New Here

[DQW]

I'm new here, so I thought I'll say 'Hi'.

 

I hope to clear up misconceptions and answers questions in physics, materials science/engg and physical/theoretical/quantum chemistry.

[5614]

Hey

 

Sounds like you're a cool person to have around, so welcome!

[Ophiolite]

Welcome DQW. Does your materials science knowledge embrace fracture properties of tungsten carbide, by any chance?

[blike]

Welcome!

[DQW]

Thanks 5614, blike and ophio !

 

Ophio, as far as pure WC is concerned, everything I know about it will likely fit inside a single page. Of cource I can draw extrapolations from the general mechanical behavior of carbides and similar ceramics with low fracture toughness, but if you want to know whether I have done anything specific with WC, here's my answer.

 

I have looked a little bit into HVOF spray coatings using WC/Co. These are very popular in the aeronautical (and tooling) industry, for their exceptional wear resistance. Embedding the WC particles in a Co matrix (we are talking about a cermet here) greatly improves the fracture toughness (and ductility). In fact, I don't know that pure WC gets used for very much.

 

I have also recently heard something about improving the fracture toughness by making the material nanocrystalline. But I really just came across this once, some time ago, and never followed up, so I'm not even sure if it is done only for WC/Co or even for plain WC. You could try Gooling it, unless of course, this is all old hat to you. I shall too, when I find the time.

 

In any case, if you have a specific question, go ahead and post away. I most likely wouldn't be much help, but there's nothing lost in asking, is there ? Besides, there's might be several members that are experts in carbides, tooling or such.

[JohnB]

Welcome.

as far as pure WC is concerned, everything I know about it will likely fit inside a single page.

A beginner huh? I can fit everything I know about at least 4 different sciences on one page.

[coquina]

I'll join in the welcome. I own a machine shop, & among other things, we make parts (usually one-offs) in support of experiments at Jefferson Lab's accelerator, and often have to machine unusual materials. I'll probably be calling on your expertise from time to time.

[DQW]

Thanks JonB and coquina.

 

I'll join in the welcome. I own a machine shop, & among other things, we make parts (usually one-offs) in support of experiments at Jefferson Lab's accelerator, and often have to machine unusual materials.

Ah, so you're in Newport News or thereabouts ?

 

I'll probably be calling on your expertise from time to time.

"Expertise" ? You flatter me ! But your good looks and sweet words will not win me over . Besides, I really haven't very much experience machining any unusual materials. And you know how far theoretical knowledge goes when it comes to machining ! You don't know it until you do it, and you don't believe anyone who tells you it won't work, unless they've tried it first (and even then, you're skeptical).

 

What kind of unusual materials do you machine for the folks at JLAB ? I would imagine most of their metal is 304 Stainless. Well, actually, when I think about it, there's a few others that come to mind - beryllium windows for x-rays, possibly cadmium or zirconium rods, molybdenum targets, etc.

[YT2095]

I`ve seen you `round the forums, not had chance to say Hi formaly, Welcome dude

[DQW]

Thanks YT !

 

I just noticed that there's a separate thread meant specifically for introductions, which is where I should have introduced myself. I apologize for the omission.

[Phi for All]

Your obvious knowledge and the fact that your thread didn't start out, "hey ppl, n00b here!" earned you a reprieve on the introductory thread.

 

Welcome and enjoy.

[DQW]

Thanks for the welcome, Phi.

 

Does my mass increase with my post-count ?

[Phi for All]

Does my mass increase with my post-count ?

Indeed. Except posts in General Discussion aren't included in post counts.

[coquina]

Thanks JonB and coquina.

 

Ah' date=' so you're in Newport News or thereabouts ?

 

"Expertise" ? You flatter me ! But your good looks and sweet words will not win me over . Besides, I really haven't very much experience machining any unusual materials. And you know how far theoretical knowledge goes when it comes to machining ! You don't know it until you do it, and you don't believe anyone who tells you it won't work, unless they've tried it first (and even then, you're skeptical).

 

What kind of unusual materials do you machine for the folks at JLAB ? I would imagine most of their metal is 304 Stainless. Well, actually, when I think about it, there's a few others that come to mind - beryllium windows for x-rays, possibly cadmium or zirconium rods, molybdenum targets, etc.[/quote']

 

I'm in York County - about 10 miles away from Jlab. The last unusual material, which wasn't directly for JLab, but which ended up there, was a super magnet. The company which was doing the experiment forgot to order one with a hole in it. You probably know those magnets are sintered, so they shouldn't be so difficult to cut - had we been able to get the chips out of the hole! I had never seen a "super magnet" before - you could not pick it up from magnetic material, I don't know how much strength it would take to make one release its hold on an iron table, but one of my employees who is a weight lifter, could not budge it. We had to slide it onto a piece of plastic.

 

Anyway - when we tried to drill the hole the chips adhered to the inside of the hole as though the material had never been drilled. We asked the fellow how much it would cost to reorder the magnet with the hole, and based on the price, told him it would be more cost effective to do that. I'm sure we could have figured out something eventually, but not for $40 or $50.

