Particulate composites pdf

The effect of the grain size can be explained by the separation of stress fields due to a greater distance between the particles and therefore a greater amount of crack bowing prior to breakaway. It is also necessary to take into account the fact i to that the crack front can interact only with particles that are larger than the grains of the matrix.

IZ the addition of the dispersed phase, can also strongly A slight increase of hardness was also fotind for some Si3N4-TiN composites [33]. It should be noted 7. Owing to this fact, and b Si3N4 TiN [] composites. In the case shown in Fig.

TiN ranging from 0. The only exception to the rule was the system Fig. In this case, most in- ceramics. Another strategy of interest for obtaining a high fracture toughness is based on using mixed 5. It enables different mech- A major focus of particulate composite research has anisms of increasing fracture toughness and work of been in the area of tribological applications [63, 82].

A Kic value of 9. Addi- 0. The highest wear resistance of the composites was observed at the highest sliding velo- 5. Hardness cities [85]. Silicon nitride is a very hard material Table I. There- TiC- or TiN-containing H P S N has a very good fore, hardness generally decreases with an increase in abrasive wear resistance pin-on-ring test on SiC the content of the dispersoid, that is softer than the paper [86].

TiN Fig. The wear in- pendence of the abrasive wear on the fracture tough- creases with increase of the diamond grain size and ness was not clearly pronounced. For ceramics with the same Fig. The increase in the wear resistance of TiN- TiN distribution, a correlation between the strength, containing ceramics was ascribed [83, 89] to the hardness and wear resistance was found [88]. A de- formation of TiO2 films on the sliding surface. A lower wear resistance at high concentrations of TiN was caused by a decrease of mechanical properties.

A drastic Figure 13 Abrasive wear versus TiN content for composites with fine and coarse TiN tested at different loads [88]. The room-temperature bending strength is greatly in- 0. Fracto- 0. The non-uni- E -I formity of the TiN particle-size distribution which can 0.

Therefore, ball- composite at sliding against steel 45 0. This can strength of composites hot-pressed in a CO-CO2, and b inert be a result of the change of the flaw population con- atmosphere. Tests in vacuum. The analysis of strength-temperature dependencies Fig. At higher temperatures, the typical strength degradation for silicon nitride ceramics 0 I I I I [31, 94, 95] due to softening of the intergranular phase 0 20 40 60 80 occurs.

Time h Fig. This is connected first of all with changes in the microstructure and composition of the intergranular phase. As can be seen from the semilogarith- mic plot, a close to exponential dependence of the 5. Creep creep rate on the TiN content is observed. A stronger change is mani- [92, 97, 98].

No information on the tensile creep tests fested at higher TiN contents. Probably, the formation is available. Fine-grained macroscopic deformation and shorter rupture times of matrix microstructure in the TiN-rich ceramics can the samples.

Higher creep rates were measured also for also be responsible for the increase of the creep rate. The quasi-stationary creep rates of the creep rate is dependent upon the temperature. On the basis of T E M investigations, it was shown that the steady-state creep rate of the composite can be regarded to be controlled by two creep compo- nents, being related to the viscous creep or cavita- tional accommodation of the matrix, and to the plastic deformation of the TiN [98] or TiC [99] skeleton.

However, the deformation of TiN plays a secondary role. The increase of the creep rate with the additive content occurs first of all due to changes in the com- position of the intergranular phase. Dis- location activity in TiC grains was much higher than in TiN [99].

Oxidation It is known, that the oxidation resistance of carbides and nitrides of refractory metals is lower than that of Si3N4 []. Therefore, their addition can put limita- tions on the application of the composites at high temperatures. The mass gain of composites increases with increasing TiN content.

Furthermore, there is a marked increase of oxidative attack with increasing TiN grain size. TiC- and HfC-containing cer- a viscous silicate film Fig. In this case, the presence of operations owing to their high fracture toughness and small TiN particles is desirable, because coarse TiN impact resistivity under these conditions [63]. Under grains prevent the formation of a continuous silicate the conditions of discontinuous turning of steel depth film on the surface and decrease its protective proper- of cut 1 mm , the wear resistance of the Si3N4-TiN ties [, ].

Experimental parts of Diesel engines, compared with a TiN-free material Fig. These com- rate was observed [30, ].

