RU2748375C1 - Ceramic composite material - Google Patents

Abstract

FIELD: composite material.

SUBSTANCE: invention relates to the production of a composite material with a matrix of zirconium dioxide stabilized in a tetragonal form and aluminum oxide. The material can be used for the manufacture of technical and medical products, in particular, as the basis of cutting tools for high-speed machining of various types of steel, cast iron, non-ferrous metals. Ceramic composite material on the basis of the charge, having a chemical composition (wt. %): 67,0≤ZrO₂≤81,0; 6,3≤Yb₂O₃≤8.3; 10≤Al₂O₃≤25; 0.7≤SrO≤1.7, contains tetragonal zirconium dioxide stabilized by ytterbium (Yb)-TZP cations, aluminum oxide (corundum) and the compound SrAl₁₂O₁₉ (strontium hexaaluminate), with the following phase ratio (vol.%): 78÷87 (Yb)-TZP, 3÷7 SrAl₁₂O₁₉, the rest is corundum. The ceramic composite material has a fine-grained microstructure, in which the long-prismatic grains of the SrAl₁₂O₁₉ phase reach sizes of 250×1500 nm, static bending strength up to 900 MPa, crack resistance K_1c up to 11 MPa·m^1/2, micro-hardness HV of 13.0-13.5 GPa.

EFFECT: creation of a ceramic composite material with a matrix of zirconium dioxide, which has a microstructure with grain sizes not exceeding 1500 nm, with high parameters of crack resistance, bending strength and increased micro-hardness.

1 cl, 1 tbl, 3 ex, 5 dwg

Description

The invention relates to ceramic materials science, obtaining a composite material with a matrix of zirconium dioxide, stabilized in tetragonal form, and aluminum oxide. The material can be used for the manufacture of products for technical and medical purposes, in particular, as a basis for cutting tools for high-speed machining of various types of steel, cast iron, non-ferrous metals.

Ceramics and composite materials based on solid solutions of tetragonal modification of zirconium dioxide T-ZrO ₂ (TZP), which have high parameters of strength, bioinertness and biocompatibility, are used in medicine and technology [Chevalier J. et al. Fourty years after the promise of "Ceramic Steel?": Zirconia Based Composites with a Metal Like Mechanical Behavior // Amer. Ceram. Soc. 2019. V. 103.I. 3.P.1482-1513. doi.org/10.1111/jace.16903], [Garshina A.P., Gropyanov BM, Zaitsev G.P., Semenov S.S. Ceramics for mechanical engineering // M. Nauchtekhlitizdat, 2003. 380 p.], Including for the manufacture of various cutting tools. Critical for the use of materials for these purposes are the value of the brittle fracture resistance parameter of crack resistance and the grain size of the microstructure.

The use of highly dispersed initial powders, which contribute to a decrease in the number of microstructure defects, provides an increase in the strength parameters of ceramics. The introduction of fibers or discrete particles of a certain habit into the ceramic matrix makes it possible to achieve not only an increase in strength, but also the resistance of the material to brittle fracture. A crack that occurs during an impact load in a material, upon colliding with such an obstacle, slows down or stops its growth, energy is absorbed, which determines the slowing down or stopping of the destruction of the material. The introduction of fibers or discrete particles can be carried out mechanically from the outside or created directly in the material "in situ" in the technological process.

Known composite ceramic material, including a matrix, represented by ultrafine powder of zirconium dioxide (ZrO ₂ ), obtained by the plasma-chemical method, and the hardener - reinforcing particles, also obtained by the plasma-chemical method, composition: ZrO ₂ (75-50%) and Al ₂ O ₃ (25 -50%), having the following ratio of matrix and hardener, vol.%: Reinforcing particles - 15-40, matrix (ZrO ₂ ) - the rest.

The size of the reinforcing particles is 0.1-10 microns. The material has high strength parameters [Patent RU 2341494 C2, published 12.2008].

The disadvantage of the known composite material is the complexity of the technological process, obtaining the initial powders in an energy-consuming way. In addition, reinforcing particles have a size of up to 10 microns, which does not allow the material to be used as a base for cutting tools, since the possibility of material destruction is high.

