Reaction Bonded Silicon Carbide in Mechanical Seal

Size

custom

Other Attributes

Place of Origin	Zhejiang, China
Brand Name	CF
Model Number	Silicon carbide （RBSIC/SSIC）ring
Size	Custom Size
Density	3.05/3.2
Temperature	1500
Light band	within 2
Hardness	115

Packaging & Delivery

Package Type:

Standard export packing

Supply Ability

Supply Ability

10000 Piece/Pieces per Month

Product Details

Product Parameters

Brand Name	CF
Material	Silicon carbide （RBSIC/SSIC）
Style	Mechanical Seal
Density	3.05
Temperature	1500
light band	Within 2
Hardness	115
Standard or Nonstandard	Nonstandard

SIC Properties

Indicators	Atmospheric Sintering SIC (SSIC)					Reaction burning SIC (RBSIC)
Purity (%) (SIC content)	>97					≥90
Hardness (HRA)	>92					>90
Density (g/m3)	>3.1					>3.05
Elasticity modulus (MPA)	40					41.2
Tensile strength (MPA)	290					275
Bending strength (MPA)	500					430
Compressive strength (MPA)	3850					3000
Thermal conductivity (cal / cm.s. ℃)	0.38					0.30
Coefficient of thermal expansion (1/℃)	4×10-6					4.3×10-6
Heat-resistant temperature (the atmosphere)	1300℃					1650℃
Acid-resistant properties	Apply to any strong acid					Five times higher than hardness alloy
Ratio	0.14					/

Why Choose Us

OK, let's take a comprehensive and in-depth look at Reaction Bonded Silicon Carbide (RB-SiC), an advanced ceramic that plays a key role in high-performance mechanical seals and extreme working conditions.

Overview

Reaction bonded silicon carbide (also known as Siliconized Silicon Carbide or Si-SiC) is a composite material manufactured through a unique chemical reaction sintering process. It perfectly combines the excellent hardness, wear resistance, chemical inertness and high temperature resistance of silicon carbide (SiC) with the excellent toughness and complex shape forming ability provided by the free silicon (Si) infiltrated into it. This makes RB-SiC a highly competitive material choice in harsh friction, corrosion, high temperature and pressure environments, especially in the field of mechanical seals, and is often used in combination with carbon graphite, antimony-impregnated graphite or by itself.

1. Core Principle: Reaction Bonding Process

The manufacturing process of RB-SiC is the source of its performance and structural uniqueness:

1. Raw material preparation:

1. Main ingredients: High-purity α-silicon carbide (α-SiC) powder as a skeleton.

2. Molding aids: Add carbon source (such as carbon black, graphite powder, or carbon produced by pyrolysis of organic binder) to form a carbon skeleton.

3. Plasticizer/binder: facilitate molding.

2. Molding:

1. Common methods: Injection Molding (can achieve extremely complex near-net shapes), pressing (dry pressing, isostatic pressing CIP), extrusion or casting (slurry).

2. Key goals: Form a green body with precise size, internal carbon skeleton (continuous or dispersed), and necessary porosity (reserved channels for subsequent silicon infiltration).

3.Debinding:

1. Slowly heat to remove organic binders and plasticizers in the green body, leaving a porous structure composed of SiC particles and carbon skeleton with a certain strength. This step is critical to avoid cracking or deformation of the green body.

4.Pre-sintering:

1. Sometimes light sintering is performed at a lower temperature to increase the strength of the green body, facilitate handling and reaction sintering.

5.Reaction Sintering/Infiltration:

1.Core step!

2. Immerse the porous green body in molten silicon (Si) melt (> 1410°C, silicon melting point).

3.At high temperature (~1400°C - 1600°C) in an inert atmosphere (usually vacuum or argon):

1.Molten silicon (Si(l)) penetrates the pores and carbon skeleton network inside the green body by capillary action.

2.A chemical reaction occurs: Si(l) + C(s) (from the carbon skeleton) --> β-SiC(s).

