Introduction

High-pressure applications push mechanical seals to their limits. Under extreme pressure, seal faces must maintain flatness, resist deformation, and prevent leakage. Not all materials can handle these demands. Silicon carbide, with its exceptional strength and rigidity, has become the standard choice for high-pressure mechanical seals. This article explains why.

Compressive Strength 

Silicon carbide has a compressive strength of approximately 3,900 MPa. This is among the highest of any engineering ceramic. For comparison, tungsten carbide compressive strength is approximately 3,000–4,000 MPa depending on grade, and alumina is approximately 2,400–2,500 MPa.

High compressive strength means the seal ring will not crush, deform, or yield under extreme pressure. The material maintains its dimensional accuracy even when subjected to thousands of pounds per square inch.

Elastic Modulus 

Elastic modulus (Young's modulus) measures a material's stiffness—its resistance to elastic deformation under load. Silicon carbide has an elastic modulus of approximately 420 GPa. This is higher than tungsten carbide (approximately 200–300 GPa depending on binder content) and much higher than steel (approximately 200 GPa).

For high-pressure seals, high stiffness is critical. Even minor elastic deformation of the seal face can create gaps that allow leakage. Silicon carbide's extreme rigidity ensures that the seal faces remain flat and parallel under pressure.

Resistance to Pressure-Induced Distortion 

In high-pressure applications, the hydraulic force acting on the seal can distort the seal ring. This distortion, known as coning or dishing, opens a gap between the seal faces and causes leakage. Materials with high elastic modulus resist this distortion.

Silicon carbide's exceptional stiffness makes it the material of choice for high-pressure mechanical seals. Even at pressures exceeding 3,000 psi, SiC seal rings maintain their geometry.

Surface Finish Stability

High-pressure sealing also requires extremely flat, smooth seal faces. Surface finish of 2–4 Ra microinches is typical. Silicon carbide can be polished to these finishes, and more importantly, the finish remains stable under pressure. Softer materials may deform microscopically, creating leakage paths.

Applications

High-pressure pump seals, hydraulic systems, compressor seals, and subsea equipment all benefit from silicon carbide seal rings. Any application with operating pressures above 1,000 psi should strongly consider SiC.

Need High-Pressure Seal Rings? 

At BSTEC, we manufacture silicon carbide seal rings rated for pressures up to 5,000 psi and beyond. Contact our engineering team to discuss your high-pressure sealing requirements.