Known material obtained on the basis of commercial powders of aluminum oxide α-Al ₂ O ₃ and 3Y-TZP (tetragonal form of zirconium dioxide, stabilized with 3 mol.% Y ₂ O ₃ ) [N.Yu. Cherkasova, A.A. Bataev, S.V. Veselov, R.I. Kuzmin, N.S. Stukacheva, T.A. Zimoglyadova. Structure and fracture toughness of ceramics based on Al ₂ O ₃ and ZrO ₂ with the addition of SrAl ₁₂ O ₁₉ .

Material letters. 2019.Vol. 9.No.2. S. 179-184 doi.org/10.22226/2410-3535-2019-2-179-184]. Formation of strontium hexaaluminate SrAl₁₂O_nineteen was carried out during the heat treatment of the charge obtained by dispersing the suspension of the initial powders, into which the SrO powder was introduced. Crack resistance of material with a 3Y-TZP matrix (85Mac.%) And containing SrAl₁₂O_nineteen (3 wt.%), The rest is corundum, was less than 6 MPa⋅m^1/2...

The disadvantage of this ceramic material is the volumetric heterogeneity of the material, determined by the method of obtaining a charge from commercial starting powders, which in turn causes low parameters of relative density (about 98% of theoretical) and crack resistance.

Known ceramic material based on powders with a composition of 80 wt. % zirconium dioxide stabilized with 1 mol.% Y ₂ O ₃ and 6 mol.% CeO ₂ (YCe) -TZP, and 10 vol.% Al ₂ O ₃ containing in addition 10 vol.% strontium hexaaluminate obtained separately. All components of the charge are homogenized for 4 hours, followed by heat treatment of the cast samples at a temperature of 800 ° C and sintering at 1500 ° C for 3-72 hours. [Kern F, Gommeringer A. Reinforcement Mechanisms in Yttria-Ceria-Co-Stabilized Zirconia-Alumina-Strontium Hexaaluminate Composite Ceramics // Ceramic Sceince and Technology. 2017.V. 9, No. 1, P. 93-98 doi: 10.4416 / JCST2017-0004].

The disadvantage of the known ceramic material is the complexity of the technological cycle and the long duration of sintering to achieve a densely sintered state (holding at a final temperature of 12 hours), providing a maximum bending strength of 900 MPa.

Known (RF Patent 189195 U1 (11) Published: 15.05.2019. Bull. No. 14) ceramic composite material belonging to the dispersion-hardened class, consisting of a matrix and three types of hardeners, taken in a ratio (wt.%) 50 matrix: 50 hardeners. The matrix is represented by powder of aluminum oxide (Al ₂ O ₃ ) with particle sizes from 0.2 to 1 μm, reinforcement is made by particles of zirconium dioxide (ZrO ₂ ) with dimensions from 0.1 to 0.8 μm and strontium aluminate (SrAl ₁₂ O ₁₉ ), having a lamellar shape with the following dimensions: the length of the plates is from 1 to 5 μm and the width is from 0.2 to 1 μm, and additionally, zirconium dioxide with a particle size of 20-60 nm, which is inside the lamellar phase of strontium aluminate (SrAl ₁₂ O ₁₉ ). The material has high values of strength characteristics.

The disadvantage of the ceramic material of this invention is a complex multistage production chain, including separate synthesis of components, subsequent mixing of a multicomponent suspension with organic additives, granulation in a spray dryer or freeze drying, preliminary sintering at temperatures from 1400 to 1500 ° C, hot isostatic pressing at temperatures from 1400 to 1500 ° C in argon, and then brightening annealing at a temperature of 1200 to 1400 ° C. In addition, the presence of grains up to 5 microns in the microstructure makes it problematic to use it for the base of cutting products in high-speed machining, since the possibility of material destruction due to crumbling of large grains increases.

