EP1656331A1

EP1656331A1 - Material based on sialon's

Info

Publication number: EP1656331A1
Application number: EP04763870A
Authority: EP
Inventors: Bernd Bitterlich; Kilian Friederich; Ulrich Mowlai
Original assignee: Geramtec AG Innovative Ceramic Engineering; Ceramtec GmbH
Current assignee: Ceramtec GmbH
Priority date: 2003-08-07
Filing date: 2004-08-06
Publication date: 2006-05-17
Also published as: BRPI0413423A; CA2534321A1; CA2534321C; US7514383B2; JP2007501759A; US20070010392A1; KR101181548B1; WO2005016847A8; WO2005016847A1; JP5221875B2; KR20060125680A

Abstract

Known Si3N4 and SiAlON cutting materials become, at the beginning, rounded very quickly on the cutting edge during usual long continuous cuts in gray cast iron (GG) which is described as initial wear. The invention thus provides that the raw material mixture of the material comprised of: component A, an alpha/beta SiAlON, and; component B, a hard material, has a composition consisting of 70 to 97 % by volume of component A and 3 to 30 % by volume of component B.

Description

Material based on SiAlONs

The present invention relates to a material based on SiAlONs, its production and use.

Known Si ₃ N and SiAlON cutting materials initially round very quickly at the cutting edge in the usual long continuous cuts in gray cast iron (GG), which is referred to as initial wear.

It is therefore the object of the present invention to eliminate this disadvantage of the known cutting materials.

This object is achieved according to the invention by providing a material which consists of components A and B, where A stands for an alpha / beta-SiAlON and B for a hard material. The material according to the invention contains 70 to 97% by volume, preferably 80 to 95% by volume, particularly preferably 84 to 91% by volume of component A and 3 to 30% by volume, preferably 5 to 20% by volume, particularly preferably 9 to 16% by volume Component B.

The raw material mixture of component A used according to the invention consists of the main constituents Si ₃ N ₄ , AIN, further additives such as Al ₂ O ₃ , Y ₂ O ₃ , Sc ₂ O ₃ , rare earth oxides and small amounts of compounds which Li , Ca, Mg, Sr included. Comparable mixtures are already known from DE 35 11 734 A1. The material according to the invention arises from the above-mentioned raw material mixture and the added hard materials during a heat treatment at temperatures from 1800 to 2000 ° C. and holding times at the maximum temperature from 0.5 to 5 hours.

Component A consists of alpha and beta SiAlON as well as an amorphous or partially crystalline grain boundary phase. In the sintered state of the material, the SiAlON phase of the sintered body inside consists of an alpha-SiAlON content of 10 to 90% by volume, preferably 12 to 60% by volume, particularly preferably 15 to 50 vol% and a proportion of beta-SiAlON 90 to 10 vol%, preferably 88 to 40 vol%, particularly preferably 85 to 50 vol% ^' beta-SiAlON. The proportion of alpha and beta SiAlON is determined on the basis of X-ray diffractometric images (according to Gazzara and Messier, J. Am. Ceram. Soc. Bull. 56 (1977)).

The grain boundary phase content is less than 10% by volume, preferably less than 5% by volume. The grain boundary phase can be amorphous, but should preferably be partially crystalline. As is known, the composition of A inside a sintered body can be varied by the production parameters such as, for example, the composition of the powder mixture, the sintering conditions in the furnace, the crucible material, the type of gas, the temperature and the sintering time. In component A there can be a gradient between the sintered body surface and the inside, so that the so-called as fired surface contains up to 100% alpha-SiAlON.

A gradient in component A can arise under certain conditions if the surface of the sintered body cools faster than the inside or the chemical composition of the surface is changed by reactions with the atmosphere. An alpha-SiAlON-rich surface leads to a hard outer layer with a tough core.

As hard materials, component B, for example SiC, Ti (C, N), TiC, TiN, carbides and / or nitrides of the elements of groups IVb, Vb and VIb of the periodic table (PSE) as well as scandium carbide and / or scandium oxyarbide or mixtures of the listed hard materials are used. Hard materials are stored inter- and / or intragranularly during the heat treatment, ie both between and in the SiAlON grains and do not change during the heat treatment. The size of the hard material particles used should therefore not exceed the size of the other structural components, alpha- and beta-SiAlON grains, since the hard materials would otherwise impair the mechanical properties of the material according to the invention. That means the middle one The grain size of the hard materials should be less than 30 μm, preferably less than 15 μm, particularly preferably less than 5 μm. The hard material particles can be globular grains, platelets or whiskers; globular grains are particularly preferred.

