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High-temperature heat-shielding, ceramic and ceramic-metal composite materials for new-generation aviation equipment

https://doi.org/10.38013/2542-0542-2020-2-83-92

Abstract

This paper describes achievements of the All-Russian Scientific Research Institute of Aviation Materials in the field of creating high-temperature heat-shielding, ceramic and metal-ceramic composite materials. The advantages and prospects of applying the developed materials in the manufacturing of structural elements of aircraft and friction joints are discussed. The synthesis features and basic properties of metal-ceramic composite materials based on light alloys, refractory metal matrices, ceramic composite materials for use in heavily loaded structural elements of modern aircraft are presented. The main achievements in the field of heat-shielding materials based on refractory oxide fibres are presented, along with their properties and application in new-generation aircrafts.

For citation:


Balinova Yu.A., Graschenkov D.V., Shavnev A.A., Babashov V.G., Chaynikova A.S., Kurbatkina E.I., Bolshakov A.N. High-temperature heat-shielding, ceramic and ceramic-metal composite materials for new-generation aviation equipment. Journal of «Almaz – Antey» Air and Space Defence Corporation. 2020;(2):83-92. https://doi.org/10.38013/2542-0542-2020-2-83-92

Introduction

One of the key activities of FSUE VIAM is the development of high-temperature heat-shielding, ceramic and metal-ceramic composite materials for prospective items of aviation and rocket equipment [1][2]. The most remarkable example is the design of reusable external heat-shielding tiles for Buran orbital spaceship (USSR) [2]. The heat-shielding, ceramic and metal-ceramic composite materials considered in this overview allow to increase the operating temperatures of aircraft structural elements with simultaneous increase of service load [3].

Metal-ceramic composite materials (MCM) offer important advantages, such as high rigidity, strength, crack resistance, wear resistance, high operating temperatures. Of these, the first and foremost used materials are composite materials based on aluminium and titanium matrices, particle- and fiber-reinforced [3]. Such materials are widely introduced in the foreign advanced equipment samples. Thus, fibrous fiber-reinforced MCM based on titanium and intermetallic titanium alloys are used in heavy loaded structural elements: rods, levers, high pressure vessels, edges, high and low pressure compressor blades. Aluminium-based low-filled dispersion-hardened MCM are used in primary structure elements, fuel tank shells, hydraulic systems. Highly filled MCM with aluminium matrix are used in power electronics (IGBT-modules, electric drive control systems, switched mode power supply sources, etc.).

Mechanically stressed heat-loaded structures require materials based on thermal resistance matrices. The most prospective materials of this class include molybdenum-, niobium-and nickel-based composites [4][5][6][7][8], their performance characteristics being improved by using alloying technologies and dispersion and ceramic fiber hardening. Articles manufactured of metal composite materials based on Мо, Nb, Ni may have operating temperature from 1200 to 1600 °С.

MCM based on highly filled nickel alloys are prospective materials for tribotechnical application in heavily loaded friction assemblies operating at high temperatures with limited lubrication [10]. Carbides, nitrides, carbonitrides, borides, silicides, oxides, intermetallic compounds and more complex ceramic-like compounds, as well as combinations of the same are used as a ceramic component. Additionally, the composition may include substances of a solid lubricant class (graphite, molybdenum disulfide, hexagonal boron nitride, etc.) and low-melting metals forming hydrodynamic lubrication in thin layers. In sliding friction pairs made of highly filled MCM, low values of friction coefficient and low wear rate can be achieved.

In order to manufacture most heavily loaded body elements, parts of engine hot section and elements of radiotechnical structures with operating temperatures exceeding 1500 °C for new-generation aviation equipment, it is necessary to use low-weight ceramic and glass-ceramic composite structural materials having high strength, hardness, crack resistance, corrosion and erosion resistance together with long life cycle under the conditions of high temperature oxidation [11][12].

Even higher operating temperatures are ensured by heat-shielding materials designed to protect structural elements against external and internal thermal exposure during aircraft operation, at the same time providing additional protection against oxidation factors.

VIAM has several decades of history of the spacecraft heat shielding development. VIAM has developed the screen vacuum thermal insulation for the descent module of Vostok spacecraft and all subsequent spacecraft, including Buran orbital spaceship [1]. To some extent, heat shielding is a critical element for the serviceability of spacecraft, including recoverable ones, since it is the heat shielding which ensures the integrity and normal functioning of both individual assemblies and structures and the craft itself.

Currently, FSUE VIAM develops materials for aviation and rocket-and-space equipment based on a new approach with consideration of the classic models.