3.This reaction generatesnewly formed β-silicon carbide (β-SiC)in situand combines with the existing α-SiC particles.

4.Unreacted molten silicon(silicon is not 100% reacted)fills the remaining pores and gaps.

6.Cooling:

1. Cooling is done under strict control to minimize residual stresses.

Results:

·Dense parts with a density close to the theoretical value (~3.10 g/cm³) are obtained.

·Microstructure: Consists of original α-SiC particles, newly generated β-SiC phase generated by the reaction, and free silicon (Si) phase that fills the remaining space. The free silicon content is usually between 5% and 15%.

· Seamless connection: The newly generated β-SiC acts as a "glue" that firmly combines the original α-SiC particles and the free silicon phase to achieve good integrity.

2. Material structure and microscopic composition

· Three phase composite:

1. α-SiC particles: Starting material that provides primary hardness, wear resistance, high melting point and chemical stability.

2. β-SiC grain boundary phase: Generated in situ by the Si + C -> β-SiC reaction, bonding the α-SiC particles and connecting the free silicon phase.

3. Free Silicon (Si) Phase: Unreacted silicon fills the last voids, giving the material excellent toughness, thermal shock resistance and thermal conductivity, and making the material easy to process (EDM).

· High density: The final density is usually in the range of 3.00 - 3.10 g/cm³, close to full density (>98% theoretical density).

· Low (near zero) open porosity: The residual pores are basically filled with free silicon, ensuring excellent sealing and corrosion resistance.

3. Key physical and mechanical properties

· High hardness:

o80 - 90 HRA (~1300 - 1600 HV). Although slightly lower than pressureless sintered silicon carbide (SSiC) or pressureless sintered silicon carbide (S-SiC) (up to 2600 HV+), it is significantly higher than tungsten carbide (WC) and most other metals/ceramics. Enough to provide excellent wear resistance.

· High flexural strength / fracture toughness:

o Flexural strength (MOR): 300 - 450 MPa. Better than many engineering ceramics.

o Fracture toughness (K₁c): ~3.5 - 4.5 MPa·m⁰.⁵. It is one of its main advantages! Much higher than SSiC (~2.5 - 3.5 MPa·m⁰.⁵), close to or even partially exceeding hot pressed silicon carbide. The free silicon phase can effectively prevent crack propagation, giving it excellent resistance to impact, mechanical stress and thermal stress. This is critical for sealing environments that are susceptible to impact or thermal shock.

·High elastic modulus:

o~380 - 410 GPa. High rigidity and minimal deformation under load, which is conducive to maintaining the flatness and parallelism of the sealing end face.

·High compressive strength:

o

2000 MPa. Able to withstand high closing forces of mechanical seals.

o

·Excellent thermal conductivity:

o~100 - 120 W/(m·K). Close to or slightly better than cobalt-based tungsten carbide (WC), significantly higher than nickel-based WC. Second only to diamond, copper, oxygen-free copper and some silicon carbide (such as pure SSiC about 120-150 W/(m·K)). Extremely important for mechanical seals: Can efficiently export friction heat, reduce end face temperature rise, and prevent liquid film vaporization, thermal deformation, thermal cracking and coking.

·Low Coefficient of Thermal Expansion:

o~4.0 - 4.5 × 10⁻⁶ /K. Very low! Approximately the same as graphite and many advanced ceramics. Excellent thermal stability, small dimensional changes when heated, helps maintain a stable seal gap and reduce thermal stress.

·High Melting Point:

oSiC component melting point >2700°C, free silicon melting point 1410°C. Use temperature is limited by the free silicon phase (upper limit of about 1400°C in air, higher in inert or vacuum). Short-term resistance to more than 1200°C.

·Reduced Density:

o~3.05 - 3.10 g/cm³. Significantly lower than tungsten carbide (WC: ~14-15 g/cm³) and most metals. Reduced inertial loads on high-speed rotating parts.Ideal matching: Carbon graphite (Carbon Graphite) or impregnated graphite (antimony impregnated Sb, furan resin impregnated, etc.) is the most commonly used and most reliable combination (hard-soft matching). Low friction, low wear and self-healing properties can be achieved.

