Inconel 718 Canted Coil Springs with High-Temperature Corrosion Resistance and Efficient Load-Bearing Capacity

Introduction

In many sealing systems, canted coil springs—despite their small size—directly affect the sealing reliability and service life of the mechanical seal.For most standard operating conditions, 17-7PH stainless steel is sufficient. However, in harsh environments such as high temperatures, high loads, or corrosive media, an increasing number of engineers are turning to Inconel 718.So, is Inconel 718 definitely better than stainless steel?The answer is no.

For applications at room temperature, it may not offer significant performance improvements but will increase material costs; whereas under extreme conditions, the advantages of Inconel 718—including high-temperature strength, corrosion resistance, and fatigue resistance—truly come into play.Therefore, engineers should focus not on “which material is best,” but rather on “which material is best suited for the current operating conditions”.This article will analyze the performance characteristics of Inconel 718 helical springs in the context of typical applications and help you select the most appropriate material.

Learn more about our Canted Coil Spring solutions:https:Canted-Coil-Spring Product Details Page.

Why Do Standard Canted Coil Springs Lose Performance at Elevated Temperatures?

Many engineers have experienced the same situation:A sealing system performs well during room-temperature testing, but its sealing performance gradually deteriorates once it begins operating at elevated temperatures.The first assumption is often that the sealing material has degraded.

However, in many cases, the real issue lies in the Canted Coil Spring itself.As operating temperature increases, conventional spring materials may experience:

1. Elasticity is decreasing—it can no longer provide sufficient preload.
2. Resilience is declining—its ability to recover after prolonged stress is diminishing.
3. It is prone to deformation under prolonged pressure—it is difficult to return to its original shape even after the load is removed.
4. Insufficient sealing pressure—the sealing surfaces do not make a tight enough contact.

This ultimately leads to leaks—affecting the reliability of the equipment is seal.

In other words, the seal may still be in good condition, but the spring can no longer provide sufficient preload to maintain reliable sealing.This phenomenon is particularly common in high-temperature valves, aerospace hydraulic systems, oil and gas equipment, and chemical processing applications.

How Does Temperature Affect a Canted Coil Spring?

The following engineering reference illustrates how elevated temperature influences spring performance.
Reference Conditions

1. Continuous operating conditions; 25% spring deflection; air atmosphere; long-term static compression.
2. The information below is intended for engineering comparison only and should not be interpreted as certified product performance.
   

   Operating Temperature	Standard Stainless Steel Canted Coil Spring	Inconel® 718 Canted Coil Spring
   25°C	Stable preload	Stable preload
   150°C	Generally stable	Generally stable
   300°C	Noticeable increase in stress relaxation	Maintains stable elastic performance
   500°C	Generally not recommended for continuous service	Suitable for many high-temperature applications, depending on design conditions

   

Why Is Inconel 718 Better Suited for High-Temperature Canted Coil Springs?

Many technical articles simply describe Inconel® 718 as a high-strength or high-temperature alloy.

For design engineers, however, the more important question is:Why does it maintain reliable spring performance at elevated temperatures?

The answer lies in its metallurgical structure.

Inconel® 718 is a precipitation-hardened nickel-based superalloy. Its excellent high-temperature mechanical properties are achieved through strengthening precipitates (γ” and γ’ phases), allowing the material to retain strength and elasticity under elevated operating temperatures.Compared with conventional stainless steels, Inconel® 718 offers several engineering advantages:

1. Reduced spring preload
2. Increased stress relaxation
3. Permanent deformation after long-term compression
4. Lower sealing contact force
5. A higher risk of seal leakage

In other words, the seal may still be in good condition, but the spring can no longer provide sufficient preload to maintain reliable sealing.This phenomenon is particularly common in high-temperature valves, aerospace hydraulic systems, oil and gas equipment, and chemical processing applications.

How Does Inconel 718 Compare with Elgiloy and 17-7PH Stainless Steel?

One of the most common questions engineers ask is:”Should I choose Inconel® 718, Elgiloy®, or 17-7PH Stainless Steel?”The answer depends entirely on the operating environment.Each material has its own strengths, and none should be considered universally superior.The following table summarizes their typical engineering characteristics.

