Invar 36 spotlight

Invar 36, also known within the industry as Nilo 36, is a nickel-iron superalloy known for its low coefficient of thermal expansion. Containing 36% nickel, it maintains nearly constant dimensions, as well as good strength and hardness, over a wide range of temperatures. Invented in 1896 by Swiss physicist Charles Edouard Guillaume, Invar was created as a low-cost alternative to a metre once made of platinum and iridium. Guillaume's work led to the discovery of a relatively inexpensive iron-nickel alloy—a steel-like material that expands very little when heated. He named the alloy Invar because it was almost unchanging or "invariable."

Invar 36 success

One of our customers approached us specifically to use INVAR 36 for a component requiring the near-constant dimensions and long-term dimensional stability for which this alloy is known. Signicast engineers rose to the challenge, not only casting Invar 36 successfully but also completely exceeding the customer's expectations—all while saving them money.

Why did our customer need Invar 36? The slightest change in the dimensions or shape of their component could alter their end product—even though they were already in a temperature-controlled room. A few degrees could alter the function of the part. They knew they needed to work with a material like Invar 36, but machining it from solid material was costly.

How did Signicast help? We had never worked with Invar 36 before, but there has never been a challenge our engineers did not at least try to overcome. Through research and testing, we developed a casting material that performed as well as or better than wrought material, and we were able to cast it successfully to net shape. Not only did we reduce the final part cost because machining was not required, but our final part cost was actually lower than the cost of their original metal block—before machining.

The end result? A very happy customer who achieved tenfold savings and a new material added to our offerings.  

Invar 36 maintains nearly constant dimensions at temperatures below -150 degrees Celsius up to 260 degrees Celsius.

Who should use Invar 36?

Customers operating under strict temperature constraints will likely see the advantages of using Invar 36. Unfortunately, those currently machining from solid material may not realise that casting to net shape is also an option. Today, Invar 36 is often used in measuring devices, precision mechanical systems, laser components, thermostat rods, metres and components that transport liquefied gases—to name a few.

Invar industry applications

Invar can be used in a variety of applications within the aerospace, medical and consumer electronics industries. However, where superalloys with low CTE are beginning to outperform other metals is in automotive technologies. As autonomous vehicles grow in popularity, sensors, radars and cameras are becoming increasingly advanced and critical to vehicle function. LiDAR, an acronym for light detection and ranging, uses light waves from a laser to calculate how long it takes for light to strike an object or surface and reflect back to the scanner—determining the distance of surrounding objects. An alloy with near-constant dimensions and long-term dimensional stability, such as Invar 36, is extremely important in such intricate devices. Alternative alloys with low CTE, such as Kovar, are also viable options for casting LiDAR sensors. Investment casting is a cost-effective solution compared with machining LiDAR parts from solid material.

What are the advantages of Invar 36? 

The most obvious advantage of Invar 36 is its ability to maintain dimensions at cryogenic temperatures. In addition, Invar 36 looks and feels similar to steel. It also has outstanding weldability and machinability. Invar can also be produced with customised chemistries to better meet customers' strength and hardness requirements.