Study subjects and methods

Metal-ceramic composite materials were produced using both powder metallurgy methods and liquid-phase technologies (soaking, infiltration) combined with spark plasma sintering method. Ceramic composite materials were produced by hot pressing, spark plasma sintering and sol-gel methods. Heat-shielding materials were produced using sol-gel technology.

Mechanical characteristics were studied using tensile testing machines Instron 5965, Instron 5882, Zwik Z010 in accordance with standard procedures and GOST.

Thermal linear expansion coefficient was studied using high temperature dilatometer DL-1500 H/HR in the temperature range from 20 to 1400 °C, heat-conductivity coefficient was determined following dynamic method of laser flash using solids thermophysical properties measurement device LFA 427 in the temperature range from 20 to 1900 °C with subsequent approximation to higher temperatures.

To study the materials microstructure, raster electron microscopy method was applied with microscopes S-405, Verios 460 XHR, Zeiss EVO MA 10.

1. Digital modelling in developing metal and ceramic composite materials and heat shielding

Material multi-level modelling at nano-, micro-, meso- and macrolevels (see the diagram in Figure 1) ensures implementation of “material - technology - design” integrity principle.

Fig. 1. Material multi-level modelling diagram

Fundamental studies begin with atomic and molecular design and quantum-mechanical calculations. Then, a successive transition to the nanolevel of studying molecular interactions is made. Microlevel studies are based on the phase stability parameters calculation and scientific search of new synthesis methods for complex chemical compounds. Mesolevel marks the beginning of applied studies with a transition to marcolevel of materials and new-generation technologies.

Currently, VIAM actively uses digital technologies for modelling inhomogeneous metal-ceramic media. It has developed 9 multifactor models for 6 classes of reinforced, dispersion-strengthened and fibrous CM and heat shielding.

2. Metal composite materials based on light alloys

FSUE VIAM develops and manufactures aluminium- and titanium-based metal-ceramic composite materials in the form of dispersion-strengthened low- and highly filled CM.

Within the framework of joint work with the Russian Science Foundation, studies were carried out to investigate the impact of the composition of aluminium alloys, series 6ХХХ (6061, 6063, 6092), 2ХХХ (2024, 2009), 7ХХХ (7075, 7050), and the filler percentage on physical and mechanical properties of composite materials. It was demonstrated that aluminium matrix composite materials with aluminium alloys of series 7ХХХ (r ~ 3.0 g/cm3, s20B ~ 700 MPa, Е20 ~ 115 GPa, s20сж ~ 705 MPa) have the maximum mechanical properties.

The studies were carried out and a manufacturing technology was developed for highly filled MCM of Al-SiC system and articles made of the same. The composite material has the following properties: ρ = 2.9-3.0 g/cm3, α = 6.9÷7.2 K-1  (within the temperature range of 20-100 °С), X = 130-150 W/mK (within the range from 20 to 100 °С). The unit of pressure-assisted and vacuum-driven impregnation of porous ceramic skeletons with matrix alloy was developed, production of heat-transmitting base members made of Al-SiC CM was established at the premises of PJSC Elektrovypryamitel with the capacity of up to 10,000 pcs/year.

Complex studies on the development of fibrous composite materials based on titanium matrices were carried out for heavy loaded aircraft structures. The relationships between mechanical characteristics of composite materials, titanium-based matrix composition and filler volume ratio were established.

This resulted in the development of an in-termetallic titanium-based material outperforming its foreign analogues by physical and mechanical indicators: ρ ~ 4.5 g/cm3, σ20В ~ 1680 MPa, Е20 ~ 200 GPa, σ 20сж ~ 2300 MPa.

3. Metal high-temperature composite materials

Development of articles made of high-temperature metal composite materials based on Мо, Nb, Ni, Fe dispersion-hardened matrices is actively studied world-wide. Such interest is due to extremely high structural stability, high strength profile, chemical inertness and corrosion resistance of dispersion-hardened metal composite materials based on refractory metals.

FSUE VIAM has developed high-temper-ature metal composite materials based on iron, nickel, molybdenum, niobium matrices using the technologies of MCM dispersion and ceramic fiber hardening. Relations between the composition and content of strengthening phase in MCM based on Мо, Nb, Ni, Fe matrices and physical and mechanical and thermal properties of the end material were established. Reinforcement of refractory matrices with ceramic fiber allowed to develop a complex of composite materials characterised by 20-30 % lower specific weight, 10-20 % higher operating temperature, 1.5-2.0 times higher mechanical characteristics and greater resistance to heat ageing compared to matrix material.

Composite materials based on refractory matrices are intended for use in heat-loaded structural elements operating under high mechanical stress. Application of the developed metal-ceramic composite materials will ensure serviceability of structural elements of prospective AC at temperatures >1400 °С.