Reference Sources: Special Metals Inconel 718 Technical Data, Elgiloy Material Datasheets, AK Steel 17-7PH Stainless Steel Datasheets, and other publicly available engineering references.

Engineering Note: The recommended continuous operating temperatures shown above are general engineering guidelines rather than absolute material limits. Actual operating capability depends on heat treatment, applied load, service duration, environmental conditions, and overall system design.

The comparison clearly illustrates that:

1. For room-temperature and moderate-temperature industrial applications, 17-7PH Stainless Steel is often sufficient.
2. When corrosion resistance and fatigue performance are the primary concerns, Elgiloy is frequently the preferred solution.
3. For sustained high-temperature and high-load applications, Inconel 718 provides the greatest performance advantage.

Material selection should always be driven by application requirements—not simply by choosing the highest-grade alloy available.

Engineering Tip

Many engineers focus primarily on tensile strength when selecting spring materials.However, the long-term reliability of a Canted Coil Spring depends on several equally important factors:

1. Whether the operating temperature exceeds the recommended range
2. Long-term static compression
3. Exposure to corrosive media
4. Proper groove design
5. Appropriate compression ratio

Even the highest-performance alloy cannot compensate for poor system design.For this reason, experienced engineers evaluate the application first and the material second, rather than automatically selecting the most expensive alloy.

If you are unsure whether Inconel® 718 is the right material for your sealing application, our engineering team can help.Explore our products and technical resources:Canted Coil Spring SolutionsOur engineers can recommend the most suitable spring material and structural design based on your operating temperature, pressure, media compatibility, motion type, and expected service life.

When Is an Inconel 718 Canted Coil Spring the Right Choice?

After learning about the performance characteristics of Inconel® 718 Canted Coil Springs, many engineers ask the same question:If Inconel 718 performs so well, should every Canted Coil Spring be made from it?The answer is no.

Good engineering is not about choosing the most expensive material—it is about selecting the material that best matches the operating conditions.The ideal design balances performance, reliability, and cost.The following sections explain where an Inconel® 718 Canted Coil Spring provides real value and where other materials may be the better choice.

General Industrial Equipment: 17-7PH Stainless Steel Is Usually Sufficient

For applications operating under normal or moderately elevated temperatures, such as:

1. Automated production equipment—production lines, robotic arms, and other equipment.
2. Hydraulic equipment—hydraulic cylinders, hydraulic valves, and other systems.
3. Pneumatic equipment—pneumatic cylinders, pneumatic actuators, and other equipment.
4. Industrial machinery—various types of general-purpose machinery and equipment.

Standard sealing systems—most conventional packing seal applications

17-7PH Stainless Steel typically provides reliable spring force, good fatigue resistance, and excellent cost-effectiveness.In these applications, replacing it with Inconel® 718 rarely produces a significant improvement in service life but can substantially increase material costs.For most standard industrial sealing systems, optimizing groove design and spring deflection usually delivers greater performance improvements than upgrading the spring material.

High-Temperature Sealing Systems: Where Inconel 718 Shows Its Advantages

As operating temperature increases, the challenges extend beyond mechanical strength.Engineers must also consider:

1. Elasticity gradually decreases—it cannot maintain a stable preload over the long term.
2. Prolonged exposure to high temperatures causes a loss of elasticity—its ability to recover becomes increasingly poor.
3. Prolonged compression causes deformation—it is difficult to return to its original shape even after the load is removed.
4. The load-bearing capacity continues to decline—the support it provides becomes increasingly weaker.

These are precisely the conditions where Inconel 718 Canted Coil Springs excel.Because the alloy retains excellent mechanical properties at elevated temperatures, it continues to provide stable preload even during long-term service.

Typical applications include:

1. High-temperature valves
2. Gas turbine auxiliary equipment
3. Aerospace hydraulic systems
4. Engine sealing components
5. High-temperature testing eq uipment

Corrosive Environments Require More Than High Temperature Resistance

Temperature is only one part of the equation.The operating media can have an equally significant impact on spring life.If a Canted Coil Spring is continuously exposed to:

1. Seawater
2. Acidic solutions
3. Alkaline chemicals
4. Chloride-containing environments
5. Chemical processing fluids

corrosion resistance becomes a critical design consideration.Inconel 718 provides excellent overall corrosion resistance in many demanding environments.However, when corrosion resistance and resistance to stress relaxation are the primary concerns—and operating temperatures are relatively moderate—Elgiloy may also be an excellent engineering choice.

