CN102173802B - In situ (TiB)2+SiC)/Ti3SiC2Complex phase ceramic material and preparation method thereof - Google Patents

Abstract

The invention relates to an in-situ (TiB ₂ +SiC)/Ti ₃ SiC ₂ composite ceramic material, which is characterized in that it consists of a layered Ti ₃ SiC ₂ matrix and two reinforcing phases of columnar TiB ₂ and granular SiC; wherein _TiB2 accounts for 13-15% of the total volume of the composite ceramic material, and SiC accounts for 5-15% of the total volume of the composite ceramic material. The preparation steps are as follows: the raw materials _TiH2 powder, Si powder, TiC powder, _B4C powder and Al powder are prepared in a molar ratio of (0.9-1.3): (1): (1.4-1.6): (0.15-2.1) : (0.13～0.16) Weighing, mixing the raw materials and putting them into graphite molds for cold pressing, then hot pressing and sintering in a graphite resistance furnace with a protective atmosphere. The invention has simple process and excellent material performance.

Description

A kind of in-situ (TiB2+SiC)/Ti3SiC2 composite ceramic material and its preparation method

Technical field:

The invention relates to a ceramic-based composite material and a preparation method thereof, specifically a _{Ti3SiC2 -} based multi-phase ceramic material reinforced by columnar _TiB2 and granular SiC by in-situ hot-pressing sintering and a preparation method thereof, namely a In-situ (TiB ₂ +SiC)/Ti ₃ SiC ₂ composite ceramic material and its preparation method.

Background technique:

Ti ₃ SiC ₂ is a representative of the ternary layered machinable ceramic MAX, which combines the characteristics, structure and functional properties of metal and ceramics, and has the characteristics of low density, high modulus, thermal shock resistance, good electrical and thermal conductivity, etc., and at the same time It also has a lower friction coefficient and better self-lubricating properties than traditional lubricating materials graphite and _MoS2 , and is very promising to become a new generation of high-temperature structural materials, electrode materials in molten metals, machinable ceramic materials, self-lubricating materials and Electrode brush material.

However, Ti ₃ SiC ₂ has low hardness and creep strength at room temperature, poor wear resistance and oxidation resistance, which severely limit its application. Complex phase and self-toughening structure are effective ways to improve the mechanical properties of materials and realize reinforcement and toughening. At present, the properties of Ti ₃ SiC ₂ have been improved by introducing Al ₂ O ₃ , TiC, SiC, c-BN, TiB ₂ , ZrO ₂ etc. as reinforcing phases (Hu CF, Zhou Y C, Bao Y W, Wan D T.Al ₂ O ₃ enhances the tribological properties of Ti ₃ SiC ₂ composite materials[J]. Journal of American Ceramic Society, 2006, 89(11): 3456-3461; Zhang J F, Wang L J, Jiang W, Chen L D. Effect of TiC content on discharge Influence of plasma in situ synthesis on microstructure and properties of Ti ₃ SiC ₂ -TiC composite materials[J]. Materials Science and Engineering A, 2008, 487(1-2): 137-143; Zhang J F, Wang L J, Jiang W, Chen L D. Preparation of Ti ₃ SiC ₂ -SiC Nanocomposite Materials by Discharge Plasma [J]. Materials Letters, 2007, 56(3): 241-244; Benko E, Klimczyk P, Mackiewicz S, BarrT L , Piskorska E.cBN-Ti ₃ SiC ₂ composite materials[J]. Properties and applications of diamond-like films, 2004, 13(3): 521-525; Zhou W B, Mei B C, Zhu J Q. Principle of hot pressing method In-situ synthesis of Ti ₃ SiC ₂ /TiB ₂ composite materials[J]. Journal of Wuhan University of Technology, Natural Science Edition, 2008, 23(6): 863-865; Shi S L, Pan W. Preparation of 3Y-TZP toughened by discharge plasma method Ti ₃ SiC ₂ [J].Materials Science and Engineering, 2007, 447(1-2): 303-306), but a strong and tough phase is usually used, the reinforcing and toughening mechanism is single, and the reinforcing and toughening effect is limited . Chen et al (Chen J X, Li J L, Zhou Y C. In situ synthesis of Ti ₃ AlC ₂ /TiC-Al ₂ O ₃ composite materials in TiO ₂ -Al-C system[J]. Materials Science and Technology, 2006, 22 (4): 455-458) During the preparation of Ti ₃ AlC ₂ -Al ₂ O ₃ composites by combustion reaction of 3TiO ₂ -5Al-2C system, Ti ₃ AlC ₂ /SiC-Al ₂ O ₃ composites were unexpectedly produced , the material exhibits higher hardness and strength than pure _Ti3AlC2 ceramics, but _a slight decrease in fracture toughness. Zan et al. (Zan Q F, Dang L M, Wang C, Wang C A, _Huang Y. Enhancement of mechanical properties _{of Al2O3} / _Ti3SiC2 composite ceramics by introducing SiC whiskers into layered _Al2O3 [ _J ]. Ceramics International, 2007, 33: 385-388) introduced SiC whiskers into the Al ₂ O ₃ layer of multilayer ceramics Al ₂ O ₃ /Ti ₃ SiC ₂ , due to the synergistic effect of multilayer structure toughening and whisker toughening , the material exhibits excellent mechanical properties: the bending strength is 688MPa, and the work of fracture is 2583J·m ^-2 , but the reinforcement phase is introduced by mechanical mixing, and the preparation process is relatively complicated. Gu Wei et al. (Gu Wei, Yang Jian, Qiu Tai, Zhu Shemin in situ synthesis of (TiB ₂ +TiC)/Ti ₃ SiC ₂ composites and their properties research [J]. Journal of Inorganic Materials, 2010, 25(10): 1-6) The comprehensive performance of the material is improved by introducing TiB ₂ and TiC two-phase composite reinforcement into the Ti ₃ SiC ₂ matrix: the flexural strength and fracture toughness are higher than 700MPa and 9MPa·m ^1/2 respectively. The in-situ synthesized (TiB ₂ +TiC)/Ti ₃ SiC ₂ composite material has a uniform microstructure, fine grains, and no pollution at the particle interface of the reinforcing phase, but the microhardness and oxidation resistance of the composite material still need to be improved.