Hard-hard pairing:

RB-SiC vs. RB-SiC: Doable but very careful. Lower friction coefficient than WC-WC combination (about 0.3-0.5). Must ensure: absolutely clean media, sufficient cooling/flushing (such as Plan 32), excellent flatness and centering, high surface finish, avoid dry friction. Commonly used in high pressure, high speed, clean conditions (such as API 682 Plan 53/54). Wear is usually greater than SiC-graphite pairing.

RB-SiC vs. SSiC/pressureless sintered SiC: Slightly better friction performance than SiC-SiC (due to the presence of free Si to provide minimal lubrication/plastic flow), is the choice for higher PV values and extreme conditions.

Avoid pairing with metal: prone to excessive wear of metal sealing rings.

Manufacturing advantages and limitations (derived from the process)

Core advantages:

Manufacturing complex shapes: Injection molding capability is the trump card of RB-SiC! It can manufacture extremely complex near-net shapes with internal flow channels, fine grooves (such as spiral grooves, groove weir composite grooves), thin-walled structures, flanges, special-shaped parts, etc. This is difficult to achieve with other high-performance SiC (such as SSiC, which can usually only sinter simple shapes and then machine them).

Low shrinkage: The dimensional change during reaction sintering is extremely small (the net dimensional change is usually within ±0.1%). The finished product has extremely high dimensional accuracy, which greatly reduces the subsequent finishing amount and cost.

Relatively low cost: Compared with the same level of pressureless sintered SiC (SSiC/NSSiC) or hot pressed silicon carbide (HP-SiC), RB-SiC has significant cost advantages, especially when manufacturing complex shaped parts. The process temperature is low (no need to exceed the SiC recrystallization temperature ~2100°C) and the energy consumption is low.

Machinability: The presence of free silicon phase enables precision machining such as drilling and grooving using electrospark machining (EDM), which is difficult or expensive to achieve with pure SSiC.

Limitations:

The presence of free silicon:

Limits its application in fluoride/hydrofluoric acid environments (fatal flaw).

In high temperature (>1400°C) oxidizing atmospheres, free silicon on the surface will preferentially oxidize to form a glassy SiO₂ film, which may peel off under extreme high temperature cycles, causing oxidation to penetrate deep into the interior (the long-term maximum use temperature is usually limited to 1200°C - 1350°C). Pressureless sintered SiC has a higher long-term temperature resistance limit in an oxidizing environment (~1600°C).

The hardness is slightly lower than that of SSiC.

Dark color: Gray-black (due to carbon and silicon), not gray-green or black like pure SSiC.

Typical application scenarios in mechanical seals

RB-SiC is widely used in sealing occasions with extremely harsh working conditions due to its comprehensive performance:

Strong chemical corrosive media:

Chemical processes: Pumps, reactors, and agitators for high-concentration sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid and mixed acids, fuming sulfuric acid, chlorine, wet chlorine, bromine, corrosive solvents (toluene, chlorobenzene), and hypochlorite solutions. (Be careful to avoid HF).

Chlor-alkali industry: Sealing of brine, chlorine treatment, and caustic soda (NaOH/KOH) solution (concentration and temperature need to be paid attention to). Strengths!

Petrochemical: Sulfur-containing oil products, acid gas scrubber pump seals, amine liquid (MDEA, DEA).

Media with high wear resistance requirements:

Slurry pump seals containing solid particles or crystals (such as phosphate slurry, titanium dioxide slurry, coal slurry, catalyst slurry, wastewater sludge). Its wear resistance is several to dozens of times that of WC and Al2O3.

Pulp and paper industry: seals for black liquor and white liquor pumps containing abrasive fibers.

High temperature and high pressure:

Seals for hot oil, molten salt, molten sulfur, high temperature hot water (>200°C), and steam condensate systems.

Seals for high pressure pumps and compressors (need to be combined with high pressure resistant structural design).

