There are four key criteria for sizing and selecting a wave spring: load, working height, physical design requirements (bore diameter, ID, OD), and material.
In many cases, manufacturers supply custom wave springs in “exotic” materials or with special finishes to meet unique application demands, including difficult environments or corrosion resistance. And in some cases, appearance also plays a role in material and finish selection.
Wave spring materials
Material options for wave springs can be generally grouped into three categories: steels, superalloys, and coppers.
Steels include both carbon steel and stainless steel. Carbon steel wave springs are tempered to provide high tensile strength and yield strength. Wave springs made of carbon steel are readily available and cost-effective for applications where corrosion is not a concern or where the spring is submerged in a protective liquid or oil to prevent corrosion.
The most common stainless steel offering for wave springs is 17-7 stainless (similar to 302 grade stainless), which can withstand higher temperatures than carbon steel (up to 650° F) without losing its spring properties, due to precipitation hardening. 17-7 stainless is also suitable for applications where the spring will be subjected to high stress and high fatigue.
For applications in the food, medical, and chemical industries, as well as those where the wave spring will be exposed to seawater, wave spring manufacturers also offer 316 grade stainless steel, which has even higher corrosion resistance than 17-7 or 302 stainless.
Superalloys — sometimes referred to as “exotic” alloys — are metal alloys that provide high corrosion resistance and extreme heat tolerance. Despite the name, these so-called exotic alloys are often provided as standard offerings from wave spring manufacturers. One popular material for wave spring applications is a nickel-chromium alloy commonly known as Inconel X-750 (Special Metals), which can be provided in various forms offering heat resistance up to 1000° F.
Other superalloys for wave springs include a cobalt-nickel-chromium-molybdenum alloy known as MP35N (SPS Technologies) and a similar cobalt-chromium-nickel-molybdenum alloy known as Elgiloy (Elgiloy Specialty Metals). Both provide high strength, excellent fatigue strength, and excellent corrosion resistance, especially in acidic and saltwater environments. Similarly, Hastelloy C-276 (Haynes International*) is a nickel-molybdenum-chromium alloy with tungsten added, which provides good resistance against sulfur compounds such as sulfuric acid and chloride ions found in hydrochloric acid, hypochlorite and chlorine dioxide.
Elgiloy is most commonly used in the oil and gas industry, while MP35N is suitable for aerospace and medical applications, including implantable devices) Hastelloy C-276 is popular in chemical, wastewater, and seawater applications.
*Hastelloy C-276 is the name given to this material when it is manufactured by Haynes International. It is also known as Inconel C-276 when manufactured by Special Metals Corporation.
The most popular copper material for wave springs is beryllium bronze alloy 25, which has a low modulus of elasticity and high tensile strength, with good resistance to loss of physical properties at high temperatures. A less-expensive alternative is phosphorus bronze, although its performance falls short of beryllium bronze.
Wave spring finishes
Finishes for carbon steel
Since they have no corrosion protection, wave springs made of carbon steel material are provided with an oil dip finish for transport and storage. Carbon steel wave springs can also be provided with a black oxide finish, but black oxide is used only for cosmetic purposes since it doesn’t provide corrosion protection. Zinc phosphate (also referred to as “Parkerizing”) can also be applied as a finish to carbon steel wave springs, although zinc plating provides better corrosion resistance.
Finishes for stainless steel
Stainless steel wave springs are degreased, often using a combination of vapor degreasing and ultrasonic cleaning. For additional corrosion resistance, stainless steel can be supplied with a passivated finish, which dissolves iron and other particles embedded in the material’s surface.
Ultimately, the choice of wave spring material and finish will depend on the environment, life cycle expectations, lead time requirements, and budget. And with so many options for materials and finishes, it’s not difficult to find a combination that meets even the most extreme or unique application requirements.