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Mechanical Seal Selection and Application
Published in Heinz P. Bloch, Allan R. Budris, Pump User’s Handbook, 2021
Heinz P. Bloch, Allan R. Budris
Reaction bonded silicon carbide with approximately 12% free silicon provides high hardness, good thermal conductivity, resistance to heat checking, and excellent dry-running behavior. Direct sintered silicon carbide has improved chemical resistance even if exposed to liquids with a pH value above 11, but also possesses an increased coefficient of friction. Increased friction will have a significant influence on the total power consumption of a seal system (Ref. 8–9).
Ceramic Armour
Published in Paul J. Hazell, Armour, 2023
Usually, reaction-bonded silicon carbide is manufactured by infiltrating a preform of silicon carbide and carbon particles with molten or vapourized silicon (Si). The silicon and the carbon react to form silicon carbide (as above), which bonds the original silicon carbide particles together. The resulting structure will be a composite of silicon and silicon carbide. The carbon is usually completely consumed.
Mechanical Seal Face Materials
Published in Heinz K. Müller, Bernard S. Nau, Fluid Sealing Technology, 2019
Heinz K. Müller, Bernard S. Nau
Reaction-bonded silicon carbide (SiC-Si) is made from α-SiC powder and graphite, which are infiltrated with silicon liquid or vapor to form a bonded composite of α-SiC, β-SiC, and silicon. It is widely used in mechanical seals, having particularly good tribological properties including a high thermal conductivity.
Characterization of thermal sprayed Si on sintered SiC for space optical applications
Published in Surface Engineering, 2021
Tayaramma D. P. V. Jalluri, S. Somashekar, Arjun Dey, R. Venkateswaran, S. Elumalai, B. Rudraswamy, K. V. Sriram
The CVD-coated SiC is the most sought after material for optics [12]. Reaction-bonded silicon carbide (RBSiC) is a two-phase material with SiC and pure Si [13]. However, the best surface micro-roughness achieved and reported is only 5 nm RMS. Deposition of additional layer of SiC on to the figured RBSiC is described by Johnson [14]. This method proposes an intermediate coating step that calls for additional polishing to attain a super smooth surface and is inherently limited by CVD-related intricacies. A similar intermediate coating method based on ion-assisted deposition of SiC has been demonstrated by Wang et al. [15]. Another solution suggested by Tang et al. [16] is to have thick coatings on SiC substrates either with PVD silicon or PVD SiC. Here again, the thickness of as-deposited SiC film is limited by the internal stress induced by differential thermal expansion of the film and substrate as well as deposition defects. A laser-based cladding approach to repair surface defects of silicon-infiltrated silicon carbide ceramic is reported by Lusquinos et al. [17] but limited to structural applications. Ding et al. [18] fabricated and tested successfully silicon modified layer by PVD over 450 mm SiC substrate by ion beam figuring and polishing. They have achieved the roughness of about 0.52 nm for the developed SiC aspheric mirror [18].
Laser powder bed fusion as a net-shaping method for reaction bonded SiC and B4C
Published in Virtual and Physical Prototyping, 2022
Sebastian Meyers, Miquel Turón Vinãs, Jean-Pierre Kruth, Jef Vleugels, Brecht Van Hooreweder
Manufacturing of these ceramic components generally relies on a powder metallurgy (PM) process where ceramic powder particles are first compacted or shaped to create a porous preform that needs densification to achieve full density and strength. Processing of carbide ceramics however is not straightforward, as traditional densification through solid-state sintering (SSS) is very challenging due to the covalent bonding and low diffusion coefficients. Grain growth is therefore promoted over densification, unless sintering aids are added for solid-state sintering or liquid phase sintering (Biswas 2009). An alternative faster and cheaper densification method is reaction bonding (RB), in which the initial porous powder preform, usually containing α-SiC (Chiang, Messner, and Terwilliger 1991) or B4C (Dariel and Frage 2012) and optional carbon (C) is infiltrated with liquid silicon (Si) at temperatures between 1450 and 1600°C, i.e. above the melting temperature of Si. The liquid Si infiltration (LSI) closes any residual porosity thanks to the good wettability of SiC and B4C by Si. Additionally, reaction formed β-SiC can be obtained during LSI according to the following reactions and depending on the constituents of the porous preform (Yurkov et al. 2018): The resulting material is a ceramic composite. Reaction bonded silicon carbide (RBSC) consists of original α-SiC, reaction formed β-SiC according to reaction [i] and residual Si. Reaction bonded boron carbide (RBBC) on the other hand is comprised of original B4C, reaction formed β-SiC according to reactions [i] and [ii], residual Si and a ternary B12(B,Si,C)3 compound according to reaction [ii]. Mechanical and thermal properties of these reaction bonded carbide ceramics heavily depend on the amount of residual Si in the final microstructure, as well as on the grain sizes of the SiC and B4C particles.