Special industries:

Pharmaceuticals and biotechnology: high cleanliness requirements, resistance to CIP/SIP cleaning agents.

Flue gas desulfurization (FGD).

Nuclear industry (specific inert coolants).

Metallurgy: seals for aluminum liquid delivery pumps (RB-SiC is the preferred material! It is extremely inert to aluminum liquid and has good thermal shock resistance).

Pairing method:

RB-SiC (hard ring) vs. antimony-impregnated graphite / furan-impregnated graphite / resin-impregnated graphite (soft ring): the most common and reliable application combination.

RB-SiC vs. RB-SiC / SSiC (hard-hard): Used in harsh conditions with extremely high pressure, speed or easy crystallization leading to soft ring blocking, and strict operating conditions are required.

RB-SiC vs. WC (hard-hard): Not as common as SiC-graphite or SiC-SiC.

Key points for design, selection and use

Preferred hard-soft pairing: Unless extremely high pressure and high speed and the medium is extremely clean, it is strongly recommended to use RB-SiC with high-quality graphite (antimony impregnation is the best choice).

Pay attention to free silicon restrictions:

Absolutely prohibited in fluorine/fluoride environments! The medium composition must be thoroughly confirmed.

High temperature oxidation limit: In air or oxygen-rich environments, the long-term operating temperature is recommended to be no higher than 1200°C. Frequent start-stop thermal cycle environments require more conservative design.

Strongly oxidizing molten salts (such as nitrates) may corrode the silicon phase.

Take advantage of complex structures: Use its injection molding capabilities to design built-in cooling channels, optimized fluid dynamic grooves, etc.

Quality of sealing end face: High flatness (usually within 3 light bands) and low surface roughness (Ra < 0.1 μm) are required.

Cooling and flushing: Even if the thermal conductivity is good, when high pressure (P) and high speed (V) lead to high PV values, sufficient cooling/flushing must be provided (select the appropriate Plan according to standards such as API 682, such as Plan 11, 21, 31, 32, 52, 53, etc.) to prevent thermal cracking and failure.

Installation alignment: Similar to other ceramics, high installation accuracy is required to avoid impact and uneven force

4. Chemical and tribological properties

·Excellent chemical corrosion resistance:

oOverall strong inertness: RB-SiC shows excellent resistance in strong acids (concentrated sulfuric acid, concentrated nitric acid, concentrated hydrochloric acid, mixed acid), strong alkalis (concentrated sodium hydroxide, concentrated potassium hydroxide), salt solutions, and oxidizing media. The corrosion resistance range is very wide.

oBetter than tungsten carbide (WC): It does not contain easily corroded metal binders (such as cobalt and nickel). It hasunparalleled advantages in strong acids and strong oxidizing media (such as chlor-alkali industry, wet chlorine, and high-temperature concentrated sulfuric acid) that WC has difficulty in dealing with.

oBetter than graphite: It has higher strength and hardness, and is more stable in strong oxidizing acids (such as boiling concentrated nitric acid).

oKey limitations: hydrofluoric acid (HF)/fluoride and strong oxidizing alkali melt:

§HF/fluoride: The natural enemy of all silicon-containing materials (including RB-SiC, SSiC, etc.)! Silicon phases (Si and SiC) will be severely corroded and dissolved: SiO₂ + 4HF -> SiF₄↑ + 2H₂O, Si + 4HF -> SiF₄↑ + 2H₂, SiC + 4HF -> SiF₄↑ + CH₄?. Absolutely avoid contact!

▪Strongly oxidizing alkali melts: Such as molten nitrates/nitrites (>500°C), high concentrations of caustic soda (>30%, >100°C), the silicon phase will be oxidized and corroded.

·Excellent thermal/chemical stability: Stable in high temperature non-oxidizing atmosphere (inert, vacuum) or reducing atmosphere.

