P-3-01: Evaluation of the Defects in the Ceramic Layers of Composite Pipes

by Electrochemistry NDT

P-3-02: Technology to control the Thickness of the Ceramic layer in the

P-3-03: Effects of Binder Phase on the Cermet Microstructure by SHS Process

Yoo-Dong Hahn, In-Hyuck Song, Jae-Ho Jeon, Myoung-Jin Kim

Korea Institute of Machinery & Materials, Changwon, Korea
 
 

TiC based cermets are fabricated by liquid phase sintering of TiC and metal binder mixture or infiltration of metal binder into the TiC presintered skeleton. In this study, TiC based cermets with different metal binder phase such as Al, Cu, Fe, Ni, Co were prepared by SHS method and the microstructural evolution of sintered cermets were investigated.

The reacted cermets were consisted of the round shaped carbide particles and metal binder phase. The size of carbide particles varied between 1.12 to 2.39 mm depending on the metal binder. The intermediate phases comprising with Ti and metal binder were formed in the partially reacted region by arresting a propagating reaction using a wedge shaped Cu jig. Both TiC-Al and TiC-Cu cermet powders were not fully sintered at the sintering temperature of 700 and 1100^oC, respectively, due to the insufficient wettability of metal binders to TiC particles. However, nearly full density of TiC-Fe, TiC-Ni and TiC-Co cermets were obtained after sintering at 1400^oC for 1 hour in vacuum atmosphere. The carbide particles were growing during sintering and the size distribution of carbide particles became broad. Also the morphology of carbide particles was changed from round to

angular shape. In TiC-Ni system, the carbide size of SHS powder decreases with increasing Ni content due to the decreasing of combustion temperature.
 
 

References:

1. J.C. LaSalvia et al. Met.Trans A, 1995, v. 26A, p.3001.

2. M. Humenik, JR., N.M. Parikh. J. Am. Ceram. Soc., 1956, v. 39, N 2, p.60.

P-3-04: Investigation on Corrosion-Resistance Properties of Double-Layer

P-3-05: Microstructures and Mechanical Properties of Dense NiAl/ZrO₂

(3 mol% Y₂O₃) Composite Materials in the NiAl-Rich Region

(8.8 MPam1/2) are obtained for the material with 10 mol% ZrO₂ addition. They are much improved in comparison with the properties (800 MPa and 4.7 MPam1/2) of pure NiAl. High-temperature bending strength of this composite material is measured from room temperature to 1200^oC; high strengths (>810 MPa) remain up to 800^oC. A brittle-to-ductile transition occurs at ~800^oC.

P-3-06: A SHS Method for Manufacturing Dense and Functionally Gradient

TiAl_x-Al Composite Materials

Shyan-Lung Chung, Jian-Ming Sung

National Cheng Kung University Department of Chemical Engineering,Tainan,

Taiwan 70101, ROC FAX : +886-6-2344496 E-mail : slchung@mail.ncku.edu.tw
 
 

A SHS method for manufacturing dense and functionally gradient TiAlx-Ti-Al composite materials has been developed. In this method, Ti and Al powders are used as the reactants. These two powders are thoroughly mixed at appropriate ratios and then pressed into reactant compacts with desired shapes. The reactant compact and a heating element are placed in a mold which is then filled with casting sand. The combustion synthesis reaction is ignited by heating by the heating element. A mechanical pressure is applied to the mold during propagation of the combustion wave. Due to transmission of pressure by the casting sand, densification of the product is achieved, and, in the mean time, because of enhanced heat loss by densification, the combustion reaction ceases resulting in a gradient distribution of the conversion of the TiAlx compounds along the propagating direction of the combustion wave. Dense and functionally gradient TiAlx-Ti-Al composite materials are therefore produced.
 
