Single Crystal Turbine Blades?

[Harmonic_Vibe]

This is something I've been wondering about for awhile. Normally I research stuff online or at the library, but in the spirit of ####'s "CA Aviation Challenge", I've decided to see what the guys and girls on this forum know about this:

 

I know (or at least I've always understood) that the crystalline structure of metal is the 'Achilles Heel' of the material. To eliminate this weakness they grow large crystals (I.E. No "internal" crystalline structure) and thence machine blades from these huge crystals.

 

How do they grow these crystals? I know some of the experiments in space were centered around this.

 

How big can they grow them? Can, or do they make whole turbine wheels out of these things?

 

Am I right about any of this?

 

What about ceramics?

 

Can Adrienne Clarkson really dissolve parliament? And if so, where do I apply for the job? (Just curious)

 

HV

[arctic_front]

Not really trying to answer your question, as I'm as equally intrigued by the idea of a single crystal, but I have seen some really amazing displays of metallurgy in the construction of turbine engine parts during a course at Garret in AZ. They showed us a 'secret' process in which they took a partially machined blank of, as I call it, unobtainium, and submerge this blank, or round solid disk of material, into a tank of milky-white liquid. after a period of time it emerges as a fully finished turbine wheel. We all were impressed, then they showd us a sample that had been half-immersed....and the part that was out of the liquid was un-touched, but the half that was inside the liquid was a fully finished T-wheel. They could not tell us how they did it, but they approximated the process to the opposite of "electro-plating". I still wonder how a liquid of any kind, can remove so prescisely, the material not needed, and leave behind a ready-to-install turbine wheel. I have heard of the single-crystal idea before, but would surely find it just as cool as the liquid dip process. Kudos to the learned men that dream up this stuff! by all accounts, these parts do seem to hold up ...seeing as you pilot-types are still around to chat it up on this forum...it must be working. Next time you meet a P.Eng that works on this stuff, give him a big hug and thank him...he earned his pay, and keeps us all alive. ( and we can lay awake at night wondering how they do it )

[Harmonic_Vibe]

I waited and waited for someone to enlighten me (no facetiousness intended) and finally looked it up myself. I'm now somewhat of an expert (cough...).

 

Here is a link to a one-paragrapher that describes the process in a nutshell... but there's lots of stuff on the web about this... technology never ceases to amaze me...

 

HV

 

P.S. Happy Thanksgiving!!!!!!!!!!!

 

http://torque.oncloud8.com/archives/000253.html

[Harmonic_Vibe]

They showed us a 'secret' process in which they took a partially machined blank of, as I call it, unobtainium, and submerge this blank, or round solid disk of material, into a tank of milky-white liquid.  after a period of time it emerges as a fully finished turbine wheel.  We all were impressed, then they showd us a sample that had been half-immersed....and the part that was out of the liquid was un-touched, but the half that was inside the liquid was a fully finished T-wheel.

Hey arctic_front... I have given this some thought... and engineers being engineers I think I know how they did it...

 

Take a time-exed turbine wheel... encase it in something much softer and subject to dissolution in an acid that won't have much effect on the wheel itself... call this material "unobtainium"... or "impossibilium"... or "preposteronium"... stage a demonstration wherein a billet of plain metal gets a bath and comes out as a fully formed turbine wheel... watch your share price rise...

 

HV

[Elvis]

Then sell it on E-Bay.

 

:elvis: :shock: :elvis:

[Winnie]

I think the process you are talking about is similar to what is called Photo-Etching. This is widely used in advanced plastic modelling, and is not very hard to do.

 

How to do it large scale however...

 

How long did the process take?