Oxidation of com- posites can replace monolithic silicon nitride in most posites can cause a strength decrease at high-temper- cases, when a high level of mechanical properties and ature tests in air [94] and can be one of the reasons for good machinability are necessary, except for very a lower creep resistance of TiN-rich ceramics [92].

Ce- Additions of other compounds, e. This ceramic was easily oxidized also during friction Ceramics with high conductivity can be used for tests []. Densification of these ceramics due to some specific electrotechnical applications. Heaters, additions of sintering aids improved their oxidation collecting electrodes and collector rings from reaction- resistance. Research Laboratory [29, All these parts can be []. These data point to the presence of strong 6.

Applications grain boundaries, limited interactions and the mech- The most common application for particulate-rein- anism of dispersion toughening in the studied systems. TiN Additions of carbides, nitrides, borides and silicides of has a low coefficient of friction. Therefore, TiN addi- transition metals increase the electrical conductivity, tion leads to improved wear resistance and extended Young's modulus, specific weight and thermal expan- tool life.

The addition of TiC to silicon nitride reduces sion coefficient of the composite and decrease its its solubility in iron []. TiN and TiC were tradi- oxidation resistance, high-temperature strength and tionally used as coatings [] and components creep resistance.

Sinterability, strength, fracture of alumina-based cutting tools [63, ]. However, only 6. Becher, M. Swain and or less systematically. For other systems, only limited S.

While some of the properties of Symposium on Metallurgy and Materials Science", edited by composites, e. Young's modulus, thermal expansion J. Bentzen Rise National Laboratory, Roskilde, , and density, can be estimated with fair accuracy p. PALM, ibid. Particulate composites appear very competitive to The alteration of the MetalL [2] E7] of technology providing homogeneous mixtures and MAH, M.

The properties can be However, the improvement in fracture tough- Vol. Snyder, R. Condrate and P. At the Tressler et al. Plenum Press, by any method, that can be used for silicon nitride New York, p. PENI, J. Effects of the A nanocomposite ap- Acknowledgements Yaroshenko and other Poroshk. Herrmann, A Suchanek, Yoshimura, Tokyo Institute of Technology, p. Yokohama, Japan, Dr A. Terpstra and R. Hong, University of Warwick, Coventry, p. UK, and other colleagues who kindly provided re- The author gratefully ac- LIU, Mater.

SHIH, J. YANG and A. PORZ, Technol. Vincenzini Elsevier, Amsterdam, p. Properties, Application" Znanie, Kiev, Forum 47 ence on Advanced Materials and Processes" Institute of Metals, London, p.

Munir Superhard PERE- Mater. LUX, J. Report Res. Engineering Materials, T. Me- 40, H. LUKAS and tall. Jpn Metal Ceram. Vincenzini Elsevier, New Hoffmann, P. Becher and G. Petzow Trans Powder Met. SATO and M. UEKI, J. ZHU, X. KING, H. XU et al. ScL 26 Jpn 97 KATO, M. A, Lab.

Wear 11 EVANS, ibid. HOLZ, R. CLAUS- Idem, J. SEN, J. Ceram Soc. GREEN, ibid. Forum 13 Brittle Materials", edited by S. Firstov IPM, Kiev, GON- WEST, ed. PARK, H. KIM, S. LEE and S. KIM, ibid. FABER, pp, Soc, 73 SAR- W. PTM'93", edited by F, Becher and G. Petzow set, pp. Trans Tech, pp. Tekhnika, HONG, R. LIN, J. YANG, S. TING, A. It provides relevant information for questions related to the selection of constituent phases, most economic fabrication routes, proper testing procedures, and product optimization.

The field is sufficiently advanced that predictive models guide many decisions. Applications are illustrated over a broad range of material and property combinations. This title includes:. The reader may have little appreciation for how particulate composites are literally everywhere. Examples include new wear resistant consumer products Apple watch , longer lasting automotive tires with reduced rolling resistance Yokohama tires , and new diamond heat sinks for computers Element Six substrates.

Particulate composites are a multi-billion dollar industry, and can be a cost-effective solution ripe for innovation and continued rapid growth. For the engineer, the wide range of particulate composite formulation and property combinations offers the ability to design for a variety of application and provides ample opportunity for innovation. Skip to main content Skip to table of contents.

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Front Matter Pages i-xvii. Pages Background Definitions. Analysis Techniques. Property Models.