CN1344810A - In-situ compounding process of preparing silicon carbide particle reinforced molybdenum silicide based composite material - Google Patents

Abstract

By means of controlling the compounding technological parameters of in-situ, eliminating the low temperature solid-solid reaction among Mo, Si and C element powder and utilizing the their soild-liquid reaction, composite MoSi2-SiC powder is in-situ compounded and densified through secondary heating so as to prepare fine dispersed SiC particle reinforced MoSi2 composite two-phase material with clean interface and no SiO2 glass phase and other transition phases. The composite material has high temperature oxidation resistance of MoSi2, improved low temperature and high temperature mechanical performance as well as the preparation process is easy to control and simple in equipment.

Description

A kind of in-situ compounding process for preparing silicon carbide particle reinforced molybdenum silicide based composite material

Technical field:

The invention belongs to the alloy material preparation field, particularly the preparation of intermetallic compound silicon molybdenum thing based composites.

Background technology:

MoSi ₂Has fusing point, lower density (6.24g/cm up to 2030～2050 ℃ ³), good resistance of oxidation with the thermal conductivity of metal same level and low thermal expansivity, can satisfy the basic demand as high-temperature structural material.The more important thing is that though this compound shows the fragility same with pottery in room temperature, it has the tough-brittle transition behavior, more than ductile-brittle transition temperature, the motion of dislocation and significant reaction activate, and intensity is controlled by plastic deformation.Therefore, under use temperature, will have higher reliability than structural ceramics.In addition, MoSi ₂Can or form matrix material with considerable element and compounds aurification, make it keep Thermodynamically stable.Like this, just multiple means and possibility are provided for improving performance.Therefore, MoSi ₂Be considered to the high-temperature structural material that has competitive power that occurs after the structural ceramics of Ni, Ti superalloy and use temperature＞1000 of 800～1000 ℃ of use temperatures ℃, getting a good chance of as use temperature is that 1000～1600 ℃ various high-temperature structural materials are used.

But low toughness under the room temperature, high temperature down with the deficiency of ceramic phase specific tenacity, particularly lower creep resistance is hanged down and has been limited MoSi ₂Application as high-temperature structural material.Therefore keeping MoSi ₂Under the prerequisite that oxidation-resistance does not reduce substantially, how to improve MoSi ₂Low-temperature flexibility and hot strength are exploitation MoSi ₂The key of high-temperature structural material.Existing work shows that soft or hard second phase can be improved its room temperature and mechanical behavior under high temperature simultaneously.In numerous enhancing bodies, SiC has good chemical stability, high intensity and Young's modulus, and low thermal expansivity, high fusing point is with MoSi ₂Good chemical compatibility and physical compatibility are arranged, same MoSi ₂-sample has good oxidation-resistance, is considered to strengthen MoSi ₂One of the most effective enhancing body.

At present, preparation MoSi ₂The original position recombining process of-SiC matrix material has: replacement(metathesis)reaction, reactive plasma deposition, mechanical alloying, XD ^TM, burning synthetic induction heating thermal explosion pattern, the auxiliary SHS that reaches of electric field add quasi-hot isostatic pressing simultaneously, and the reaction of direct hot pressing element simple substance mixture and element powders is synthetic synchronously etc.Wherein, replacement(metathesis)reaction (Henager C H Jr, et al.Mater.Sci.Eng.A, 1992, A155:109～114), reactive plasma deposition (Lawrynowicz D E, et al.High-Temperature Ordered IntermetallicsAlloy VI, P923.), mechanical alloying (Jayashankar S, et al.J.Mater.Res., 1428～1441.), XD 1993,8 (6): ^TMIn the sample of (Aikin R M Jr, et al.Mater.Sci.Eng.A, 1992, A155:121～133.) these prepared except MoSi ₂Outside the SiC two-phase, all there is other transition phases (Mo for example to some extent ₅Si ₃, Mo _{≤ 5}Si ₃C _{≤ 1}Deng) and glassy phase, and former three second phase volume fraction can not arbitrarily be regulated and control XD ^TMProcess using hot pressing and hot isostatic pressing two procedures are compact formed, and preparation section is many, control is quite complicated; Burning synthetic sample is because the too fast structural constituent of reaction is difficult to control, there is macrosegregation, tissue odds is even, sometimes also reaction is incomplete, the hot-forming back second phase SiC particle is obviously assembled, size big (up to 20 μ m), and equipment complexity (Chrysanthou A, et al.J.Mater.Sci., 1996,31 (16): 4221～4226; Bartlett A H et al.J.Mater.Sci., 1998,33 (6): 1653～1660.); Direct hot pressing element simple substance mixture (Alman D E, et al.Scrip.Metall.Mater., 1994,273～278.) and synthetic synchronously (the Alman D E of the reaction of element powders 31 (3):, et al.Scrip.Metall.Mater., 1993,28 (12): 1525～1530) also have transition phase in Zhi Bei the sample, and the former C fiber does not change into SiC fully, reaction not exclusively, the synthetic synchronously compact formed matrix material of hot isostatic pressing technique that adopts of the reaction of element powders, the equipment complexity, the cost height, the second phase SiC particle size is big, assemble serious, skewness.The MoSi of above-mentioned many prepared ₂The mechanical property that the appearance meeting of glassy phase significantly reduces material in the-SiC matrix material is mechanical behavior under high temperature especially, and the second phase SiC particle size is big, assemble remarkable improvement serious, that skewness also is unfavorable for composite materials property, and Mo ₅Si ₃Can reduce the high temperature oxidation resistance of matrix material etc. the existence of transition phase.

