RU2223929C1 - Method for making ceramic material - Google Patents

Abstract

FIELD: chemical technology, ceramics. SUBSTANCE: invention relates to manufacture of ceramic material, namely, to making cutting tool used fro treatment of cast iron, steel, alloys based on thereof and other materials. Method for making ceramic material involves mixing powder-like composite of aluminum, titanium, magnesium oxide, titanium carbide and cubic boron nitride in ball mill and hot pressing under pressure. After mixing charge is briquetted under pressure 0.06-0.15 GPa at room temperature followed by annealing at temperature 1200-1400 C for 1-5 min. Hot pressing is carried out in argon or nitrogen medium or in vacuum under pressure 0.02-0.08 GPa with exposition for 5-20 min. Cubic boron nitride with particles size 1-5 mcm and oxides and carbide of charge with particles size 0.101.0 mcm are used. Method provides preparing articles with high resistance to wear, large scale without using special energetic equipment for creation of superhigh pressure values. EFFECT: improved making method. 1 tbl, 1 ex

Description

The invention relates to the production of ceramic material, in particular to the manufacture of a cutting tool used to process cast iron, steel, alloys based on it and other materials.

Known ceramic material based on cubic boron nitride, sintered under high pressure, containing 20-48% of the decomposing reaction phase formed from one or more compounds containing oxygen: Ti ₂ AlN, Ti ₂ AlC, AlN (Japan JP 3035797 B2, 5017233 A Cl. C 04 B 35/58, publ. 24.04.2000). For the manufacture of such a material, the use of ultrahigh pressures is necessary, which is its drawback.

A known method of manufacturing ceramic products, which consists in mixing the initial powders of cubic boron nitride 10-80%, diamond powder 5-60%, carbides, nitrides, carbonitrides of metals IVa and Va subgroups or carbides VIa subgroups in total 5-60%, cubic additives carbonitride and inevitable impurities. The material is sintered at ultrahigh pressures (> 5 GPa) (application 62-19394, Japan MKI ⁴ C 04 V 35/58, 1987).

The disadvantage of this method is the low wear resistance, the need to use sophisticated energy equipment for the production of sintering at ultrahigh pressure and, as a result, the high cost of obtaining products.

Closest to the claimed technical solution, a method of manufacturing a material, comprising mixing a powder composition consisting of 5-40% by volume of fibrous silicon carbide and / or zirconium oxide, 10-40% by volume of one or more two compounds such as carbide, nitride or transition boride metal of groups IVa, Va and VIa of the Periodic system of elements and aluminum oxide, 2-15% by volume of one or more elements such as iron, cobalt, nickel, aluminum and silicon, the rest is cubic boron nitride (Japanese application 63-303029, MKI C 22 C 29/16, 198 8 g.). To obtain the sintered material proposed by this patent, the powder composition of the desired composition is mixed in a ball mill, the mixed composition is placed in a metal cylindrical matrix and sintering is carried out at a temperature of 1100-1673 ° C under a pressure of 3-6 GPa for a period of several minutes to tens of minutes. Sintered samples are soldered to the tops of non-turning hard alloy plates (prototype).

In this way, products can be obtained using ultra-high pressures> 3 GPa, small dimensions ≤4 mm, low wear resistance, because this method uses up to 15% by volume of one or more elements such as iron, aluminum and silicon. As you know, these metals reduce the wear resistance of ceramic materials in the processing of steels and cast irons.

The objective of the present invention is to develop a method that allows to obtain products with high wear resistance, large dimensions and without the use of special power equipment to create ultra-high pressures.

To achieve the task in a method of manufacturing a ceramic material, comprising mixing a powder composition of oxides of aluminum, titanium, magnesium, titanium carbide and cubic boron nitride in a ball mill and hot pressing under pressure, after mixing the mixture is briquetted under a pressure of 0.06-0.15 GPa at room temperature, then annealed at a temperature of 1200-1400 ° C for 1 ÷ 5 minutes, and hot pressing is carried out in an environment of either argon or nitrogen, or in vacuum under a pressure of 0.02-0.08 GPa with a holding of 5- 20 minutes at than cubic boron nitride is used with a particle size of 1-5 microns, and oxides and carbide of a charge with a particle size of 0.1-1.0 microns.

Briquetting the mixture at room temperature under a pressure of 0.06-1.5 GPa after mixing the powder composition with cubic boron nitride ensures the formation of contacts of cubic boron nitride with particles of the ceramic composition to obtain an activating layer with it during oxidative annealing.