·Friction and wear properties (wear resistance):

oExcellent wear resistance: High hardness ensures its superb resistance to abrasive wear and adhesive wear. Particularly suitable for media containing solid particles.

oLow friction: A thin silicon-based oxide film (in air) is easily formed on the surface, which helps to reduce the friction coefficient with suitable counter surfaces.

oExcellent galling resistance: High thermal conductivity and heat resistance make it less prone to galling under dry start or boundary lubrication conditions.

oImportant matching principles:

▪Ideal matching: Carbon graphite orimpregnated graphite (antimony Sb, furan resin, etc.) is the most commonly used and most reliable combination (hard-soft matching). Low friction, low wear and self-healing can be achieved.

▪Hard-hard matching:

▪RB-SiC vs. RB-SiC: Doable but very careful. Lower friction coefficient than WC-WC combination (about 0.3-0.5). Must ensure: Absolutely clean media, sufficient cooling/flushing (such as Plan 32), excellent flatness and centering, high surface finish, avoid dry friction. Commonly used in high pressure, high speed, clean working conditions (such as API 682 Plan 53/54). Wear is usually greater than SiC-graphite pairing.

▪RB-SiC vs. SSiC/pressureless sintered SiC: Slightly better friction performance than SiC-SiC (due to the presence of free Si to provide trace lubrication/plastic flow), it is the choice for higher PV value and extreme working conditions.

▪Avoid pairing with metal: It is easy to cause excessive wear of metal sealing rings.

5. Manufacturing advantages and limitations (derived from process)

·Core advantages:

oManufacturing complex shapes: Injection molding capability is the trump card of RB-SiC! It can manufacture extremely complex near-net shapes (Near-Net Shape) with internal flow channels, fine grooves (such as spiral grooves, groove weir composite grooves), thin-walled structures, flanges, special-shaped parts, etc. This is difficult to achieve with other high-performance SiC (such as SSiC, which can usually only sinter simple shapes and then machine them).

oLow shrinkage: The dimensional change during reaction sintering is minimal (net dimensional change is typically within ±0.1%). The finished product has extremely high dimensional accuracy, which greatly reduces the amount and cost of subsequent finishing.

oRelatively low cost: Compared with the same level of pressureless sintered SiC (SSiC/NSSiC) or hot pressed silicon carbide (HP-SiC), RB-SiC has a significant cost advantage, especially when manufacturing complex-shaped parts. The process temperature is low (no need to exceed SiC recrystallization temperature ~2100°C) and energy consumption is low.

oMachinability: The presence of free silicon phase enables it to be precisely processed using electro-discharge machining (EDM) for drilling, grooving, etc., which is difficult or expensive to achieve with pure SSiC.

·Limitations:

oThe presence of free silicon:

§Limits its application in fluoride/hydrofluoric acid environments (fatal defect).

▪ In a high temperature (>1400°C) oxidizing atmosphere, free silicon on the surface will preferentially oxidize to form a glassy SiO₂ film, which may peel off under extreme high temperature cycles, causing oxidation to penetrate deep into the interior (the long-term maximum use temperature is usually limited to 1200°C - 1350°C). Pressureless sintered SiC has a higher long-term temperature resistance limit in an oxidizing environment (~1600°C). ▪ Hardness is slightly lower than SSiC. o Dark color: Gray-black (due to carbon and silicon), not gray-green or black like pure SSiC. 6. Typical application scenarios in mechanical seals

RB-SiC is widely used in sealing occasions with extremely harsh working conditions due to its comprehensive performance:

·Highly chemically corrosive media:

oChemical processes: Pumps, reactors, and agitators for high-concentration sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid and mixed acids, fuming sulfuric acid, chlorine, wet chlorine, bromine, corrosive solvents (toluene, chlorobenzene), and hypochlorite solutions. (Be careful to avoid HF).

oChlor-alkali industry: Seals for brine, chlorine treatment, and caustic soda (NaOH/KOH) solutions (concentration and temperature need to be paid attention to). Strengths!

oPetrochemical: Sulfur-containing oil products, acid gas scrubber pump seals, amine liquid (MDEA, DEA).