The closest analogue of the invention in terms of the combination of essential features and the production method is a ceramic composite material of three-phase composition: (Ce) -TZP, corundum (α-Al ₂ O ₃ ) and calcium-cerium hexaaluminate [CeCa] Al ₁₂ O ₁₉ ], presented in the patent RF No. 2710648, publ. 2019.12. The method for producing a charge ensures a homogeneous distribution of components and obtaining initial finely dispersed powders. The ceramic material has a static bending strength of at least 900 MPa, crack resistance K _1s = 12-12.5 ^{MPa,5m 1/2} , microhardness H = 7.5-8.5 GPa.

The disadvantage of this ceramic composite material is the presence in the microstructure of large grains of calcium hexaluminate with a size of at least 3000 × 500 nm, which can initiate their spalling under power loads. Also, the ceramic composite has a low microhardness value (about 8 MPa).

The problem to be solved by the present invention is to create a ceramic material with high strength parameters, fine-grained microstructure, increased microhardness.

The technical result of the invention is the creation of a ceramic composite material with a matrix of zirconium dioxide, which has a microstructure with grain sizes not exceeding 1500 nm, with high parameters of crack resistance, bending strength and increased microhardness.

The technical result is achieved by the fact that a ceramic composite material based on a charge having a chemical composition (wt.%): 67.0≤ZrO ₂ ≤81.0; 6.3 Yb ₂ O ₃ 8.3; 10≤Al ₂ O ₃ ≤25; 0.7≤SrO≤1.7 contains tetragonal zirconia stabilized with ytterbium (Yb) -TZP cations, aluminum oxide (corundum) and strontium hexaaluminate-SrAl ₁₂ O ₁₉ , with the following phase ratio (vol.%): 78 ÷ 87 (Yb) -TZP, 3 ÷ 7 SrAl ₁₂ O ₁₉ , the rest is corundum.

The essence of the invention is as follows.

, микротвердость HV=13,0-13,5 ГПа. Свойства материалов по прототипу и изобретению, представлены в таблице 1.The claimed chemical composition and the method used for preparing the charge, which ensures a homogeneous distribution of the components synthesized in the nanoscale state, determine the formation, during sintering, carried out at temperatures of 1570-1600 ° C, of a composite material of a three-phase composition with a fine-grained microstructure, having high strength properties and increased hardness. The claimed ceramic material has a static bending strength of at least 900 MPa, K _1c = 11 MPa МПm

, microhardness HV = 13.0-13.5 GPa. The properties of materials according to the prototype and the invention are presented in table 1.

Deviations from the claimed content of the components affect the strength characteristics. It was experimentally established that an increase in the SrO content above 1.7% leads to an increase in the content of the SrAl ₁₂ O ₁₉ phase, which is accompanied by an increase in the porosity of the material, and, accordingly, a decrease in the mechanical characteristics of the composite. An excess of the Al ₂ O ₃ content above 25% does not allow reaching the dense-sintered state of the material at a temperature of 1600 ° C. Sintering at temperatures below 1570 ° C leads to the production of specimens with open porosity, and exceeding the temperature of 1600 ° C leads to recrystallization and the appearance of closed porosity, the first and second causes a decrease in the strength of ceramic specimens.

, микротвердостью HV=13,0-13,5 ГПа. Достигнутые параметры позволяют использовать данную керамику в качестве конструкционного материала, в частности, для изготовления режущего инструмента.The proposed technical solution makes it possible to obtain a ceramic composite material having a density of 99.3 ÷ 99.5% of the theoretical, a fine-grained microstructure characterized by the following grain sizes in accordance with the phase composition: globular (Yb) -TZP ∅ 300 nm, rhombohedral Al ₂ O ₃ up to 0 700 nm and long-prism grains SrAl ₁₂ O ₁₉ 250 × 1500. The material is characterized by: strength in static bending 900 MPa, crack resistance K _1s = 11 MPa⋅m

, microhardness HV = 13.0-13.5 GPa. The achieved parameters make it possible to use this ceramics as a structural material, in particular, for the manufacture of cutting tools.

The invention is illustrated by 3 examples, 5 figures and 1 table.

