High-temperature turbine blade rhenium content escalation

Around 2000, rhenium content in turbine blades reached 6%, driving blade cost to $6,000–8,000 each. The industry is now learning to take rhenium back out.

There are some molybdenum-rhenium alloys with very high temperature capability. Rhenium is a refractory and a platinum-group metal. These are the platinum-group metals along here. Ruthenium and rhodium — those guys all make what they call the platinum-group metals. We're getting rhenium out of turbine blades. I don't know if I told you the story that when I took my creep course from Professor Grant, who had developed a lot of these alloys, his first question in class was, what's the best material for making a high temperature turbine blade? We all guessed, nickel or cobalt. He says, no, platinum. Doesn't oxidize in the air, goes to 1700 degrees C, has excellent strength, easy to form. Only problem is, it costs too much. Well, rhenium was one of the cheaper platinum-group metals, and around 2000 we were getting to 6% rhenium in those turbine blades, which is why those turbine blades cost six, seven, eight thousand dollars apiece. 6% of them platinum-group metal. But they're learning to take the rhenium out.

CMSX-4 (~3% Re), CMSX-5 (~6% Re). Rhenium is a platinum-group metal; $1000–$2000 per ~1 lb pigtail sample. Tom recalls Nick Grant's class declaring platinum the ideal jet engine material — laughable then, no longer.

It's partly raw materials now in the engine business. To get these best single crystals, CMSX-4 was like a six percent rhenium alloy. Rhenium is a platinum group metal, pretty pricey. I remember taking Nick Grant's course. Nick Grant was a professor in this department. He made his career after World War II on high-temperature creep, and he was developing some of the alloys people were using. First day of class he came in and said, "What's the most creep-resistant material to make a jet engine out of?" We all started guessing about different alloys. He says, "Platinum. Melts at 1700 C. It's got a lousy density — density is important in a jet engine — but it doesn't oxidize at high temperatures, and platinum is the best metal." Of course it was all laughable, because everyone knew that platinum was too expensive to use in an engine.