Inconel 718 Disc Springs: Material Characteristics, Applications, and Manufacturing Considerations

Inconel 718 (DIN 2.4668) is a precipitation-hardened nickel-based superalloy widely used for disc springs operating under demanding conditions. Its alloy matrix is primarily composed of nickel and chromium, with additions of iron, niobium, molybdenum, titanium, and aluminum. It achieves strengthening through precipitation phases. Its room-temperature elastic modulus is approximately 208,000 N/mm². With its balanced mechanical properties, it is one of the most readily available and widely applicable nickel-based materials for disc springs.

Key Material Advantages
1. High strength with excellent corrosion and oxidation resistance;
2. Stable fatigue performance and good mechanical stability;
3. Mature precipitation-hardening heat-treatment processes and a stable material supply chain.

Disc springs carry loads through bending stress and combined radial and axial stresses rather than simple axial tension. Therefore, they require strong resistance to repeated loading. Inconel 718 is suitable for applications requiring a combination of high strength, resistance to corrosive media, and medium-to-high-temperature service.

Typical applications include:
• Oil and gas equipment
• High-pressure process valves
• Chemical processing equipment
• Aerospace mechanical components
• Energy equipment

Manufacturing Control Considerations

Manufacturing Inconel 718 disc springs is considerably more demanding than manufacturing conventional spring-steel disc springs.

Raw materials must be supplied with material certificates and traceability documentation. The forming process must strictly control residual stresses to prevent dimensional drift. Heat treatment must be matched to the specific alloy grade to ensure the required yield strength, hardness, and fatigue properties.

Surface defects can become sources of fatigue cracks, so surface quality after forming requires particular attention.

Dimensional inspection should cover:
• Inside diameter
• Outside diameter
• Thickness
• Free height
• Flatness
• Cone angle

For critical products, load-deflection curves must be tested; dimensional inspection alone is insufficient.

Material Selection Limits

Inconel 718 provides balanced overall performance. However, under long-term high-temperature conditions where stress relaxation is the primary failure risk, its performance is inferior to Inconel X-750.

Material selection must therefore consider the actual operating temperature, stress level, and expected service life to confirm material suitability.