The maximum size of the alpha and beta SiAlON grains should be less than 90 μm, preferably less than 65 μm, particularly preferably less than 50 μm. While small grain sizes are usually aimed for in the known materials, it has surprisingly been found in the material according to the invention that the application properties are influenced only insignificantly by the grain size.

Thermal treatment to crystallize the amorphous grain boundary phase is possible and is even preferred. As is known, depending on the production parameters such as the composition of the powder mixture and sintering conditions such as temperature, gas composition, gas pressure, time course, insulation and crucible material, crystalline phases, particularly preferably aluminum-containing melilite or disilicate.

The advantages of the material according to the invention over the known materials are its higher hardness with> 1550 HV10 and thus its higher wear resistance.

Furthermore, the material according to the invention has a higher hot hardness, i.e. a higher wear resistance even at high cutting speeds at which the temperature at the cutting edge rises.

Furthermore, the chemical reactions of the glass phase with the material of the workpiece to be machined are significantly lower, even at high cutting speeds. The material according to the invention can be coated with the known wear-reducing layers such as, for example, Al ₂ O ₃ , TiN or TiC, which increases the wear resistance.

The material according to the invention can be produced by methods known per se, as are also used in the production of high-performance ceramic components, in particular SiAlON materials, by powder mixing, shaping, sintering and finishing by grinding.

The gas atmosphere during sintering should be inert and can be N ₂ or a mixture of N ₂ and other inert gases such as Ar. The table below shows exemplary embodiments of compositions of the material according to the invention. The high hardness is remarkable in each case.

Table: Composition and properties of the exemplary embodiments

Sample weight in kg Example 1 Example 2 Example 3 Example 4 Example 5

Si ₃ N ₄ 5.66 5.66 5.35 5.34 4.90

Y ₂ O ₃ 0.32 0.32 0.30 0.30 0.27

AIN 0.29 0.29 0.27 0.27 0.25

MgO 0.01 0.01 0.01 0.01 0.01

AI ₂ O ₃ 0.03 0.03 0.03 0.03 0.03

SiC 0.69 0.69 1, 04 - -

Ti (C, N) - - - 1, 05 1, 53

Max.

Sintertemp. 1940 ° C 1800 ° C 1800 ° C 1800 ° C 1900 ° C

Holding time 3 h 1 h 1 h 1 h 3 h

Final density> 99.9% th. > 99.9% th. > 99.9% th. 99.9% th. 99.9% th.

Alpha-SiAlON 28% 55% 58% 54% 31% regarding alpha + beta inside the sample Hard material - 10 vol% SiC 10 vol% SiC 15 vol% SiC 10 vol% 15 vol%

TiCN content TiCN

Color gray-green gray-green gray-green gray-brown gray-brown

Hardness (HV10) 1730 1810 1820 1810 1790 At final density: th. = theoretical density While the known Si N and SiAlON cutting materials are light gray to dark gray-black, the material according to the invention is gray-green when SiC is added and gray-brown when Ti (C, N) is added. As a cutting material, the material according to the invention surprisingly does not show the disadvantages of the known cutting materials, the initial wear, when machining gray cast iron with the usual long continuous cuts, but retains a sharp edge until the end of its service life. Furthermore, it was recognized that the material according to the invention surprisingly also proves advantageous in the case of so-called "notch wear": When machining gray cast iron with particularly aggressive cast skin, a deep notch is formed after a short time in the cutting materials known to date. This wear is mainly caused by chemical wear, ie chemical reactions between the material of the cutting tool and the material of the workpiece, whereas the material according to the invention shows such wear only after a considerably longer service life.

Two diagrams, FIG. 1 and FIG. 2, show the advantage of the material according to the invention, “new cutting material”, over a material made of silicon nitride, “reference”. The wear width on the main cutting edge, “VBH”, is indicated in FIG. 1 as a function of the number of cuts. A brake disc made of GG15 was rotated at a cutting speed (peripheral speed of the rotating part on the cutting edge) “vc = 1000 m / min” with a Feed "f = 0.5 mm / rev" and an infeed (depth of cut) "ap = 2.0 mm". 2 shows the wear width of the corner, “VBE”, the notch wear when turning alloy gray cast iron, GG25, with cast skin depending on the number of cuts, also in comparison to a cutting tool made of silicon nitride Cutting speed (peripheral speed of the turned part on the cutting edge) of "vc = 800 m / min" with a feed "f = 0.5 mm / rev" and an infeed (depth of cut) "ap = 2.0 mm".