Invention content:

The invention provides an in-situ (TiB ₂ +SiC)/Ti ₃ SiC ₂ composite ceramic material with low cost, good mechanical properties, simple process and easy control of conditions and a preparation method thereof. The two strengthening phases of columnar TiB ₂ and granular SiC are strengthened synergistically, and the bending strength and fracture toughness of the material are significantly improved, thereby overcoming the problems existing in the prior art.

The technical solution of the present invention is to prepare (TiB ₂ +SiC)/Ti ₃ SiC ₂ multiphase ceramic material by in-situ synthesis method. The basic principle is to use Al as a sintering aid, and TiH ₂ decomposes at high temperature to produce Ti , and then Ti reacts with Si and TiC to form a Ti ₃ SiC ₂ matrix. At the same time, Ti also reacts with B ₄ C and Si to form a joint reinforcement phase of TiB ₂ and SiC with different shapes and different reinforcement mechanisms in situ, thus preparing in one step (TiB ₂ +SiC)/Ti ₃ SiC ₂ material.

The specific technical solution of the present invention is: an in-situ (TiB ₂ +SiC)/Ti ₃ SiC ₂ composite ceramic material, which is characterized in that it consists of layered Ti ₃ SiC ₂ matrix and columnar TiB ₂ and granular SiC. Reinforced phase composition, in which TiB ₂ accounts for 13-15% of the volume of the composite ceramic material, and SiC accounts for 5-15% of the volume of the composite ceramic material.

The present invention also provides a method for preparing the above-mentioned composite material, the specific steps of which are: raw material TiH ₂ powder, Si powder, TiC powder, B ₄ C powder and Al powder in a molar ratio of (0.9-1.3): (1) : (1.4～1.6): (0.15～2.1): (0.13～0.16) Weighing; the raw materials are mechanically mixed and put into a graphite mold with a protective coating on the surface for cold pressing. Graphite resistance furnace hot pressing sintering.

Preferably, the particle size of the TiH ₂ powder and Si powder is 300 mesh; the particle size of the B ₄ C powder is 3-10 μm; the particle size of the TiC powder is 1-1.5 μm; the particle size of the Al powder is 200 mesh .

Preferably, the heating rate during the sintering process is 10-50° C./min; the sintering temperature is 1350-1500° C.; the sintering time is 1.5-2 hours; the sintering pressure is 22-25 MPa.

