increased largely due to the addition of vanadium compound and / or molybdenum compound and nitrides such as carbon, TiN, TaN, etc., and zirconium oxide. This is the reason why a sintered body having no high strength and high toughness can be obtained.

The sintered body obtained in the present invention is excellent in strength, hardness and toughness due to the mutual effect of the additive aids. Specifically, the bending strength is 85 kg / mm ² or more and the room temperature hardness HV. Is 2000 kg / mm ² or more and the fracture toughness value is 5 MN / m ^3/2 or more.

[0025]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to the examples.

Examples 1 to 8 Vanadium compound, molybdenum compound, nitride, carbon and zirconium oxide were added to 100 parts by weight of TiB ₂ powder (average particle size: 1 μm, purity: 99%). Sample composition), and using a hexane solvent, wet ball mill mixing was performed with a nylon pot and nylon balls for 24 hours.

The mixture is then dried and the mold diameter 15
mm, 10 mm thick disc, and 1.5t
Rubber pressing was performed at a pressure of on / cm ² to obtain a molded product having a predetermined size. This molded body was placed in a graphite crucible and heated at a temperature of, for example, 1950 ° C. (Example 1) in an argon gas atmosphere,
Pressureless time sintering was performed. Table 1 shows the sintering conditions and various physical properties of the obtained sintered body. The sintered body shrinks uniformly,
No deformation was observed at all, and as a result of observation with an electron microscope (SEM), the structure had an extremely dense crystal structure in which particles having an average particle size of 5 μm or less were uniformly dispersed. The characteristics of the obtained sintered body are shown in Table 1.

[0028]

[Table 1]

Comparative Examples 1 to 6 A sample having the sample composition shown in Table 2 was prepared in the same manner as in Example 1 to obtain a molded body, which was treated under predetermined firing conditions, and the obtained results were simultaneously displayed as a comparative example. 2 shows.

[0030]

[Table 2]

As is apparent from the table, when comparing the physical properties of the titanium diboride-based sintered bodies, their fracture toughness values,
It can be seen that the bending strength and hardness of the examples of Table 1 are significantly superior to the corresponding comparative examples, and the mechanical properties of the sintered body are improved.

[0032]

The sintered body of the present invention is not only high in strength and hardness, excellent in corrosion resistance and heat resistance, but also extremely high in fracture toughness, and according to the method of the present invention. For example, since it is possible to obtain a sintered body with such excellent physical properties by pressureless sintering, it is possible to manufacture complex shapes, such as machining materials such as cutting materials, wear-resistant materials such as drawing dies, and other two materials. It can be used in various applications where the characteristics of titanium boride-based sintered bodies are exhibited, and is of great practical value.

Claims (2)

[Claims] 1. A vanadium compound and / or a molybdenum compound in an amount of 0.5 to 99.5 parts by weight in terms of vanadium (V) or molybdenum (Mo) per 100 parts by weight of titanium diboride (TiB ₂ ) and a nitride. 1-50 parts by weight, carbon 0.5 to 10 parts by weight of zirconium oxide (ZrO ₂₎ and containing 1 to 50 parts by weight titanium diboride based sintered body. 2. A vanadium compound and / or a molybdenum compound in an amount of 0.5 to 99.5 parts by weight in terms of vanadium (V) or molybdenum (Mo) based on 100 parts by weight of titanium diboride (TiB ₂ ) and a nitride. 1 to 50 parts by weight of carbon, 0.5 to 10 parts by weight of carbon, and 1 to 50 parts by weight of zirconium oxide (ZrO ₂ ) were added and mixed, and the molded body was heated in vacuum or in a non-oxidizing atmosphere at a temperature of 160.
A method for producing a titanium diboride-based sintered body, which comprises performing atmospheric pressure sintering within a range of 0 to 2200 ° C.