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Super Hard Steel
Sub_Dude writes: "Seems the folks at a Dept. of Energy lab have come up with a way to coat steel to make it harder. The process might be interesting to mechanical engineers out there, and because the article mentions nanotechnology, Hemos will like it. The press release is here, and an award for being "one of this year's top 100 technological achievements" is here."
Dictionary.com might agree with you, almost. But I would consider it to be technology on the scale of a billionth of a meter. So I prefer a more liberal interpretation. Certainly the materials are nanoscale, nanophase, and state of the art. I wonder if you'd feel the same about nanoarchitectured materials?
I am afraid that you are incorrect. Diamonds for examply are incredibly hard but are also extremely brittle and hence are not used in places where structural strength is required.
This is where it gets fun. You're confusing hardness or strength (they ARE interchangable ask ASM or your favorite Mechanics of Materials textbook), and Toughness. Toughness is the ability of a material to resist cracking, or if you prefer how brittle it is. Diamond is most certainly the king of strength, but, as you astutely observed, is brittle. Sillicon Carbide, carbon fiber, as well as glass share this quality. Again, I can't stress this enough, don't take my word for it. Tell me I'm full of shit, goto this website and find out for yourself.
Unfortunately the actual article made no such claims. They did not invent a stronger steel. They merely invented an extremely durable coating which bonds to steel. Sort of like a "super paint" actually.
They did invent a stronger steel. It happens to be a coating, but with a strength of I think 16 GPa, which is about 16 times better than a typical high strength structural steel and in the realm of about theoretical. Considering they believe the coating to be all but free of defects, this actually makes a lot of sence, as it is the defects which start the cracks that limit the strength of a material.
But it's funny, how people are. I prefer a liberal interpretation of nanotechnology, but ridgedly adhere to the indoctrination I was educated under. In anycase it certainly seems the press release was written with a reader like me in mind, and in so far as that was a good choice, it is correct. I would have expected it to have less resistance to chemical corrosion, but material science can be counter intuitive. In anycase I'm sure Powell's has at least a few good books on mechanics of materials if you're into that kinda thing.
--Jimmy has fancy plans; and pants to match.
As far as hardness and strength. They harder a material is the stronger it is. The actual relation isn't trivial to derive and depends on things like the tip you use for intentation, qualitatively, it isn't that difficult to grasp so I'll do my best to explain. Strength is the ability of a material to resist plastic deformation. Plastic deformation is when you stretch a material and it won't snap back, as opposed to elastic deformation where it will. Try bending a paper clip, very little at first, it will snap back like you never touched it. Now bend it around. Where you bent it, the bumps and twists, are now harder and resist bending more than the rest of the paper clip and make it look irregular. That's plasitically deformed. It won't ever be like it was unless you remake the paper clip. If you bend it a little more it should get a little bit harder, then stiff and easy to break. That's a qualitative stress-strain curve you can feel. Then same thing happens when you push an indentor into a material, some of it gets pushed out of the way to make room for the indentor, which isn't all that different from bending the paper clip. In fact hardness is so closely related to the strength of a material you can do a surface hardness test to find out what alloy something is made of without destroying it. One of those things. On the other hand, this is a coating, so it's always on the surface of something, and in that sence you're right. Hard coatings typically need less lubrication, experience less fretting (a form of mechanical corrosion), etc. They also mention that it has self-sharpening characteristics. So it might find its way into new anti-armor weapons, or just the sharper image catalog.
Yeah I would say this is front page stuff. Getting a metal to come near the theoretical ideal in strength is pretty impressive. This is at least as front page as anything else up there. A good overview of thermal spray can be found here.
--Jimmy has fancy plans; and pants to match.
Those metals have something else that makes them expensive: machining. They are hard metals, and it costs a lot of money to make something out of them. Of course, if we have cheap super hard steel, then we can make machine tools out of it, and cutting titanium won't be any problem. Then, you get to figure out how to make welding titanium cheap and easy.
I think right now, I'd love to see someone make a good turbopump out of this super hard steel. But with our luck, the inventor is probably thinking about frying pans and rakes.
If tits were wings it'd be flying around.