Real talk I cast turbine blades for IGT and Aerospace (not an engineer, just a floor worker). It was my impression that inside those turbines is an incredibly hostile environment (hot, acidic, g-forces), and still we cast them. We did some single crystal stuff for the really demanding parts. Is cast metal really that flawed?
No, but metallurgy isn’t a straightforward peocess like they were kinda implying. Gears, especially extremely high performance ones like in aerospace, have partial hardening, surface treatments, even exotic things like mixed alloys to ensure they meet the mechanical demands required of them. You can’t simply cast a gear and expect it to work - in this case if you tried as they were describing you’d likely just have the teeth shear when you tried to take off and you’d be fine, but there’s a real good reason that part costs as much as it does and it’s not just the administrative costs that come with aviation part documentation requirements.
Casting itself is fine for many applications, and advanced casting techniques are incredibly complicated and suitable in one form or another for many applications, but not all things should be cast.
Oh, I love how rabbit-holey metallurgy can get. One of my favorite topics is the processes used to cool hardened gears that have to be ground. Keeping the temperatures below a certain point so that they don’t lose the temper is surprisingly difficult even with external flood cooling (or working fully submerged), so you wind up with insane looking profile cutters that have cooling lines built into them directly.
Also the techiques to monitor the diameter of abrasive grinding tools get wild, like monitoring the capillary pressure of the coolant spray and similarly insane feats of precision.
That cutter is fucking art. The blades we ran had a ceramic core. Then the wax mould over the ceramic. Lose the wax, cast, then beat the shit out of it till the ceramic comes out the blade, now there are cooling channels built into the cast. Complex geometries too.
I was asking why the blades needed a ceramic coating before going into the turbine. Surely we could just heat treat the blades to whatever hardness required.
I was then informed that inside turbines it’s so hot the Hydrocarbons split up to free Hydrogen ions and the left over. The ceramic is there because it’s a highly acidic environment.
Actually that story is my go to “how to mentor story”. I asked why we coated the blades in ceramics. The engineer told me it was really hot in there and just waited for me to twig. I didn’t, then he said it was so hot hydrocarbons break up into free hydrogen and the rest, and then waited. Then I caught on, I have no doubt if I hadn’t then he would have said “free Hydrogen is the literal definition of an acid” and waited. Then “Acid eats metals like titanium alloys” wait. “Then Acid doesn’t eat ceramics” wait. I genuinely try to lead people to answers that way just because the way he made my dumbass feel like the smartest tool in the room. Actually, I asked why we pre finished the blades to near mirrors just to acid etch them dull again, and was told it was for the ceramic coating.
In some past aerospace work, I’ve seen requirements where, if you do use cast parts, you have to cast extra parts on each lot to use for destructive testing. Specifically to inspect the cross sections for flows or grains or whatever they want to look at.
Back maybe 25 years ago I got to tour inside Howmet in Whitehall, MI as part of a class. They did casting of turbine vanes for jet engines. Damned impressive process, and thorough quality checks x-raying every one for flaws. Finding out that each vane has coolant channels cast in was interesting, and a bit unnerving, since they get operated at temperatures above the melting point of the metal! I always think about that when I get on a plane.
Those orphans aren’t orphans any more… Progress.
Real talk I cast turbine blades for IGT and Aerospace (not an engineer, just a floor worker). It was my impression that inside those turbines is an incredibly hostile environment (hot, acidic, g-forces), and still we cast them. We did some single crystal stuff for the really demanding parts. Is cast metal really that flawed?
Out of all of the things that you would want to be comfortable with taking risks on, the Jesus Nut on a helicopter is not one of them.
There are no fallbacks if that fails.
The only thing that can save you is a miracle from our Lord and Savior, Jesus Christ, if the Jesus Nut fails on your helicopter while you’re in air.
No, but metallurgy isn’t a straightforward peocess like they were kinda implying. Gears, especially extremely high performance ones like in aerospace, have partial hardening, surface treatments, even exotic things like mixed alloys to ensure they meet the mechanical demands required of them. You can’t simply cast a gear and expect it to work - in this case if you tried as they were describing you’d likely just have the teeth shear when you tried to take off and you’d be fine, but there’s a real good reason that part costs as much as it does and it’s not just the administrative costs that come with aviation part documentation requirements.
Casting itself is fine for many applications, and advanced casting techniques are incredibly complicated and suitable in one form or another for many applications, but not all things should be cast.
It was me kinda implying it. Just making a shit posting comment in a shit post community.
Oh lol, mixed up you and bizarroland.
Is fine. Didn’t think I’d TIL on a shitpost comm, but you sent me down a wikihole. Always fun
Oh, I love how rabbit-holey metallurgy can get. One of my favorite topics is the processes used to cool hardened gears that have to be ground. Keeping the temperatures below a certain point so that they don’t lose the temper is surprisingly difficult even with external flood cooling (or working fully submerged), so you wind up with insane looking profile cutters that have cooling lines built into them directly.
Also the techiques to monitor the diameter of abrasive grinding tools get wild, like monitoring the capillary pressure of the coolant spray and similarly insane feats of precision.
That cutter is fucking art. The blades we ran had a ceramic core. Then the wax mould over the ceramic. Lose the wax, cast, then beat the shit out of it till the ceramic comes out the blade, now there are cooling channels built into the cast. Complex geometries too.
I was asking why the blades needed a ceramic coating before going into the turbine. Surely we could just heat treat the blades to whatever hardness required.
I was then informed that inside turbines it’s so hot the Hydrocarbons split up to free Hydrogen ions and the left over. The ceramic is there because it’s a highly acidic environment.
Actually that story is my go to “how to mentor story”. I asked why we coated the blades in ceramics. The engineer told me it was really hot in there and just waited for me to twig. I didn’t, then he said it was so hot hydrocarbons break up into free hydrogen and the rest, and then waited. Then I caught on, I have no doubt if I hadn’t then he would have said “free Hydrogen is the literal definition of an acid” and waited. Then “Acid eats metals like titanium alloys” wait. “Then Acid doesn’t eat ceramics” wait. I genuinely try to lead people to answers that way just because the way he made my dumbass feel like the smartest tool in the room. Actually, I asked why we pre finished the blades to near mirrors just to acid etch them dull again, and was told it was for the ceramic coating.
In some past aerospace work, I’ve seen requirements where, if you do use cast parts, you have to cast extra parts on each lot to use for destructive testing. Specifically to inspect the cross sections for flows or grains or whatever they want to look at.
Back maybe 25 years ago I got to tour inside Howmet in Whitehall, MI as part of a class. They did casting of turbine vanes for jet engines. Damned impressive process, and thorough quality checks x-raying every one for flaws. Finding out that each vane has coolant channels cast in was interesting, and a bit unnerving, since they get operated at temperatures above the melting point of the metal! I always think about that when I get on a plane.
Dead orphans are still orphans.