 

P-3-07: Nitride-Oxide Ceramic Composites from SHS-Derived Powders

J. Lis, D. Kata, D. Zientara

Department of Advanced Ceramics, Faculty of Materials Science and Ceramics

University of Mining and Metallurgy - AGH Al. Mickiewicza 30, 30-059 Krakуw, Poland
 
 

The Self–Propagating High–Temperature Synthesis (SHS) can be used as a source of highly sinterable multi-phase ceramic powders. Such the powder precursors are useful for preparation of ceramic materials having attractive properties. The paper presents results of following authors’ investigations on ceramic composites prepared using SHS-derived powders. As it has been reported by the authors previously, because of specific mechanisms occurring during rapid combustion-type SHS reactions, the nitride powders prepared by the SHS method can been obtained in a specific no-equilibrium state. The SHS-ynthesis in the Si-Al-O-N system has been focused on preparation of the powders having different chemical and phase composition in metastable equilibrium. Because of these, the next high-temperature densification has a reactive sintering character, joining in a complex form the densification phenomena with chemical reactions, phase transformation phenomena, grain grown processes, etc. It makes possible to multidirectional control of materials microstructure evolution during sintering and obtain desirable properties in final materials. Several nitride-oxide composites have been investigated in the Si-Al-O-N system. Particularly two of them, the sialon-Al₂O₃ particulate nanocomposites and composites in the system of AlN-ALON-Al₂O₃ , are discussed in details. A preparation of the powders by the combustion, sintering phenomena and materials evaluations are reported with perspectives of application of such materials as a structure ceramics.

P-3-08: Fabrication and Characterization of Mo/MoSi₂ FGM by SHS

Because MoSi₂ has is resistant to oxidation in hot air above 2000K, it is hoped that it can be used as the oxidation-resistant material for refractory metals at high temperatures. However, if this material were used as the coating layer for Mo, thermal stress, thermal deformation, or cracks would occur during cooling or heating, because the coefficients of thermal expansion are different between MoSi₂ and the Mo.

In order to prevent cracks, thermal deformation, thermal stress, and so on, we attempted to fabricate and test some prototypes, which consist of Mo as the substrate metal and MoSi₂ as the oxidation-resistant layer. The prototypes have the structure of a Functionally Graded Material (FGM) similar to some composite material layers with a gradient in the compositional ratio of Mo-MoSi₂. In this paper, the protection layer, which consists of multiple layers with gradient compositional rate, was prepared and tested. A Mo/MoSi₂ Functionally Graded Material with 20 mm diameter and 5.5 mm thickness were fabricated at 50 MPa and heated to 1523K by Hot Pressing to induce a self-propagation reaction of Mo-Si₂. As a result, samples that have good relaxation of thermal stress can be obtained by this method.

P-3-09: The Microstructure of The Reaction Synthesis Ti/TiC_p Composites

P.O.Box 428, Harbin Institute of Technology Harbin, 150001 P.R.China
 
 

Titanium-based alloys have received increasing attention due to their high strength-to-weight ratio and high-temperature properties. However, to extend the usefulness of these materials, composites with high strength and lightweight reinforcements have been extensively studied. Most of these investigations concentrated on consolidating the matrix material and the reinforcement together via various techniques, the most common of which are solid-state sintering, liquid infiltration and plasma spraying. In this paper, reaction synthesis has been used to prepare titanium matrix composites reinforced by titanium carbide particles.

The processing procedure has been described in detail. During the processing, titanium powder, aluminum powder and carbon powder were mixed according to a definite chemical ratio and pressed into preform with 50~60% theoretical density, and then the preforms were heated to prepare Al/TiC master alloy. The master alloy and sponge titanium were melted by non-consumable vacuum arc melting furnace

The phases constitute has been studied by the use of X-ray diffractometry (XRD). It has been shown that there exists titanium and titanium carbide (TiC), displaying that only titanium carbide has been synthesized after this processing. The microstructures of the composites have been observed by scanning electron microscope (SEM) and transmission electron microscope (TEM). The results have shown that the TiC particles are submicron size(0.1-0.8m m), and have granular or partly spherical shape and smooth surface, and that the distribution of the TiC particles is homogeneous. The TEM results show that no reaction product has been found at the interface between the titanium matrix and TiC particles, indicting the cohesion strength between the matrix and reinforcement is stronger.
 