Examples of specific production of the claimed ceramic material are given for the synthesis of 100 g of a charge.

Example 1

To obtain a composite material containing (wt.%): ZrO ₂ - 81.0; Yb ₂ O ₃ 8.0; Al ₂ O ₃ - 10.2; SrO - 0.8 to a mixture of 800 ml of a 17% aqueous solution of ammonia and 100 ml of a 0.1% aqueous solution of polyvinylpyrrolidone add a mixture of aqueous solutions of salts (concentration 1 mol / l): 657 ml of zirconium oxychloride, 41 ml of ytterbium nitrate, 200 ml of aluminum nitrate, 7.7 ml of strontium nitrate. Precipitation is carried out with constant stirring, setting the stirrer speed to 400 rpm, for 1 hour, maintaining the acidity of the system within the pH range of 9.4-9.7. The gel-like precipitate is filtered off on a Buchner funnel, washed with a five-fold volume of distilled water and dried in ethanol at a temperature of 180 ° C for 4 hours. The obtained hydrogels are heat treated in a muffle furnace at a temperature of 950 ° C with holding for 1 hour, the temperature rise is carried out at a rate of 10 ° C / min. Disaggregation is carried out in ethanol for 15 minutes, after which the powder is dried in an oven at 120 ° C. The specific surface area measured by the BET method was 30 m ² / g. The powders are compacted by semi-dry pressing at a specific pressure of 200 MPa. Sintering is carried out in furnaces with chromite-lanthanum heaters in air with continuous heating at a rate of 5 ° C / min to a final temperature of 1580 ° C with a holding for 2 hours. The relative density of the ceramics, determined by the method of hydrostatic weighing, was 99.5% of the theoretical. The phase composition of the ceramic composite material contains corundum, a solid solution based on tetragonal zirconium dioxide, and strontium hexaaluminate. The latter is determined in the microstructure of the material in an amount of at least 3 vol.%, Which is illustrated in Fig. 5a.

Example 2

To obtain a composite material containing (wt.%): ZrO ₂ - 75.3; Yb ₂ O ₃ - 7.6; Al ₂ O ₃ - 16.3; SrO 0.8; to a mixture of 880 ml of a 17% aqueous solution of ammonia and 110 ml of a 0.1% aqueous solution of polyvinylpyrrolidone add a mixture of aqueous solutions of salts (concentration 1 mol / l): 611 ml of zirconium oxychloride, 39 ml of ytterbium nitrate, 320 ml of aluminum nitrate, 7 , 7 ml of strontium nitrate. Precipitation is carried out with constant stirring, setting the stirrer speed to 400 rpm, for 1 hour, maintaining the acidity of the system within the pH range of 9.4-9.7. The gel-like precipitate is filtered off on a Buchner funnel, washed with a five-fold volume of distilled water and dried in ethanol at a temperature of 180 ° C for 4 hours. The obtained hydrogels are heat treated in a muffle furnace at a temperature of 950 ° C with holding for 1 hour, the temperature rise is carried out at a rate of 10 ° C / min. Disaggregation is carried out in ethanol for 15 minutes, after which the powder is dried in an oven at 120 ° C. The specific surface area measured by the BET method was 30 m ² / g. The powders are compacted by semi-dry pressing at a specific pressure of 200 MPa. Sintering is carried out in furnaces with chromium-lanthanum heaters in an air environment with continuous heating at a rate of 5 ° C / min to a final temperature of 1590 ° C with holding for 2 hours. The relative density of ceramics, determined by the method of hydrostatic weighing, was 99.4% of the theoretical. The phase composition of the ceramic composite material contains corundum, a solid solution based on tetragonal zirconium dioxide, and strontium hexaaluminate (Fig. 3). The latter is determined in the microstructure of the material in an amount of at least 4 vol.%, Which is illustrated in Fig. 5 B.

