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Nanotech Makes Steel 10x Stronger
An anonymous reader writes: A new metal-making process currently in testing at oil fields uses nano-scale plating to make metals like steel as much as ten times stronger than they would be without it. "[The process] uses an advanced form of electroplating, a process already used to make the chrome plating you might see on the engine and exhaust pipes of a motorcycle. Electroplating involves immersing a metal part in a chemical bath containing various metal ions, and then applying an electrical current to cause those ions to form a metal coating. The company uses a bath that contains more than one kind of metal ion and controls how ions are deposited by varying the electrical current. By changing the current at precise moments, it can create a layered structure, with each layer being several nanometers thick and of different composition. The final coating can be up to a centimeter thick and can greatly change the properties of the original material."
No details of achieved strengths - some maraging steels already Achieve >2GPa strength, and steel wires up to 5GPa, existing steel metallurgy already has methods for creating laminated structures and other high strength nanocomposites (eg look at bainite, pearlite, and other common steel morphologies with microscopic segregated grains of differing composition within the metal structure caused by methods of cooling). Bet anything these are at best only in about the 1-2GPa range - if they were genuinely better they would publish the numbers.
Electrochemical deposition is an incredibly expensive fabrication method, and yet the press release talks of using it in bridges? Some high strength (>1GPa) steels can be manufactured for around $1/kg. Without more concrete data these guys are touting snake oil.
Actually it does make sense small cracks do concentrate stresses at the head of the V which break through the crystal structure a layer at a time.
As a simple demo get a piece of paper and pull on it, you will find it pretty hard to tear it , now just nick the edge of the paper and try again, you should find it yields quite easily.
The tensile strength of steel would be a lot higher if it wasn't full of imperfections. incidentally there are two crystal structures you get with steel face centered cubic and body centered cubic
http://en.wikipedia.org/wiki/C...
now the interesting thing about this is that when you cool down steel rapidly you get one form and slowly you get the other form so if your quenching something more than a foot thick you get both types of crystals since heat just isn't removed fast enough from the centre. the larger crystal structure is in the centre and the smaller crystal structure is on the outside. This means the inside is trying to be bigger than the outside. so the outer surfaces are massively stressed. like a bomb stressed seriously. You can't cut through steel stressed like this with a saw as the cutting would unbalance the stresses and it would blow apart, so you have to do something called plunge grinding which is done in a massive lathe with a grinding wheel taking it down equally on all sides.
This is what happens when you produce a roll for a cold rolling mill the outside is very hard with a softer core. Usually the forces are lower than the uts of the steel but sometimes it isn't and you get catastrophic failures. generally this happens in the quenching tank where its safe you normally hear a few bangs as lumps of steel spawl off from the outside followed by a boom as the roll breaks apart and goes crashing down to the bottom of the tank.
Rarely they fail after the heat treatment, joe the hardness tester where i used to work was nearly killed by one. he'd hardness tested it around 12pm (the hardness was abnormally high around 890 vickers) an hour later it blew apart a ton and a half of journal end was launched across the factory floor missing his legs by inches. he was off work for a week after with the shock. We also had a used roll blow up in a storage warehouse one weekend and it took a wall out, this had been in service and had been worn down to below a serviceable size. Even after all that time it was still stressed ...
back on topic , it seems reasonable that by removing the sites for cracks to occur the uts of the steel will be much higher, normally the way round the problem is to make the thing bigger that way the forces applied will not break the cross section of course that makes it heavier and harder to work with which is why its a specialized area like drilling where this has been applied, with the plating thicknesses used the cost will be way higher than for the regular steel pipes, i'd expect probably more than 10x the cost but the rig would be able to drill deeper and that's what matters, and the return on that makes the drilling costs look like peanuts.
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As a corrosion coatings engineer, I can tell you that this already happens. It's the whole reason I have a job. You see those green pipes going down the road on a flatbed truck? That's fusion bonded epoxy (powder coating) on plain jane steel pipes. There are several places that FBE coat their rebar before putting it in concrete structures, like you suggested. Combine a good corrosion coating with some healthy cathodic protection, and you can tremendously increase the lifespan of your infrastructure.
However, there are a lot of snake oil salesmen that try to claim "nano" coatings, when really their just dipping the steel in silane or electroplating it or any number of things that look fancy. They probably do help corrosion, but they are no more "nano" than bailing wire and bubble gum. Unfortunately for them, I'm friends with a PhD in advanced material sciences, and it's pretty easy for her to sift through the BS.