 
 
 

P-3-10: Some Properties of the Multicomponent thin Films Coatings produced

by D.C. Reactive Bias Magnetron Sputtering using SHS-Targets

P-3-11: Properties of Substoichiometric Titanium Carbides

A.V. Manukhin, P.V. Dvoretsky

Moscow State Steel and Alloys Institute, Leninski Prospect 4, Moscow 117936 Russia

Phone: (095) 236-7085, Fax: (095) 236-2105
 
 

The powders titanium and lamp's soot was chose for preparation of substoichiometric carbides. The different compositions of mixes was prepared. Substoichiometric carbides was obtained self-propagating high-temperature synthesis. The different properties was investigated. The dependencies of "composition-property" was presented of the graphic. The investigations was demonstrated that properties change of the nonlinear and nonmonotonous from composition of carbon. It is connected with well regulated nonmetallic atoms evidently.
 
 

P-3-12: Study on Structure and Property of Ti(Cr)B₂ Solid Solution

Synthesised by Shs

H. Wang, Z.Y. Fu, W.M. Wang, R.Z. Yuan

P-3-13: Study of the Strength-Structural Characteristics and “Preferred Size”

Weibull distribution was used for statistical treatment of the measurement results: F(P)=1-EXP[-(P/K) ^m],where F(P) is the probability of particle destruction under load < or =P; m and k are distribution parameters which can be defined

for each fraction by respective statistical processing of the experimental data.

The value of grain-destroying loading at a distraction probability of 0.63 is taken for that of grain strength ,i.e. the value of parameter k.

Weibull coefficient m can be considered as a particular structure-sensitive characteristic which determins the operation properties of certain material fraction . In addition , statistical analysis allowed isolation of stractions composed of one qualitative group and deseribed by stable Weibull curves.

Comparative analysis of the statistical date and the results of the size distribution of products of material crushing showed that the structurally uniform fractions were those of preferred size for material under study.

The proposed complex approach allows description of specific modes for behavior various fractions and the range of preferred sizes of the material under study, which provides the possibility for differential approach to evaluation of the operatial potential of material.

P-3-14: Relationship between Gibbs Energy and Adiabatic Temperature

The linear relationship between and T_ad of borides, carbides, nitrides and silicides synthesised by combustion is well known. Empirically it was established that the reaction will not be self-sustaining when Ј 2000 K, that corresponds to T_ad Ј 1800 K.

In this work a correlation between the Gibbs energy of reaction at adiabatic temperature and T_ad is proposed. The values were obtained from: . Linear relationships were found among the plots of and against T_ad for transition metals carbides and silicides characterised by the same stoichiometry. The slope of the straight line depends on the products stoichiometry. From these diagrams it can be argued an upper limit of D G° when T_ad = 1800 K for reactions characterised by different stoichiometry.

In the case of materials synthesised by a solid-gas reaction, such as nitrides, values calculated are strongly positive. Since several nitrides were obtained by combustion, it can be argued that in this case a great error is made considering both reactants at T_ad. Nevertheless the nitrides Gibbs energy of reaction at adiabatic temperature could be extrapolated by the above cited vs T_ad diagrams and applied to calculate the right nitrogen pressure need for reaction: .
 
 
 
 

P-3-15: Influence of Orientation Elastic and Strength of Properties on

Destruction Orthotropic Materials at Impact

A.V. Radchenko, S.V. Kobenko

Tomsk Branch of the Institute of Structural Macrokinetics and Materials Science

Russian Academy of Sciences,Tomsk, 634021, pr. Academicheskii, 10/3, Russia.

