Custom Alloy 718 / Inconel 718 Disc Springs for HPHT Service

Why engineers move beyond standard spring steel

Standard spring steels can perform very well in normal industrial duty, but severe service changes the design equation. As temperature rises and exposure becomes more aggressive, relaxation resistance and environmental durability become just as important as room-temperature strength.

That is where Inconel 718 becomes attractive for critical Belleville washer stacks.

Where Inconel 718 Belleville washers are commonly used

Inconel 718 disc springs are frequently specified for applications such as HPHT valve systems, offshore tooling, gas turbine-adjacent equipment, aerospace hardware and petrochemical bolting systems that cannot tolerate rapid preload loss.

These are usually not price-driven purchases. They are reliability-driven purchases where maintenance cost, leakage risk or shutdown consequence is far more expensive than the alloy itself.

How custom Alloy 718 springs should be specified

Custom Alloy 718 springs should be specified around load curve, available space, heat treatment condition, temperature band and documentation needs rather than by alloy name alone. Requests for custom alloy 718 springs or Inconel 718 springs often come from buyers who already expect severe-service performance, but the engineering review still has to prove the spring geometry and stack behavior.

If the same project also mentions valve duty, offshore service or aerospace hardware, the quotation should clarify fatigue expectation, corrosion media and whether the spring works as a single washer, parallel set or combined stack.

Selection points for elevated-temperature spring packs

Simply switching material does not guarantee a good result. Spring geometry, operating deflection, stack arrangement and surface condition still control actual performance. Severe-service packs should be reviewed as a system rather than as loose washers.

Projects also need clarity on whether the priority is corrosion resistance, temperature capability, anti-relaxation behavior, fatigue life or a combination of all four.

• Confirm the target operating temperature band, not only the peak temperature.
• Review media exposure, chlorides, sour service or oxidation risk.
• Match the stack travel to the real joint movement and settling behavior.
• Validate load retention requirements over the maintenance interval.

When buyers should consider alternatives

If the service is mainly corrosion-driven at moderate temperature, certain stainless grades may be more economical. If the duty is mostly static and the environment is mild, standard spring steel can still be the right answer.

Inconel 718 becomes the stronger candidate when the design needs a premium balance of strength retention, fatigue capability and severe-environment durability.