Highly filled MCM of tribotechnical application were developed, and by their tribotech-nical properties these materials are as good as ceramic ones and have certain advantages over the latter. Due to metallic bond, metal-ceramic materials are resistant to vibration and impacts. By selecting friction counterfaces made of metal-ceramic materials with different compositions, low friction coefficient and high wear resistance can be achieved.

4. Ceramic/glass-ceramic composite materials and antioxidizing coatings

FSUE VIAM actively works on the development of high-temperature ceramic and glass-ceramic composite materials (CCM and GCCM, respectively), as well as of the technologies for aircraft structural elements manufacture out of these materials with the use of unique technologies.

For consolidation of powders during obtaining a wide range of materials (high-temperature, composite nanostructural, gradient and many other), FSUE VIAM actively uses innovative (combined) hybrid-heated FAST/ SPS technology, including spark plasma sintering and induction heating. Application of this technology allowed to develop a range of ceramic composite materials based on refractory compounds of rare and rare-earth metals with a uniform finely crystalline structure, bending strength of up to 450 MPa and operating temperatures >1700 °C. Microstructure of CCM, obtained using hybrid FAST/SPS method, is shown in Figure 2.

Fig. 2. Microstructure of CCM obtained using FAST/SPS method

FSUE VIAM carries out work aimed at developing sol-gel technologies for airborne ceramic and glass-ceramic composite materials manufacture. Systematic studies allowed to increase operating temperatures of glass-ceramic composite materials from 500÷700 to 1500 °С. Composite materials of radiotechnical applications were developed based on alkali-free aluminosilicate ceramics, which are characterised by a unique combination of dielectric and thermal properties. Increased crack and thermal resistance together with reduced fusion temperature and unchanged radiotechnical characteristics of glass-ceramic composite materials will guarantee an advantage over the best domestic and foreign analogues, increase marketability of domestic products in the foreign and Russian markets.

Studies were carried out and a manufacturing technology was developed for ceramic emitters based on lanthanum hexabo-ride, intended for zero-defect electron-beam welding of oversize complicated parts made of heat-resistant, high tensile, corrosion-resistant steels, titanium and other alloys. Due to achieving high density and smoothness of surface, as well as ensuring uniform microstructure, emitters provide stable emission current at a level of >500 mA. At present, FSUE VIAM has mastered pilot industrial production of ceramic emitters with the capacity of 1500^2000 pcs/year.

Using hot pressing method, FSUE VIAM has developed a technology for obtaining ceramic composite material of grade VMK-17 with increased thermal resistance up to 1700 °C and inactivity in relation to metal melts impact, and a technology for nozzles manufacture of this material, used during spraying of airborne alloys for additive technologies. Introduction of the developed technologies into FSUE VIAM own production allowed to expand the assortment of obtained powders due to the possibility of their spraying temperature increase. The developed technologies contribute to solving the problem of import substitution and development of additive technologies in the aviation industry of Russia.

5. High-temperature heat-insulating, heat-shielding and sealing materials

For over 30 years, VIAM has been working on the development of unique heat-shielding and heat-insulating materials.

To date, it has developed new types of high-temperature fibers of refractory silicon, aluminium, zirconium oxides with the operating temperatures of 1700 °C and higher. Heat-shielding, heat-insulating and sealing materials were developed based on them.

The studies were carried out on the synthesis of sol-gel precursors of refractory oxides fibers with the use of commercially-avail-able domestic raw material. Engineering and manufacturing batch production sections were organized to provide the domestic machine-building industry with high-temperature insulation and heat-shielding materials.

Fundamental and applied studies aimed at revealing the relationships between the structure, physical, mechanical and thermophysical properties of heat-shielding materials are the basis for applied studies and application of heat-shielding materials. Scientific studies resulted in the development of materials having high flexibility, elasticity and producibility, ensuring their convenient application during heat insulation of complex-shaped surfaces against long-term impact of high-capacity heat flow. Specific weight of materials may vary from 30 to 300 kg/m3, the operating temperatures of materials based on basalt fibers and aluminium oxides vary from 1200 to 1700 °С, the materials based on more refractory oxides have operating temperatures exceeding 1700 °C. Bend radius before fracture varies from 30 to 600 mm depending on the material of fibers, density and material thickness.

Figure 3 shows temperature dependencies of heat-conductivity coefficients of flexible materials samples with different density, manufactured based on aluminium oxide fibers.

Rigid heat-shielding materials are manufactured of high-temperature fibers in the form of blocks, they are intended for the use as heat-shielding and heat-insulating material under the conditions of direct impact of heat flow with mass transfer. Density of materials may vary from 250 to 1000 kg/m3 at porosity from 50 to 94 %. Compression strength depends on material density and varies from 0.5 to 2.5 MPa. Heat-conductivity coefficient depends on porosity to a greater extent than on material composition, and equals to 0.3-0.6 W/(mK).