E-mail: maks@fisman.tomsk.su
 
 

Modern methods of material production (including SHS-method) allow to obtain materials with present properties. It is especially actual, when it is necessary to make good use of such materials in various technological processes, in which external effects on to the construction parts are known. As a rule, to provide profitable and energy-saving mode of operation of constructions it is necessary to use the materials with directivity of physical and mechanical properties i.e. anisotropy.

In the work, on the base of the investigation, being conducted earlier [1-3] the influence of orientation of strength and elastic properties on to destruction strength of orthotropic material under impact loading was investigated.
 
 

References:

1. A. V. Radchenko and N. K. Galchenko, The destruction of isotropic and anisotropic steels under dynamic loads. Fiziko-himicheskaya mehanika materialov, 1992,v. 28, N 3, p. 80-83.

2. A. V. Radchenko, I. N. Marzenyuk and S. V. Kobenko, Investigation of Properties of Anisotropic SHS Materials.4th Int. Symp. on Self - propagation High -temperature Synthesis,October.6-9,Toledo, Spain (1997).

3. A. V. Radchenko, I. N. Marzenyuk and S. V. Kobenko, The influence of heterogeneous materials anisotropy properties on their behaviour under dynamic loads. V International Conference computer -Aided Design of Advanced Materials and Technologies", August 4-6, Baikal Lake, Russia (1997).
 
 

P-3-16: Efficiency of Nickel Catalysts Formed under Extremal Conditions

of SHS Wave

² Institute of Structural Macrokinetics and Materials Science RAS, E-mail: grig@ism.ac.ru
 
 

Skeletal nickel catalysts are widly used for hydrogenation of organic compounds with multiple bonds both in industry and laboratory research. The efficiency of the skeletal nickel catalysts, prepared by leaching SHS-aluminides, has been found to be well above for olefines hydrogenation than that of common NiR catalysts [1,2].

This work aimed to the elucidation of a reason of high efficiency of SHS catalysts, in comparison to the common ones, and correlation of the efficiency and conditions of preparation.

The specific surface, sorbing and catalytic properties of nickel skeletal catalysts have been found to depend on a cooling rate of nickel aluminides after synthesis. The specific surface falls from 50 to 33 m²/g with increase in cooling rate of initial alloy from 5 to 120 K/s. In this case T_max of desorption of hydrogen from surface essentially decreases. The catalyst specific activity for hexene-1 hydrogenation linearly increases with increase in cooling rate of initial alloy (from 6 to 10 ml/minЧ m²). When it is considered that the selectivity of SHS catalysts differs little from common ones, it may be deduced that the increase of cooling rate of initial alloy during SHS process causes the increase of the number of active centers on the catalyst surface.
 
 

References:

1. Merzhanov A.G., Grigoryan E.H. et al., RU Pat. no.2050192, 1995.

2. Grigoryan E.H.," SHS Catalysts and Supports", Intern. J. of SHS, 1997, V.6, No. 3, P. 307-325.
 
 

P-3-17: Kinetics and Mechanism qf Diamond-Containing Coatings Formation

by Thermoreactive Electrospark Surface Strengthening Process

Leninsky prospect, 4, Moscow 117936, Russia.

² Ryukoku University, Jokotani 1-5, Seta, Ohtsu City 520-21, Japan.

³ Tomei Diamond Co.,Ltd, Joto 4-5-1 Oyama-city, 323, Japan.
 
 

The method of Thermoreactive Electrospark Surface Strengthening (TRESS) is presented in this paper. Thus the process of coating formation becomes a less energy consuming one as compared to the basic technology of the electrospark alloying. The additional heat of the chemical reaction of the synthesis final products formation on the substrate contribute to the increase of thickness and continuity of the coating, to the diminution of the inner tension due to the smoother elements concentration gradients throuh the coating thickness. The opportunities of TRESS method are exposed with the example of the FGM wear-resistant coating formation on the base of Ti+Al+diamond, Ti+B+diamond. Optimal conditions and technological parameters for diamond containing coatings deposition are found. The influence of a number of TRESS technological parameters (impulse discharge energy, nitrogen consumption, a content of gas evolving titanium hydride addition) on the coating composition, their structure and properties are shown. The masstransfer kinetics, the coating structure and properties were studied. The composition of the coating was determined by the X-ray and SEM analysis. The wear-resistance of coatings was evaluated by the tests on the friction machine.
 