·Media with high wear resistance requirements:

o Slurry pump seals containing solid particles or crystals (such as phosphate slurry, titanium dioxide slurry, coal slurry, catalyst slurry, wastewater sludge). Its wear resistance is several to dozens of times that of WC and Al2O3.

o Pulp and paper industry: black liquor and white liquor pump seals containing abrasive fibers.

·High temperature and high pressure:

o Hot oil, molten salt, molten sulfur, high temperature hot water (>200°C), steam condensate system seals.

o High pressure pump and compressor seals (need to be combined with high pressure resistant structure design).

·Special industries:

o Pharmaceuticals and biotechnology: high cleanliness requirements, resistance to CIP/SIP cleaning agents.

o Flue gas desulfurization (FGD).

o Nuclear industry (specific inert coolants).

o Metallurgy: aluminum liquid delivery pump seals (RB-SiC is the preferred material! Extremely inert to aluminum liquid, good thermal shock resistance).

·Matching method:

oRB-SiC (hard ring) vs. antimony-impregnated graphite / furan-impregnated graphite / resin-impregnated graphite (soft ring):The most common and reliable application combination.

oRB-SiC vs. RB-SiC / SSiC (hard-hard): Used in harsh conditions with extremely high pressure, speed or easy crystallization leading to soft ring blocking, and strict operating conditions are required.

oRB-SiC vs. WC (hard-hard): Not as common as SiC-graphite or SiC-SiC.

7. Key points for design, selection and use

·Preferred hard-soft pairing: Unless extremely high pressure and high speed and the medium is extremely clean, RB-SiC and high-quality graphite (antimony impregnation is the best choice) are strongly recommended.

·Pay attention to free silicon limit:

oAbsolutely prohibited in fluorine/fluoride environments! The medium composition must be thoroughly confirmed.

oHigh temperature oxidation limit: In air or oxygen-rich environments, the long-term operating temperature is recommended to be no higher than 1200°C. Frequent start-stop thermal cycle environments require more conservative design.

o Strongly oxidizing molten salts (such as nitrates) may corrode the silicon phase.

·Make full use of the advantages of complex structures: Use its injection molding capabilities to design built-in cooling channels, optimized fluid dynamic grooves, etc.

·Quality of the sealing end face: Requires high flatness (usually within 3 light bands) and low surface roughness (Ra < 0.1 μm).

·Cooling and flushing: Even if the thermal conductivity is good, when high pressure (P) and high speed (V) lead to high PV values, it is necessary to provide sufficient cooling/flushing (select the appropriate Plan according to standards such as API 682, such as Plan 11, 21, 31, 32, 52, 53, etc.) to prevent thermal cracking and failure.

·Installation and centering: Similar to other ceramics, high installation accuracy is required to avoid impact and uneven force.

·Friction pair matching: Avoid using it in pairs with soft metal sealing rings (such as Stellite alloy) to avoid excessive wear of the metal ring.

8. Advantages Summary

1. Outstanding corrosion resistance: It is extremely resistant to most strong acids, strong bases, salts and oxidants (except HF).

2. Excellent wear resistance: It has superb resistance to abrasive wear and adhesive wear.

3. Extraordinary toughness: The fracture toughness ranks among the top engineering ceramics, and the impact resistance and thermal shock resistance (thanks to free silicon) are far superior to pure SiC (SSiC).

4. High thermal conductivity: Efficient heat dissipation is the guarantee of safe operation of the seal.

5. High temperature stability: It can work at high temperature (inert/vacuum>1400°C, air~1200°C).

6. Low thermal expansion coefficient: Excellent dimensional stability.

7. Complex shape capability: The injection molding process has huge advantages! It can realize complex sealing ring structures that cannot be manufactured by traditional SiC.

8.High dimensional accuracy & low shrinkage: Near net shape, low finishing cost.

9.Relative cost-effectiveness: While achieving high performance, the cost is lower than pressureless sintered SiC (SSiC/NSSiC) and hot pressed SiC.

9. Disadvantages/Limitations

1.Fluoride/hydrofluoric acid (HF) natural enemy: Absolute fatal defect, no contact.