Figure 4 shows typical temperature dependency of heat-conductivity coefficient for materials with porosity equal to 80-84 %. Materials based on different refractory oxides have comparable values of heat-conductivity coefficient. The basic difference between the materials is their operating temperature.

Fig. 4. Typical temperature dependency of heat-conductivity coefficients of materials based on refractory oxides with porosity of 80÷84 %

Sealing materials, cords and braids made of high-temperature fibers were developed. Heat insulating cords of grade VShT are intended for the use as thermal seals operating within the temperature range from minus 130 to plus 1200 °С, and as dynamic seals with increased abrasion resistance (Fig. 5). Sealing cords of grade VShU-1 based on most heat-resistant fibers are intended for the use as joint sealing and heat insulation in different heating plants and gas turbine engines with the operating temperature of up to 1800 °С.

Fig. 5. High-temperature sealing cords of grades VShT and VShU-1

Conclusion

An overview was given for present-day developments in the field of high-temperature heat-shielding, ceramic and ceramic-metal composite materials for new-generation aviation equipment.

The basis of contemporary approach to the development of composite materials and heat shielding for aviation engineering was disclosed; this approach is based on the multi-level modelling at nano-, micro-, meso-and macrolevels and ensures implementation of “material - technology - design” integrity principle.

The basic properties were presented for ceramic-metal composite materials based on light aluminium and titanium alloys, refractory metal dispersion-hardened matrices reinforced with continuous fibers. Developments in the field of ceramic composite materials with the use of new-generation energy-efficient technologies were presented. Main achievements in the field of heat-shielding materials based on refractory oxides fibers were analysed, along with their properties and applications.

An overview was given for high-tem-perature metal composite materials based on iron, nickel, molybdenum, niobium matrices, with the operating temperature range from 1200 to 1600 °С. Options for increasing performance characteristics of high-temper-ature metal composite materials were presented, and the main advantages of proposed approaches were pointed out.

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About the Authors

Yu. A. Balinova
All-Russian Scientific Research Institute of Aviation Materials (VIAM)
Russian Federation

Balinova Yulia Aleksandrovna – Cand. Sci. (Engineering), Leading Engineer

Research interests: promising fibers of refractory oxides, heat-shielding and heat-insulating materials.



D. V. Graschenkov
All-Russian Scientific Research Institute of Aviation Materials (VIAM)
Russian Federation

Graschenkov Denis Vyacheslavovich – Cand. Sci. (Engineering), Deputy Chief Executive Officer

Research interests: ceramic and glass-ceramic materials, ceramic-metal composite materials and thermal protection.



A. A. Shavnev
All-Russian Scientific Research Institute of Aviation Materials (VIAM)
Russian Federation

Shavnev Andrey Aleksandrovich – Cand. Sci. (Engineering), Head of R&D Department

Research interests: ceramic-metal composite materials based on aluminium and titanium alloys.



V. G. Babashov
All-Russian Scientific Research Institute of Aviation Materials (VIAM)
Russian Federation

Babashov Vladimir Georgievich – Cand. Sci. (Engineering), Laboratory Head

Research interests: promising fibers of refractory oxides, heat-shielding and heat-insulating ceramic composite materials.



A. S. Chaynikova
All-Russian Scientific Research Institute of Aviation Materials (VIAM)
Russian Federation

Chaynikova Anna Sergeevna – Cand. Sci. (Engineering), Laboratory Head

Research interests: ceramic composite materials, glass ceramics, high-temperature enamels, sol-gel technology, SPS method.



E. I. Kurbatkina
All-Russian Scientific Research Institute of Aviation Materials (VIAM)
Russian Federation

Kurbatkina Elena Igorevna – Cand. Sci. (Engineering), Laboratory Head

Research interests: ceramic-metal composite materials based on light metals and their alloys.



A. N. Bolshakov
All-Russian Scientific Research Institute of Aviation Materials (VIAM)
Russian Federation

Bolshakova Alexandra Nikolaevna – Cand. Sci. (Chemistry), Laboratory Head

Research interests: ceramic and ceramic-metal composite materials based on refractory metals and their alloys.



For citation:


Balinova Yu.A., Graschenkov D.V., Shavnev A.A., Babashov V.G., Chaynikova A.S., Kurbatkina E.I., Bolshakov A.N. High-temperature heat-shielding, ceramic and ceramic-metal composite materials for new-generation aviation equipment. Journal of «Almaz – Antey» Air and Space Defence Corporation. 2020;(2):83-92. https://doi.org/10.38013/2542-0542-2020-2-83-92

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