 

P-3-18: On stabilization of the refractory single crystals growth from SHS

powders and long-sized rods products at plasma-arc melting

The process of single crystal growth from SHS-rods involvs periodic drop-by-drop replenishment of the melt. At crystal growth from SHS- powders the powder portions are added cyclic into the melt. The influence of cyclic disturbances in the crystallization system on the changes in the arc energy characteristics, the melt temperature and patterns of crystallization surface movement has been considered. The rates of crystallization and the crystal grain growth at formation of the columnar structure are found to depend on the frequency and quantity of additions to the melt. The main causes of the stability loss of the melt spatial configuration have been analyzed.

A system of low-frequency modulation of the plasma arc power is employed for increasing of the crystal growth stability and affecting the heat flow to the crystal according to the special program. As-modulated plasma arc power is correlated with the melt replenishment cycles, each of them being preceded by the melt cooling due to the modulated decrease in the arc power. At modulated decrease in the arc power there occurred the ingot crystallization. The identical conditions of the layer formation in the ingot are achieved for different replenishment cycles by modulating the arc power. Some special modes of operation of modulating system have been determined. The adverse effect of the cyclic disturbances produced by the melt replenishment on the formation of the single crystal structure has been removed. The geometric shape of the ingots obtained using the modulation technique has been significantly improved.

 P-3-19: Deep Oxidation of Methane Using SHS Catalysts

A range of oxide catalysts based on Cu-Cr, Mn and Cr have been produced using SHS and their activity has been examined in the process of deep methane oxidation. The most active matarials for this process were found to be chromium and manganese-based oxides and spinels, even though their specific surface area is very low. For the manganese catalyst, additions of cerium and epoxide tar were found to enhance significantly the catalytic properties of the SHS compounds. The beneficial effect of the Ce₂O₃ additions is probably due to increasing adsorption of oxygen, whereas the activity enhancement by the addition of epoxide tar can be explained by the creation of carbides, which adsorb methane. Conversion of methane on these catalysts (Mn-based + 5% Ce₂O₃ + epoxide tar) is at least as good as commercial catalysts at all temperatures whereas in the temperature range of l820-870K the SHS catalysts are more active.

Research is continuing in the direction of identifying the most active phases under specific conditions and increasing the specific surface area of the materials.
 
 

P-3-20: Supposed Structure of Substoichiometric Carbides and Nitrides

of IVA and VA Subgroup Transition Metals

A.V. Manukhin¹, P.B. Lopatine ²

¹Moscow State Steel and Alloys Institute, Leninski Prospect 4

Moscow 117936 Russia, Phone: (095) 236-7085, Fax: (095) 236-2105

²Juridical College, Surikova 2,Tula 300039,Russia,Phone:(0872)397539, Fax:(0872)267736

The conception of structure - ranges of co-existence structuresУ - for substoichiometric carbides and nitrides of IVa and Va subgroup transition metals have been supposed at the basis of analysis of experimental and theoretical literary data.

The Me₂X-MeX (Me - Ti, Zr; X - C, N) ranges of co-existence structures for systems Ti-C, Zr-C and mononitride TiN_x submitted.

The Me_AX_B-MeX_1,00 (Me - Nb, Ta; X - C; A, B - whole numbers) ranges of co-existence structures for monocarbides NbC_x and TaC_x submitted also.

The structures of monocarbide VC_x and mononitrides ZrN_x and VN_x have been examined from the point of ranges of co-existence structures.