In the present invention, it is preferred that the temperature is first raised to 800-900°C during the sintering process, and the temperature is pre-heated for 50-60 minutes without pressure. After reaching the sintering temperature, pressurize to the holding pressure at a rate of 2-3 MPa every 3-5 minutes. Preferably the protective atmosphere during sintering is an inert gas, more preferably argon.

Beneficial effect:

1. Using TiH ₂ as the raw material to provide the Ti source, it will be completely decomposed before 900°C during the heating process to produce pure, fine and highly active Ti powder, which avoids the traditional use of Ti powder as the titanium source, and the Ti powder cannot be used directly. Avoided Oxidation Detrimental Effects on Material Composition, Structure, and Properties. At the same time, the price of TiH ₂ is lower than that of Ti powder and it is easy to store.

2. Due to the good electrical conductivity of TiB ₂ , the prepared (TiB2+SiC)/Ti ₃ SiC ₂ composite material still maintains good electrical conductivity and can be used as an electrode or brush material.

3. Using Al as a sintering aid, due to the low melting point of Al, the liquid phase formed at high temperature accelerates the diffusion of Ti and Si atoms, accelerates the reaction synthesis of Ti ₃ SiC ₂ and improves the purity of the product.

4. The prepared (TiB ₂ +SiC)/Ti ₃ SiC ₂ composite material has a uniform microstructure and fine grains. It is composed of layered Ti ₃ SiC ₂ , columnar TiB ₂ and granular SiC, and the particle interface of the reinforcing phase is free of pollution , The interaction between the two strong and tough phases of columnar TiB ₂ and granular SiC, and the two strengthening and toughening mechanisms are synergistically coupled to each other, so that the flexural strength and fracture toughness of the material are significantly improved.

5. Due to the high hardness of TiB ₂ and SiC, the prepared (TiB ₂ +SiC)/Ti ₃ SiC ₂ composite material has excellent properties of high hardness and good wear resistance.

6. Utilizing the Si, Al, and B elements in the material, the (TiB ₂ +SiC)/Ti ₃ SiC ₂ composite material will form a dense borosilicate (aluminum) passivation layer on the surface during oxidation, thereby improving Oxidation resistance of the material.

Description of drawings:

Figure 1 is the XRD spectrum of the (TiB ₂ +SiC)/Ti ₃ SiC ₂ composite material obtained in Example 1, where ★ represents Ti ₃ SiC ₂ , ● points represent TiB ₂ , and ◆ represents SiC;

Fig. 2 is a scanning electron micrograph of the fracture of the composite (TiB ₂ +SiC)/Ti ₃ SiC ₂ composite obtained in Example 1.

Detailed ways:

Example 1:

Weigh the raw material TiH ₂ powder (300 mesh) according to the molar ratio n(TiH ₂ ):n(Si):n(TiC):n(B ₄ C):n(Al)=0.9194:1:1.5012:0.1833:0.1369 , Si powder (300 mesh), TiC powder (1.5 μm), B ₄ C powder (5 μm) and Al powder (200 mesh), dry mixed in a polyethylene tank for 24 hours, and then placed in a graphite mold coated with BN Cold press molding, hot pressing sintering in argon atmosphere, at a rate of 30 ° C / min to 850 ° C for 55 minutes without pressure pre-heating, then at a rate of 30 ° C / min to 1500 ° C, after reaching the sintering temperature, every The rate of pressurization of 3MPa is increased to 22MPa in 3 minutes, and the holding time is 1.5h. The density of the obtained bulk material reaches 99.7%, in which _TiB2 accounts for 15% of the volume of the composite ceramic material, and SiC accounts for 10% of the volume of the composite ceramic material; the three-point bending strength of the material tested on the universal testing machine is greater than 780MPa, The fracture toughness of the material measured by the unilateral notched beam method is greater than 8.4MPa·m ^1/2 . XRD analysis was performed on the prepared material, as shown in Figure 1, the material was composed of Ti ₃ SiC ₂ , TiB ₂ and SiC. SEM analysis was performed on the fracture surface of the material. As shown in Figure 2, the microstructure of the material is uniform, and the layered Ti ₃ SiC ₂ , columnar TiB ₂ and granular SiC grains are clearly visible, and the grains are fine.