Recommended Materials for Typical Applications

Engineering Note: The recommendations above are intended as general design guidance. Final material selection should always consider operating temperature, system pressure, media compatibility, compression ratio, groove geometry, and required service life.

A Common Misconception: Higher Strength Does Not Always Mean Longer Service Life

Many engineers begin by comparing tensile strength or yield strength.While these properties are important, they do not determine the long-term reliability of a Canted Coil Spring by themselves.For example:

A sealing system operating continuously at approximately 80°C may show very little difference in service life between 17-7PH Stainless Steel and Inconel 718.

However, when the operating temperature approaches 500°C, stress relaxation in conventional stainless steel increases significantly, while Inconel 718 is able to maintain a much more stable spring load.This illustrates an important engineering principle:Material performance should always be evaluated within the actual operating environment—not in isolation.

Material Is Only One Part of the Design

Many premature spring failures are not caused by the material itself.Instead, they are often related to design or installation issues.Before upgrading the spring alloy, engineers should also evaluate the following factors.

1. Is the Compression Ratio Appropriate?

Excessive spring deflection increases internal stress, accelerates fatigue, and may result in permanent deformation.

2. Is the Groove Properly Designed?

Groove width, depth, and chamfer geometry all influence spring loading.Poor groove design can lead to:

1. Excessive localized stress on the spring can easily lead to stress concentration, shortening its service life;
2. Increased friction between the spring and the groove raises movement resistance, affecting the smooth operation of the equipment;
3. Accelerated wear on the spring’s surface causes its elasticity to decline over time, reducing its sealing performance;
4. The spring is prone to being scratched or crushed during installation, making assembly more difficult and potentially preventing it from functioning properly after installation.

3. Have the Operating Conditions Changed?

Many systems are modified during their service life.Higher temperatures, different process media, or increased operating pressure may require a different spring material than the one originally specified.

4. Manufacturing Quality Matters

Even when two springs are manufactured from Inconel 718, differences in heat treatment, dimensional tolerances, manufacturing precision, and quality control can significantly influence their long-term performance.Material selection is only one component of overall product reliability.

Quick Material Selection Guide

This table is intended as an initial selection guide only.Final material selection should always consider:

1. Operating temperature                                                    • Compression ratio
2. System pressure                                                                •Groove design
3. Process media                                                                   •Target service life

Frequently Asked Questions

Is Inconel 718 always better than Elgiloy?Not necessarily.

For applications involving very high temperatures and heavy mechanical loads, Inconel® 718 is often the preferred solution.For applications where corrosion resistance, fatigue life, and resistance to stress relaxation are the primary concerns, Elgiloy® may offer better overall performance.

Should I upgrade to Inconel 718 for a standard hydraulic system?

In most cases, no.For conventional hydraulic sealing applications operating at moderate temperatures, 17-7PH Stainless Steel is typically sufficient.Optimizing groove geometry and spring compression often provides greater benefits than selecting a higher-grade alloy.

Why can two springs made from the same material perform differently?

Material is only one factor.Heat treatment, manufacturing precision, dimensional tolerances, surface finish, and production consistency all contribute to the final performance of a Canted Coil Spring.

Conclusion

An Inconel 718 Canted Coil Spring is not a universal solution for every application.Instead, it is a high-performance spring material specifically suited for high-temperature, high-load, and demanding service environments.Successful spring design depends on more than material selection alone.Groove geometry, compression ratio, operating conditions, and manufacturing quality all play equally important roles in achieving long-term sealing reliability.If you are developing a new spring-energized sealing system or optimizing an existing design, our engineering team is ready to help.Explore more technical resources:Contact Our Engineering Team

Our engineers can recommend the most suitable Canted Coil Spring material and design based on your operating temperature, media, pressure, motion type, and service-life requirements, helping you improve product reliability while reducing total lifecycle costs.