^{У ranges of co-existence structures -} У A.V.Manukhin, P.B.Lopatine
 
 

P-3-21: Near Net-Shaped, Alkaline-Earth-Bearing Ceramics and Composites

by the Oxidation of Metal-Infiltrated Preforms

Mg + Al₂O₃ => MgAl₂O₄
 
 

Hence, as will be shown, dense, solid AE metal/oxide bodies can be converted by oxidation into AE compounds with a retention of shape and dimensions. In a second process, molten AE metal is allowed to infiltrate and undergo a displacement reaction with a porous oxide-bearing preform. In this case, unlike other displacement reaction methods (C4, RMP, i-AAA), reactions are chosen that generate a larger volume of oxide than is consumed. Such volume-increasing reactions act to fill in the pores within the preform, so that dense ceramic/metal composites are produced with little change in the external specimen dimensions (near net-shape processing). By varying the liquid and preform composition and the preform porosity, a wide range of ceramic composites can be produced (e.g., composites with discontinuous metal particles or with co-continuous, interpenetrating metal filaments). This process has been used to fabricate dense, near net-shaped, i) lightweight, hydration-resistant, oxide-rich MgO/Mg-Al composites, and ii) co-continuous MgAl₂O₄/Fe-Ni-Al alloy composites with toughness values up to 13 MPa.m^1/2.
 
 

P-3-22: Superplasticity of Mechanically Alloyed Nanocrystalline and

Amorphous Materials

O.M. Smirnov

Laboratory of Superplastic Materials Deformation Moscow State Steel and Alloys Institute

Leninsky prospect, 4, Moscow 117936, Russia
 
 

Amorphous alloys with small volume fraction of nanocrystalline dispersed phase are known to have a very high mechanical strength and low ductility at low and high temperatures compared with those for crystalline alloys. On the other hand, some recently developed bulk amorphous alloys with large glass-forming ability have shown striking superplastic-like behavior and very high formability in supercooled liquid state, which seem to be promising for future development as a new type of superplastic intermetallic materials. One of the most powerful tools for producing bulk amorphous alloys is mechanical alloying. Other forms of severe plastic deformation can be used to yield traditional fine-structure superplastic (FSS) and high-strain-rate superplastic (HSRS) alloys. Rheological behavior of two groups of superplastic materials is analyzed on the base of mass-transfer mechanics considerations. The first group is

distinguished by ultra-fine submicro- and nano-scale grains as the basic mass-transfer units and includes FSS and HSRS alloys. Materials that exhibit superplastic and superplastic-like flow on the basis of moving atoms or their groups as mass-transfer units can be unified in the second group. Inorganic glass-forming systems (non-metallic as well as metallic) and materials that display phase-transformation superplasticity are the members of this group. An analysis of apparent shear viscosity in superplastic flow of these materials as the function of solid-phase volume fracture as well as of strain rate and deformation temperature shows the evidence of rheological similarity among the materials mentioned above. Rheological properties of all these materials vary inside the range between pure viscous and viscoplastic types. Thermodynamical analysis of viscous flow of metallic glasses show that the typical mass-transfer unit in supercooled liquid state is a group of atoms limited by two to three co-ordination spheres. High-strain-rate superplasticity and very low shear viscosity exhibited by bulk amorphous alloys are considered as promising features for development of new metal forming technologies.
 
 

P-3-23: Manufacturing and Application of Hard-Alloy Large-Scale SHS Items

At ISMAN, the equipment (based on hydraulic presses with force of 4000 and 20000kN) and production method for manufacturing large-sized hard alloy items have been designed. These method and facilities have been used for producing items to be used in industry (rolls for hot and cold metals rolling, wear-resistant rings for paint mills, press-dies, targets for magnetron sputtering, etc.). Many of these items were tested in industry and they were found to meet all the necessary requirements. For example, the wear-resistant rings have been used at a paint plant, the rolls for hot copper rolling by using the MORGAN rolling machine were found to be 2–4 times more stable than steel ones.

Recently a number of press-dies for manufacturing large-sized hard alloy items (100–320 mm in diameter) have been developed and applied in practice at ISMAN.