In addition to the use as a cutting material, applications in other areas of application are also conceivable, where high wear resistance is important and thermal and chemical stresses on the material may also occur. For example, an advantageous use of the material according to the invention as a sealing ring is conceivable, or use in fuel and coolant pumps, in compressors, turbochargers, heat exchangers and air conditioning systems.

Claims

claims

1. Material based on SiAlON, characterized in that the raw material mixture of the material consists of components A, an alpha / beta-SiAlON, and B, a hard material, in the composition of 70 to 97 vol%, preferably 80 to 95 Vol%, particularly preferably 84 to 91 vol% of component A and 3 to 30 vol%, preferably 5 to 20 vol%, particularly preferably 9 to 16 vol% of component B.

2. Material according to claim 1, characterized in that component A consists of alpha and beta SiAlON and an amorphous or partially crystalline grain boundary phase.

3. Material according to claim 1 or 2, characterized in that in the sintered state inside the sintered body the proportion of alpha-SiAlON with respect to the entire SiAlON phase 10 to 90 vol%, preferably 12 to 60 vol%, particularly preferably 15 to 50 vol% and the proportion of beta-SiAlON 90 to 10 vol%, preferably 88 to 40 vol%, particularly preferably 85 to 50 vol.

4. Material according to one of claims 1 to 3, characterized in that the content of grain boundary phase is less than 10 vol%, preferably less than 5 vol% and that the grain boundary phase is amorphous.

5. Material according to one of claims 1 to 3, characterized in that the content of grain boundary phase is less than 10 vol%, preferably less than 5 vol% and that the grain boundary phase is partially crystalline.

6. Material according to claim 5, characterized in that the grain boundary phases contain crystalline phases, preferably aluminum-containing melilite or disilicate.

7. Material according to one of claims 1 to 6, characterized in that a sintered body of the material has an alpha-SiAlON gradient falling from the outside inwards and that the alpha-SiAlON content of the as-fired surface is up to 100% can.

8. Material according to one of claims 1 to 7, characterized in that the maximum size of the alpha and beta-SiAlON grains is less than 90μm, preferably less than 65μm, particularly preferably less than 50μm.

9. Material according to one of claims 1 to 8, characterized in that as hard materials, component B, SiC, Ti (C, N), TiC, TiN, carbides and / or nitrides of the elements of groups IVb, Vb and VIb of the periodic table (PSE) as well as scandium carbide and / or scandium oxyarbide or mixtures of the hard materials listed, which have an unchanged state after sintering.

10. Material according to one of claims 1 to 9, characterized in that the hard materials inter- and / or intragranular, i.e. are embedded between as well as in the SiAlON grains.

11. Material according to one of claims 1 to 10, characterized in that the average grain size of the hard materials is less than 30μm, preferably less than 15μm, particularly preferably less than 5μm.

12. Material according to claim 11, characterized in that the hard material grains are globular, needle or plate-shaped.

13. Material according to one of claims 1 to 12, characterized in that its hardness is> 1550 HV 10.

14. Material according to one of claims 1 to 13, characterized in that it is coated with wear-reducing layers such as Al ₂ O ₃ , TiN or TiC.

15. A method for producing a material based on SiAlONs according to one of claims 1 to 14 by powder mixing, shaping, sintering and grinding, as is used in the production of high-performance ceramic components, in particular from SiAlON materials.

16. The method according to claim 15, characterized in that component A is formed during a heat treatment at temperatures of 1800 to 2000 ° C and holding times at the maximum temperature of 0.5 to 5 hours.

17. The method according to claim 15 or 16, characterized in that the gas atmosphere is inert during sintering and contains N ₂ or a mixture of N ₂ and other inert gases, in particular argon.

18. Material according to one of claims 1 to 14, produced by a method of claims 15 to 17, for use as a cutting material.

19. Material according to one of claims 1 to 14, produced by a method of claims 15 to 17, for use as a cutting material for processing gray cast iron.

20. Material according to one of claims 1 to 14, produced by a method of claims 15 to 17, for use as a sealing ring.

1. Material according to one of claims 1 to 14, produced by a method of claims 15 to 17, for use in fuel and coolant pumps, compressors, turbochargers, heat exchangers and air conditioning systems.