Example 2:

Weigh the raw material TiH ₂ powder (300 mesh) according to the molar ratio n(TiH ₂ ):n(Si):n(TiC):n(B ₄ C):n(Al)=1.2003:1:1.5994:0.2003:0.15994 , Si powder (300 mesh), TiC powder (1.5 μm), B ₄ C powder (5 μm) and Al powder (-200 mesh), dry mixed in a polyethylene tank for 24 hours and then placed in a graphite mold coated with BN Cold press forming, hot pressing sintering in argon atmosphere, at a rate of 50 °C/min to 900 °C for 50 minutes without pressure pre-heating, then at a rate of 20 °C/min to 1450 °C, after reaching the sintering temperature, every Boost the pressure to 24MPa at a rate of 2.5MPa in 5 minutes, and the holding time is 1.8h. The density of the obtained bulk material reaches 99.7%, in which _TiB2 accounts for 14.5% of the volume of the composite ceramic material, and SiC accounts for 5% of the volume of the composite ceramic material; the three-point bending strength of the material tested on the universal testing machine is greater than 770MPa, The fracture toughness of the material measured by the unilateral notched beam method is greater than 7.4MPa·m ^1/2 .

Example 3:

Weigh the raw material TiH ₂ powder (300 mesh) according to the molar ratio n(TiH ₂ ):n(Si):n(TiC):n(B ₄ C):n(Al)=1.1998:1:1.6011:0.2005:0.15994 , Si powder (300 mesh), TiC powder (1 μm), B ₄ C powder (10 μm) and Al powder (200 mesh), dry mixed in a polyethylene tank for 24 hours, then cold pressed in a graphite mold coated with BN Molding, hot-pressing and sintering in argon atmosphere, rising to 900°C at a rate of 30°C/min for 60 minutes without pressure, then raising the temperature to 1400°C at a rate of 50°C/min, after reaching the sintering temperature, every 4 minutes The rate of pressurization is 3MPa to increase to 25MPa, and the holding time is 2h. The density of the obtained bulk material reaches 99.6%, in which _TiB2 accounts for 14.5% of the volume of the composite ceramic material, and SiC accounts for 5% of the volume of the composite ceramic material; the three-point bending strength of the material tested on the universal testing machine is greater than 720MPa, The fracture toughness of the material measured by the unilateral notched beam method is greater than 7.8MPa·m ^1/2 .

Claims (5)

1. original position (TiB ₂+ SiC)/Ti ₃SiC ₂Diphase ceramic material is characterized in that: by stratiform Ti ₃SiC ₂Matrix and column TiB ₂, two kinds of wild phases of particulate state SiC form; TiB wherein ₂Account for 13～15% of diphase ceramic material cumulative volume, SiC accounts for 5～15% of diphase ceramic material cumulative volume.

2. method for preparing diphase ceramic material as claimed in claim 1, its concrete steps are: with raw material TiH ₂Powder, Si powder, TiC powder, B ₄C powder and Al powder are 0.9～1.3 by the mole proportioning: 1: 1.4～1.6: 0.15～2.1: 0.13～0.16 weighing; Raw material is loaded on moulding in the graphite jig that the surface scribbles supercoat behind the mechanical means mixing, hot pressed sintering in being connected with the graphite resistor furnace of protective atmosphere obtains original position (TiB ₂+ SiC)/Ti ₃SiC ₂Diphase ceramic material.

3. in accordance with the method for claim 2, it is characterized in that described TiH ₂Powder and Si Powder Particle Size are 300 orders; Described B ₄C Powder Particle Size scope is 3～10 μ m; Described TiC granularity 1～1.5 μ m; Described Al Powder Particle Size is 200 orders.

4. in accordance with the method for claim 2, it is characterized in that described hot pressed sintering process is: insulation is 50～60 minutes when being warming up to 800～900 ℃ with 10～50 ℃/min temperature rise rate first; With after 1350～1500 ℃ of 10～50 ℃/min temperature rise rate intensifications, to be forced into the heat preservation pressure sintering 1.5～2 hours every 3～5 minutes supercharging 2～3MPa, wherein heat preservation pressure is 22～25MPa again.

5. in accordance with the method for claim 2, it is characterized in that protective atmosphere is rare gas element.

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