evanc3 t1_irpejoo wrote on October 10, 2022 at 12:48 AM

Reply to comment by gnusmas5441 in TIL that passenger jet engines produce most of their thrust from fan at the front, not from the jet exhaust, and that this is called a high-bypass engine. by Rilot

Plenty of materials that can do this, the trick is to get one that doesn't creep over time because the blade tips are remarkably close to the engine wall (tip clearance)

slater_just_slater t1_irq2fgg wrote on October 10, 2022 at 4:11 AM

Creep is why most 1st stage turbine blades are single crystal. Fun fact, single crystal blades are "grown" not cast.

They are also the most boring thing ever to look at under a metallograph.

evanc3 t1_irq2u47 wrote on October 10, 2022 at 4:15 AM

Still blows my mind!

But yeah I can imagine lol

slater_just_slater t1_irq4gst wrote on October 10, 2022 at 4:33 AM

What is interesting is that it's the same principle to how single crystal silicone is grown for microchip substrates. However the blades are hollow.

Since they have no grain structure, nothing responds to an acid etc, on a metallograph it's just a white blob.
They do have a thermal barrier coating (TBC) One of my jobs as a process engineer at Rolls Royce was the TBC coating. If you are bored here is a link about it.

evanc3 t1_irq4nd0 wrote on October 10, 2022 at 4:34 AM

I've actually worked in both industries! Very cool link though, I do thermal for aerospace currently but haven't come across these.

morreill t1_irscs1e wrote on October 10, 2022 at 5:48 PM

Very interesting read. Thank you !