At a pressure of less than 0.06 GPa, the briquette will be destroyed.

At a pressure of more than 1.5 GPa, a separation will occur, which will lead to delamination of the briquette and its destruction. In the process of briquette heating during annealing, starting from a temperature of 1200 ° С, in an oxidizing atmosphere up to 1400 ° С, a cubic modification of boron nitride goes into hexagonal. The process takes place on the surface of a particle of cubic boron nitride with a size of 1-5 microns. In this case, as you know, the activity of boron and nitrogen atoms increases by 10 ⁵ -10 ⁶ times and the presence of TiO ₂ , MgO, Al ₂ O ₃ and TiC near the surface of cubic boron nitride in the form of fine-grained fractions of 0.1-1.0 μm in size promotes the formation of low-melting compounds Al ₈ B ₂ O ₅ , MgTi ₂ O ₅ and Al ₂ TiO ₅ , which leads to liquid-phase activated sintering at low temperatures and makes it possible to obtain large-sized products at lower hot pressing pressures with high wear resistance.

When the annealing temperature is less than 1200 ° C, fusible compounds are not formed, and there is no effect of lowering the sintering temperature and pressing pressure, and products with a low density and, as a result, with low wear resistance will be obtained.

At temperatures above 1400 ° C, the transition of cubic boron nitride to hexagonal will occur in significant quantities, which will lead to a decrease in wear resistance.

Annealed briquettes are placed in graphite molds in which hot pressing is carried out in the temperature range 1200-1400 ° C under a pressure of 0.02-0.08 GPa in an atmosphere of inert gas, nitrogen or in a vacuum with a holding time of 5-20 minutes. Fusible joints allow intensive activated hot pressing at low temperatures, low pressures, resulting in high-density large-sized workpieces with high wear resistance.

At a temperature below 1200 ° C, and a shutter speed of less than 5 minutes, and a pressure of less than 0.02 GPa, the products are loose with low wear resistance. At temperatures above 1400 ° C, exposure for more than 20 minutes, cubic boron nitride passes into hexagonal boron nitride, resulting in a sharp decrease in wear resistance.

Example

Cubic boron nitride 15 wt.%, 15 wt.% Titanium carbide, 2 wt.% Magnesium oxide, 5 wt.% Titanium oxide and 63 wt.% Alumina were mixed in a ball mill lined with alumina by grinding bodies made of this material for 144 hours in ethyl alcohol. The resulting pulp was dried at 120 ° C. The result was a mixture of cubic boron nitride with a particle size of 1-5 microns; TiO ₂ , MgO, TiC and Al ₂ O ₃ with a particle size of 0.1-1.0 μm. Briquettes measuring 13 × 13 × 10 mm and 20 × 20 × 10 mm were pressed from the mixture thus obtained by cold pressing at a specific pressure of 0.07 GPa. Briquettes were annealed for 5 minutes in air at a temperature of 1250 ° C.

Annealed briquettes were loaded into graphite molds and subjected to hot pressing at a temperature of 1300 ° C, a pressure of 0.07 GPa with an exposure of 7 minutes in an argon atmosphere.

From the hot-pressed blanks thus obtained, cutting inserts of the SNGN 120408 form (according to ISO) with a size of 12.76 × 12.76 × 4.76 mm were obtained using a diamond tool, on which thin sections were made for determining microhardness and studying cutting properties.

Cutters were tested under the following conditions:

the processed material - S428-30 cast iron

Cutting speed 300 m / min

Feed 0.2 mm / rev

Cutting depth 0.5 mm

The test results are presented in the table.

For comparison, the same table shows the data of conventional oxide-carbide cutting ceramics obtained by hot pressing in graphite molds.

As can be seen from the table, samples manufactured at low pressures according to the proposed method have large dimensions and have higher wear resistance and hardness than analog samples obtained by traditional technology. A tool made from this ceramic exhibits high cutting properties.

Claims (1)

A method of manufacturing a ceramic material, comprising mixing a powder composition of oxides of aluminum, titanium, magnesium, titanium carbide and cubic boron nitride and hot pressing under pressure, characterized in that after mixing the mixture is briquetted under pressure of 0.06-1.5 GPa at room temperature, then subjected to annealing at a temperature of 1200-1400 ° C for 1-5 minutes, and hot pressing is carried out in an environment of either argon or nitrogen, or in vacuum under a pressure of 0.02-0.08 GPa with a holding time of 5-20 minutes, and cubic boron nitride is used with p the particle size is 1-5 μm, and the oxides and carbide of the mixture with a particle size of 0.1-1.0 μm.