Example 3

To obtain a composite material containing (wt.%): ZrO ₂ - 74.6; Yb ₂ O ₃ - 7.4; Al ₂ O ₃ - 16.4; SrO - l, 6; to a mixture of 880 ml of a 17% aqueous solution of ammonia and 110 ml of a 0.1% aqueous solution of polyvinylpyrrolidone add a mixture of aqueous solutions of salts (concentration 1 mol / l), taken in the following volumes: 605 ml of zirconium oxychloride, 38 ml of ytterbium nitrate, 322 ml of aluminum nitrate, 15.4 ml of strontium nitrate. Precipitation is carried out with constant stirring, setting the stirrer speed to 400 rpm, for 1 hour, maintaining the acidity of the system within the pH range of 9.4-9.7. The gel-like precipitate is filtered off on a Buchner funnel, washed with a five-fold volume of distilled water and dried in ethanol at a temperature of 180 ° C for 4 hours. The obtained hydrogels are heat treated in a muffle furnace at a temperature of 950 ° C with holding for 1 hour, the temperature rise is carried out at a rate of 10 ° C / min. Disaggregation is carried out in ethanol for 15 minutes, after which the powder is dried in an oven at 120 ° C. The specific surface area measured by the BET method was 32 m ² / g. The powders are compacted by semi-dry pressing at a specific pressure of 200 MPa. Sintering is carried out in furnaces with chromite-lanthanum heaters in air with continuous heating at a rate of 5 ° C / min with holding at a final temperature of 1590 ° C for 2 hours. The relative density of ceramics, determined by the method of hydrostatic weighing, was 99.4% of the theoretical. The phase composition of the ceramic composite material contains corundum, a solid solution based on tetragonal zirconium dioxide, and strontium hexaaluminate (Fig. 3); strontium hexaaluminate is present in an amount of at least 7 vol%, which is illustrated in Fig. 5c.

Table 1 shows comparative data on the relative density (ρ rel.), Microhardness (H), crack resistance (K1c) and static bending strength (σ) and the maximum grain size of the microstructure of the prototype and the claimed ceramic material.

In fig. 1 shows as an example a diffractogram of an initial ceramic powder corresponding to example (2) after thermal treatment of xerogels at a temperature of 950 ° C, confirming the formation of one phase of a solid solution based on zirconium dioxide of a pseudocubic structure and the absence of amorphized phases.

Designation: F - solid solution based on zirconium dioxide stabilized with ytterbium cations.

In fig. 2 shows as an example a powder diffractogram corresponding to example (2) after heat treatment at a temperature of 1550 ° C, confirming the formation of a predominant solid solution phase based on tetragonal zirconia and, in the form of trace amounts, corundum phases and strontium hexaaluminate SrAl ₁₂ O ₁₉ ...

Designation: T - solid solution based on tetragonal zirconium dioxide stabilized by ytterbium cations, K-corundum.

In fig. 3 shows fragments of diffraction patterns of samples corresponding to examples No. 2 and 3, after heat treatment at a temperature of 1590 ° C, in the region of the main reflections of a) corundum, b) SrAl ₁₂ O ₁₉ compounds.

Designations: T - solid solution based on tetragonal zirconium dioxide stabilized by ytterbium cations H - strontium hexaaluminate K - corundum.

In fig. 4 shows electronic images of the surface a) of the inventive ceramic material containing 24 wt. % Al ₂ O ₃ and b) of the prototype, which illustrate the different formation of the grain microstructure.

In fig. 5 shows electronic images of the surface of ceramic materials corresponding to examples: a) 1, b) 2 and c) 3.

Claims (1)

Ceramic composite material based on a charge having a chemical composition (wt.%): 67.0≤ZrO ₂ ≤81.0; 6.3 Yb ₂ O ₃ 8.3; 10≤Al ₂ O ₃ ≤25; 0.7≤SrO≤1.7, contains tetragonal zirconia stabilized with ytterbium cations (Yb) -TZP, and alumina (corundum), characterized in that it contains the compound SrAl ₁₂ O ₁₉ (strontium hexaaluminate), with the following phase ratio (vol.%): 78 ÷ 87 (Yb) -TZP, 3 ÷ 7 SrAl ₁₂ O ₁₉ , the rest is corundum.

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