The objective of the invention is to prepare silicon carbide particle reinforced molybdenum silicide based composite material, do not reducing MoSi by control original position recombining process parameter ₂Under the prerequisite of high temperature oxidation resistance, improve MoSi to greatest extent ₂The low temperature of-SiC matrix material and mechanical behavior under high temperature, and technology is easy to control, equipment is simple.

Summary of the invention:

The present invention is by control original position recombining process parameter, solid eliminate low temperature between Mo, Si and the C element powder solid-reaction, and utilize the solid-liquid reaction original position between them to synthesize MoSi ₂-SiC composite powder, and with fine and close this MoSi of secondary hot pressing ₂-SiC composite powder prepares interface cleaning, no SiO ₂Glassy phase and Mo ₅Si ₃, Mo _{≤ 5}Si ₃C _{≤ 1}Wait other transition phases, small and dispersed SiC particle to strengthen MoSi ₂Two-phase composite material.The concrete related MoSi of the present invention ₂The chemical constitution of-SiC matrix material by volume per-cent is MoSi ₂-0%SiC～MoSi ₂-100%SiC, the content of element powders calculates by the stoichiometric ratio of corresponding composition proportioning matrix material.The concrete preparation process of matrix material is as follows: be pressed into the green compact sample after element powders is weighed up and mixes by proportioning, green density is 60～75% of a mixed powder theoretical density.The green compact sample carries out reaction in and synthesizes after 400～600 ℃ of vacuum outgass in the mobile pure argon, stove is chilled to room temperature then.Reaction in synthetic technology is: 1410～1470 ℃ of temperature, 120 ℃/min of temperature rise rate, soaking time 0.5～1h.After material fragmentation with reaction in after synthetic becomes 180 μ m～450 μ m powder, carry out hot-forming, 1700～1750 ℃ of temperature, soaking time 1～2h, 30～the 40MPa that exerts pressure is cooled to 400～500 ℃ with the speed of 10～20 ℃/min, naturally cools to room temperature at last.Decompression gradually behind pressurize to 1200 in the process of cooling after hot pressing～1300 ℃.All the time feeding mobile Ar gas in the hot pressing protects.

The invention has the advantages that by control original position recombining process parameter, solid can eliminate low temperature between Mo, Si and the C element powder solid-reaction, effectively utilize the solid-liquid reaction original position between them to synthesize MoSi ₂～SiC composite powder by secondary hot pressing, makes the matrix material of the densification of acquisition can guarantee to have only MoSi again ₂With the SiC two-phase, interface cleaning, no SiO ₂Glassy phase and Mo ₅Si ₃, Mo _{≤ 5}Si ₃C _{≤ 1}Wait other transition phases, the second phase SiC particle small and dispersed to be distributed in MoSi ₂On the matrix, therefore, this matrix material can be guaranteed do not reducing MoSi ₂In the time of high temperature oxidation resistance, can improve the low temperature and the mechanical behavior under high temperature of matrix material to greatest extent.Because the present invention only need control original position recombining process parameter, need not hot isostatic apparatus, so technology easy, be easy to control, equipment is simple.

Description of drawings:

Fig. 1 is MoSi ₂The XRD spectral line of-SiC matrix material.

Fig. 2 is MoSiC30 matrix material MoSi ₂HREM picture with SiC two-phase phase boundary.

