Welding Techniques

The Realities and Best Practices of Working With Exotic Metals

Exotic metals fall outside the list of materials that are common to most manufacturing projects. Since they are rare and unfamiliar, they can be expensive and difficult to obtain. But the performance requirements of some projects can only be satisfied by these unusual materials. Most manufacturers avoid the risk associated with these projects, and the bold few who are willing to work with exotic metals have to leverage their experience and expertise to get it right the first time.

Why Use Exotic Metals?

Most manufacturers are familiar with common materials like carbon steel, austenitic stainless steel and structural aluminum grades. Some projects, however, call for the use of exotic metals like custom heat-treated steel or nickel-based superalloys, titanium, zirconium, hafnium, hastelloy and waspaloy.

Some of these metals are prized for their impressive strength-to-weight ratios. Others — such as nickel-based alloys that introduce chromium or niobium — are well-suited for high temperatures or corrosive environments, including oil and gas services, and pulp and paper mills. Since they are made for use in a single industry and designed to perform in a specific environment, they are not widely known outside of that industry, which makes them inherently exotic.

Some customers determine that only an exotic material can meet their performance requirements, but working with these rare materials is no easy task.

The Dangers of Exotic Metals

Exotic metals are expensive and can take a long time to obtain. A long lead time for some rare materials could be as much as six months or a year. In some cases, a mill has to produce the raw materials to order.

These considerations send most manufacturers running.

If they don't have the necessary background and experience, or if they aren't hyper-detailed in their planning, a manufacturer can waste months of work and hundreds of thousands of dollars in raw material expenditures on a single mistake.

The manufacturer that is bold enough to tackle the challenge, however, enjoys a competitive advantage in daring to take on work that their competitors can't or won't — but they must have the right procedures in place to make it work.

Best Practices in Working With a New Metal

Although the rarest materials will be unfamiliar to virtually all manufacturers, the most experienced will have worked with something similar in the past. So when working with a new metal, a manufacturer's first task is to develop a frame of reference by comparing and contrasting the similarities and differences between the metals they know and the new metal they don't know.

Manufacturers will predict the properties and behavior of the new material by comparing its performance with that of metals they use frequently. They will examine three main areas:

  • Machinability: The vendor will want to know how the new metal cuts, if it will cause excessive wear on their cutting tools, if it will remain stable or if it will move around when material is removed from it.

  • Pyrophorics: Is it a pyrophoric material whose chips and shavings can combust and cause a difficult fire? If so, the manufacturer will want to inform and train everyone involved and make sure they have the right kind of fire extinguishers on hand.

  • Welding: The vendor will have to determine if special techniques are necessary to produce a satisfactory weld. Is the material is prone to forming a hard oxide layer that makes it difficult to weld a pass over top of it? If so, the welding team will have to determine if it will be necessary to grind in between passes or shield the material to prevent an oxide from forming in the first place. Are there special controls that need to be put on temperature or heat input limits? Will the material require a post-weld heat treatment to meet the mechanical properties?

Exotic metals are rare, expensive, difficult to work with and hard to obtain. In some cases, however, they are the only materials capable of satisfying the performance needs of a critical-use project. When contractors go searching for a supplier with the confidence and experience to take on the challenge, however, they realize that the field is limited to a courageous few. The manufacturers who are up to the task are in a class by themselves — all alone with the responsibility, the risk and the pride that comes with successfully completing these difficult jobs.