JPS6033336A - Crystal boron nitride sintered body and preparation thereof - Google Patents

Abstract

PURPOSE:To inexpensively prepare a CBN sintered body having an arbitrary dimension and configuration, by dispersing CBN fine particles having a specific volumetric ratio range in a bonding material obtained by alloying a hard heat resistant inorg. compound and a metal according to a liquid phase sintering process. CONSTITUTION:A fine powder comprising a hard heat resistant inorg. compound (e.g., TiN, WC or AlN), a powder comprising a metal alone (e.g., Ni, Co or Ti) and a CBN powder in a volumetric ratio of 60-40% are mixed. In the next step, this powdery mixture is charged in a mold and pressed to 0.3-3kb under vacuum or in an inert atmosohere and heated to 1,200- 1,600 deg.C to obtain a sintered body. The press heating equipment in this case is a so called hot press apparatus and the sintered body with an extremely large dimension can be obtained by small scale equipment as compared with an ultra-high pressure apparatus and operation is also simple. The above mentioned materials of the bonding material are used in forming a CBN sintered body satisfying requirements without necessitating ultra-high pressure but it is necessary to properly select a combination of various materials and a compounding ratio and a sintering treatment condition such as pressure or a temp. This fact shows possibility such that various CBN sintered bodies having different characteristics can be manufactured according to use purpose.

Description

DETAILED DESCRIPTION OF THE INVENTION Cubic boron nitride, also referred to as OBN, is supplied as a powder produced by ultra-high pressure and high temperature technology. As an abrasive grain, it is second only to diamond in hardness, has better thermal stability than diamond, and because it does not easily react with iron, it is prized for applications such as grinding of steel, which diamond cannot match.

Also, OBN sintered bodies are known and are used as cutting tool materials and wear-resistant side slopes. Generally the thickness is 0. Ri~1
3 tm OBN sintered body with cemented carbide backing and supplied as platelet material in total thickness quantities. Conventionally, the sintered body is a mixed powder of OBN powder and a binder at a temperature of 0 to 60K.
Ultra-high pressure of A (kilobar) and /, 2θO~! 100℃
It is manufactured using a method of processing at high temperatures, that is, within the stability region of CBN. Because it requires ultra-high pressure and high temperature treatment, it is difficult to produce and expensive to produce, and there are also significant restrictions on the size and shape of the fired crystals.

The purpose of the present invention is to manufacture CBN sintered bodies of arbitrary dimensions and shapes at low cost.
3-J xb, that is, a method for producing a CBN sintered body that can be used in practical use within the pressure range of a normal powder compacting machine has been completed.

The key to making this possible is the binding material. The binder has a volume ratio of l/, 0 to 60%, and the material is a mixture of a hard, heat-resistant inorganic compound and a single metal, which react with each other under the temperature and pressure of the sintering process and are relatively stable. generating a low melting point liquid phase;
Also, the liquid phase has a property of wetting CBN well.

The presence of CBN in the liquid phase means a kind of chemical reaction on the surface of the CBN grains, which causes strong adhesion between the CBN grains and the binder, especially the liquid phase component. Furthermore, since the liquid phase is generated by a reaction, it easily overflows the remaining in-phase components of the bond, so that the bond material itself is strengthened by alloying by liquid phase sintering.

That is, the OBN particles are strongly bonded to each other with a strong binder interposed therebetween. Furthermore, since the liquid phase penetrates into the gaps between the fine particles and fills them, each particle of OBN and binder is bonded on its entire surface to form a strong sintered body, and the air cells remain to increase the strength. There is no risk of damage.

The hard heat-resistant inorganic compound is titanium nitride (TiN).

Titanium carbide TiO, titanium nitride carbide TBh+, c
); titanium boride TiB2, titanium oxide Tio,
, carbide ta:/gesten Wc, aluminum nitride A7N
, aluminum oxide A/, O, etc., and simple metals (IJ4, CO, titanium Ti, silicon Sα, etc.) are useful.

A fine powder of one or more of these inorganic compounds and one or more of the single gold particles is mixed with OBN powder and loaded into a molding shop, and then placed in a vacuum or inert atmosphere. Sintering is completed by applying pressure to 03-3 KA and heating to 100-8θO°C.

The pressurizing and heating equipment is a so-called pot press equipment, which can produce sintered bodies of much larger size with small-scale equipment than ultra-high pressure equipment, and is easy to operate. or as a material for wear-resistant parts,
Hardness to resist wear, toughness to prevent fracture, and heat resistance to maintain these mechanical properties up to high temperatures are required. The above-mentioned mutual bonding of binders satisfies this requirement without requiring ultra-high pressure (3
In order to produce a BN sintered body, it is necessary to appropriately select the combination of various side slopes, the compounding ratio, and the sintering conditions such as pressure and temperature. This also suggests the possibility of producing various OBN sintered bodies with different properties depending on the purpose of use.

In order to manufacture an OBN sintered body having a cemented carbide backing, in the above-mentioned manufacturing method, a predetermined amount of silver in a mixed powder containing CBN is loaded into the mold, and then WC and C of super-hi alloy materials are loaded.
If the mixed powder with O is loaded and hot pressed, 1
A two-layer sintered body is obtained by sintering it into a body.

Example 1 Fine powder having the composition shown in Table 7 was mixed, filled into a graphite mold, placed in a vacuum hot press device, and gradually heated while maintaining a pressure of /KA until a sintering temperature of 13σθ°C was reached at 60°C. Hold for minutes,
After cooling to room temperature while keeping the pressure applied, the pressure was removed and the sample was taken out. The obtained sintered body has a volume ratio of CB in the base of the binder.
It exhibits a dense composite sintered alloy structure in which N particles are dispersed, the transverse rupture strength is approximately tolr, g/cl, and the hardness by scratch test far exceeds that of the 1.20 class cemented carbide. This OBN
Sintered bodies are excellent as wear-resistant materials.

Table 7 Table a Table 3 The fine powder mixture of Example C and Table C was prepared in the same manner as in Example 1.
/Kb Sintering treatment was performed at 1300°C for 60 minutes. The obtained sintered body has transverse rupture strength! ;Okg/ad, scratch hardness is 2
It is much larger than Type 0 cemented carbide. This OBN sintered body is excellent as a cutting tool material.

Example 3 A fine mixed powder having the composition shown in Table 3 was prepared in the same manner as in Example 1.
/Kb/7θθ°C for 60 minutes. Although the obtained sintered body is slightly inferior to those of Example 1 in terms of transverse rupture strength and hardness, it is also superior to cemented carbide as a wear-resistant material.

Claims (3)

[Claims] (1) A hard heat-resistant inorganic compound and gold scrap are mixed into a binder alloyed by liquid phase sintering, and OBN is added to the binder with a volume ratio of 60 to 10%.
Cubic boron nitride-based sintered body with dispersed fine particles. (2) The materials of the binder are TiN, TiO, T((N, (
Ri, Ti horse. The cubic crystal laminated boron sintered body according to claim 1, which is a mixed powder of one or more of Tioz, wC, htx, and h401+. (3) Hard heat-resistant inorganic compound powder and O
Gold scrap powder that generates a liquid phase containing BN and a volume ratio of AO~
A method for producing a CBN sintered body, characterized by sintering a mixed powder with Q% of qBN powder at a pressure of 03 to 3 Kb (kilobar) and at a temperature of θθ to 00°C in a warm summer.