Fig. 3 is the metallographic structure of MoSiC30 matrix material.

Fig. 4 is MoSi ₂-SiC matrix material room temperature fracture toughness property is with the variation of SiC volume fraction.

Fig. 5 is single MoSi ₂(a) and MoSiC30 (b) compression true stress-strain curve.

Synthetic and the commercial powder MoSi that mixes of hot pressing of original position when Fig. 6 is stress 80MPa ₂The creep curve of-30%SiC relatively.

Embodiment

Embodiment: test MoSi ₂The chemical constitution of-SiC matrix material by volume per-cent is MoSi ₂-30%SIC writes a Chinese character in simplified form into MoSiC30, and the content of element powders is calculated as by the stoichiometric ratio of forming MoSiC30: Mo: Si: C=51.71: 42.90: 5.39wt%.Used starting material are Mo powder, Si powder and Graphite Powder 99, and mean particle size and purity are Mo:8 μ m, 99.0%; Si:7 μ m, 99.0%; C:22, μ m, 99.9%.After element powders weighed up by proportioning, add the different ZrO of an amount of diameter ₂Ball and dehydrated alcohol, wet mixing 10h on the roller ball mill.The powder that mixes is pressed into φ 30 * 15mm circle base sample, and pressed density is 70% of a mixed powder theoretical density.Circle base sample carries out original position in the pure argon 99.91% after 500 ℃ of vacuum outgass synthetic, and stove is chilled to room temperature then.Concrete technology is: 1450 ℃ of temperature, 120 ℃/min of temperature rise rate, soaking time 1h.After material fragmentation with reaction in after synthetic becomes 180 μ m powder, carry out hot-formingly, pressed compact is of a size of about φ 50mm * 8mm, 1740 ℃ of temperature, soaking time 2h, 40MPa exerts pressure, speed with 10 ℃/min is cooled to 500 ℃, naturally cools to room temperature at last.Decompression gradually after the pressurize to 1300 ℃ in the process of cooling after hot pressing.All the time feeding mobile Ar gas in the hot pressing protects.

The MoSiC30 matrix material that obtains through above-mentioned technology only contains MoSi ₂With the SiC two-phase, do not contain Mo ₅Si ₃, Mo _{≤ 5}Si ₃C _{≤ 1}Wait other transition phases, nor have SiO ₂Glassy phase, interface cleanness are seen Fig. 1, Fig. 2.The SiC particle size is 3～5 μ m, and evenly tiny, disperse is distributed in MoSi ₂On the matrix, see Fig. 3.The porosity of this matrix material is (0.044 ± 0.014) %, can think to reach complete densification.The room temperature fracture toughness property of this material is than single MoSi ₂Have clear improvement, see Fig. 4.1000 ℃, 1200 ℃, 1400 ℃ high temperature compressed flow curve is apparently higher than single MoSi ₂, its high-temperature stream varying stress, yield strength significantly improve, and see Fig. 5.Its high temperature creep drag is much higher than the MoSi of the prior powder metallurgy prepared that adopts the commercial mixed powder of hot pressing ₂-30%SiC matrix material is seen Fig. 6.

Claims (2)

1, a kind of in-situ compounding process for preparing silicon carbide particle reinforced molybdenum silicide based composite material, MoSi ₂The chemical constitution of-SiC matrix material by volume per-cent is MoSi ₂-0%SiC～MoSi ₂-100%SiC, the content of element powders calculates by the stoichiometric ratio of forming this matrix material, it is characterized in that reaction in synthetic technology is: 1410～1470 ℃ of temperature, temperature rise rate 〉=120 ℃/min, soaking time 0.5～1h.After material fragmentation with reaction in after synthetic becomes-40～-80 order powder, carry out hot-forming, 1700～1750 ℃ of temperature, soaking time 1～2h, 30～the 40MPa that exerts pressure is cooled to 400～500 ℃ with the speed of 10～20 ℃/min, naturally cools to room temperature at last.Decompression gradually after 1200～1300 ℃ in the process of cooling after hot pressing.

2, in-situ compounding process as claimed in claim 1, the preparation that it is characterized in that matrix material are to be pressed into the green compact sample after element powders is weighed up and mixes by proportioning, and green density is 60～75% of a mixed powder theoretical density.The green compact sample carries out reaction in and synthesizes after 400～600 ℃ of vacuum outgass in the mobile pure argon.

Images