2.High temperature oxidation limitation: The performance is not as good as pure SSiC/NSSiC under continuous oxygen-rich high temperature (>1400°C).

3.Hardness is slightly inferior to pure SSiC/sintered SiC: RB-SiC hardness is about 1300-1600 HV, while high-quality SSiC can reach 2500-2800 HV.

4.Electrochemical corrosion (only when there is free Si phase and in contact with electrolyte): In the electrolyte (such as salt water), silicon (anode) and SiC (cathode) form a corrosion couple, which may cause the silicon phase to dissolve. Selecting fully dense SiC (SSiC) or ensuring a good surface oxide layer can alleviate this. Pay attention to the potential risks in a strong electrolyte environment.

5.Single color (dark): Not as beautiful as some materials (usually not the main consideration).

10. Comparison with other high-performance sealing surface materials

·VS Pressureless Sintered Silicon Carbide (SSiC / Sintered SiC / S-SiC):

oRB-SiC: Higher toughness, better thermal shock resistance, can be made into complex shapes, can be processed by EDM, and lower cost.

oSSiC: Slightly higher ultimate hardness (more wear-resistant), high maximum purity (free of free Si), ultra-high chemical inertness (especially slightly stronger to HF, but still afraid of HF), better ultra-high temperature oxidation stability (long-term 1600°C), fine grains and more uniform structure. Usually limited to simple shapes, diamond processing is required, and the cost is high.

·VS Tungsten Carbide (WC):

oRB-SiC: More corrosion-resistant (especially strong acids and oxidizing media), lower density, higher hardness, no metal binder, equivalent or slightly better thermal conductivity. The cost may be equivalent or higher.

oWC: Especially good toughness (cobalt-based), compressive strength may be slightly higher, alkali resistance (especially nickel-based) is generally better, not resistant to strong acids and oxidation. Susceptible to selective corrosion by binders.

·VS Alumina Ceramic (Al2O3):

oRB-SiC: Fully rolled! Hardness, strength, toughness, thermal conductivity, corrosion resistance (except HF), and thermal shock resistance are significantly superior. Higher cost.

·VS Graphite/Carbon Graphite (Soft Ring):

oRB-SiC: Complementary to hard ring. Graphite is self-lubricating, low-friction, self-healing but has low strength, is easily eroded, has poor oxidation resistance, and is not resistant to strong acids.

Summary and comparison: RB-SiC is the most tough, most suitable for manufacturing complex shapes, and the most cost-effective high-performance SiC material. It provides top-level comprehensive performance in terms of resistance to corrosion, wear, high temperature, and thermal shock. When the application does not involve fluorides and is not exposed to extreme oxidizing high temperature environments (>1400°C) for a long time, especially when the sealing ring design is extremely complex (such as built-in fine cooling grooves, spiral grooves), RB-SiC is often the best or only solution. For extreme working conditions with ultra-high hardness and temperature resistance requirements, pressureless sintered SiC (SSiC/NSSiC) is more suitable. Tungsten carbide is superior in scenarios where hydrocarbons, non-corrosive media, and excellent toughness and impact resistance are required.

Conclusion

Reaction-sintered silicon carbide (RB-SiC) is an excellent engineering ceramic composite synthesized through a sophisticated chemical reaction process. It perfectly combines the hardness and chemical inertness of silicon carbide with the toughness and processability of free silicon. Unparalleled chemical corrosion resistance (avoiding HF), outstanding wear resistance, excellent thermal shock resistance and toughness, excellent thermal conductivity, and the ability to achieve complex geometries through injection molding make RB-SiC one of the top materials for mechanical seal rings under harsh conditions. Whether in strong acid pumps, corrosive slurry pumps, high-temperature hot oil systems, or applications requiring complex cavity seal designs, RB-SiC has demonstrated extraordinary reliability and long life. Despite the Achilles' heel of fluorinated materials and their limitations in high temperature oxidation, they have established an unshakable key position in many demanding industrial sealing challenges. Their unique combination of process and performance ensures their continued success and wide applicability in the field of advanced material sealing.