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Few people have ever heard of rhenium — a rare and semi-precious metal — but it’s an important material in the aerospace industry. Modern jet engines require rhenium as an alloying element — critical to the performance of commercial, military and even rocket engines used for space exploration. Rhenium also happens to be one of the rarest elements on earth, mined mostly in the U.S, Chile and Kazakhstan. All engine manufacturers use it because it allows engines to reach higher temperatures required in jet flight and to consume less fuel when operating.
As a new feature story just published on GE’s Citizenship Web site – which we’ve excerpted here — explains in detail, for the past 10 years GE Aviation has been working to lessen its dependence on rare minerals, including rhenium. The work is being accomplished through a combination of innovative component designs, advanced manufacturing processes and new alloys. Recycling materials from unserviceable engine parts is also being practiced to reduce the need for rhenium as a raw material in jet engine manufacturing. Through the GE Reclamation Program, GE Aviation is producing better outcomes for GE, its customers and the environment, saving millions of dollars by using recycled material.
“The goal of the program is to recycle, reuse and replace this rare metal,” said Ted Grossman, chief manufacturing engineer, GE Aviation. “Not only will it help us reduce our need for rhenium and lower costs, it is reducing the environmental impact associated with mining activities and material disposal.”
When alloyed with other materials from the periodic table, rhenium helps create strong superalloys necessary for the manufacture of high-pressure turbine (HPT) blades used in jet engines today. As early as the 1980s, engine makers discovered that nickel-based alloys containing rhenium were able to retain their strength at extremely high temperatures, providing durability, wear and extended life for certain engine components.
Not only is rhenium extremely rare at an average concentration of two parts per billion in the earth’s crust, it is very difficult to extract. Rhenium is not mined, but rather recovered and extracted as a byproduct of copper mining. Very little rhenium is actually processed and isolated each year as compared to the millions of tons of copper and millions of pounds of molybdenum that are extracted from the same copper deposits.
To put this into perspective, consider the following scenario. It takes, on average, approximately 120 metric tons (264,554 pounds) — or the equivalent weight of 44 Cadillac Escalade SUVs — of copper ore to produce 1 ounce of rhenium — or the equivalent weight of five U.S. quarter coins. The production of one HPT blade requires about 0.5 ounces of rhenium. The extraction processes required to mine that material are significant, as are the environmental impacts and carbon emissions that go along with them
GE’s three-pronged approach involves recycling metal grindings from the manufacturing process; GE Aviation metallurgists and engineers developing alloys that require less or zero rhenium; and reclaiming rhenium from used engine parts.
The full story on GE.com/citizenship explains how customers such as the U.S. Navy, one of the first participants in the reclamation program, are reaping huge cost savings and how the GE Aviation team is currently working to expand the program.
Raring to go: An operator prepares materials for the reclamation process..