 

We use 17-4 as the main material for machines we build which repair high pressure steam valves in-line on nuclear vessels. It cuts reasonably well and does not change significantly after heat treating - therefore, you don't have to grind it.

 

Another neat job we did was "pinger housings". Do you remember hearing that dolpins were used to find mines in the Red Sea? We built the metallic portion of the parts that trained them. The explosives were removed and parts that emitted a particular "ping" were substituted. The dolphins were trained to find them by the noise they emitted and then trained to recognisz the mines on sight.

 

We also machine a large variety of machinable plastics. They are a clear thrill because the size changes substantially with temperature. Right now I am making parts that go in the shore power connection of submarines to seal the electrics from seawater when the sub is submerged.

 

In what technologies does you lab specialize?

[DQW]

I'm in York County - about 10 miles away from Jlab. The last unusual material, which wasn't directly for JLab, but which ended up there, was a super magnet. The company which was doing the experiment forgot to order one with a hole in it. You probably know those magnets are sintered, so they shouldn't be so difficult to cut - had we been able to get the chips out of the hole! I had never seen a "super magnet" before - you could not pick it up from magnetic material, I don't know how much strength it would take to make one release its hold on an iron table, but one of my employees who is a weight lifter, could not budge it. We had to slide it onto a piece of plastic.

I've seen a picture of a car hanging of such a permanent magnet (no, it was not an electromagnet).

 

Anyway - when we tried to drill the hole the chips adhered to the inside of the hole as though the material had never been drilled.

Wow, that's interesting ! I wouldn't have thought that these would have been really hard to remove. These magnets are usually magnetized in the direction of the thickness (not along the length or width/dia - in which case it would be impossible to remove the chips).

 

but I We asked the fellow how much it would cost to reorder the magnet with the hole, and based on the price, told him it would be more cost effective to do that. I'm sure we could have figured out something eventually, but not for $40 or $50.

How big was this magnet ? I'd be willing go bet a smallish sum that this was a sintered NdFeB magnet. Those things are quite brittle. The first thing you are warned about, when handling NdFeB magnets is to be very careful when you are near metal or when handling two or more magnets. They accelerate (if released) rapidly towards anything iron or steel and strike it hard and shatter into tiny pieces. But this is more true of the smaller sized magnets.

 

I'm surprised you were able to drill it easily - they're almost like ceramics, in terms of machinability. Are you sure it didn't have some kind of epoxy-based binder ? Those are called bonded NdFeB magnets, and are much easier to machine than the pure, sintered kind. But the sintered magnets are stronger (magnetically).

 

Did you have to use diamond bits ? I'm sure you were warned to used lots of coolant (the magnet will demagnetize at about 250F), and to be prepared to handle a fire. The chips are extremely flammable (like magnesium powder). If they get too hot, they will auto-combust and burn with a bright, hot flame making all kinds of toxic gases.

 

We use 17-4 as the main material for machines we build which repair high pressure steam valves in-line on nuclear vessels. It cuts reasonably well and does not change significantly after heat treating - therefore, you don't have to grind it.

17-4 for high yield strengths I guess. I was imagining a lot of high-vacuum parts for the accelerator, for which you would need non-magnetic steels. The austenitic steels (like 304) are much better in this respect, than the martensitic steels (like 17-4PH).

 

Another neat job we did was "pinger housings". Do you remember hearing that dolpins were used to find mines in the Red Sea? We built the metallic portion of the parts that trained them. The explosives were removed and parts that emitted a particular "ping" were substituted. The dolphins were trained to find them by the noise they emitted and then trained to recognisz the mines on sight.

That is neat ! I remember the news about the dolphins - I thought it was in the Mediterranean, but I must be mistaken.

 

We also machine a large variety of machinable plastics. They are a clear thrill because the size changes substantially with temperature.

I found this extremely bothersome when I wanted to machine some teflon in a hurry and had a tolerance of 1 mil on diameters. It took several steps as I got close because of thermal variations. And if you let the teflon get too hot, it (i) warps and (ii) makes nasty carcinogenic vapors, so I had to be slow and patient with it, when I wasn't feeling like either. Polypropylene and polyethylene are fun to machine. Acrylic is okay too, as long as you go slow. The nastiest in the plastics category (composites actually), in my tiny experience, is fiberglass - not that it's hard to machine really, but it just wears down your tools real fast.

 

Right now I am making parts that go in the shore power connection of submarines to seal the electrics from seawater when the sub is submerged.

Are you at liberty to say what material is used ? There are now dozens of specialized seawater resistant steels and other alloys. I was surprised to find that titanium is excellent (but expensive, of course) for marine applications. And although titanium isn't terrible machining (or welding) friendly, it isn't too bad either.

 

In what technologies does you lab specialize?

Right now, I'm part of a pure physics lab - we do not produce any technology (though we build a lot of stuff for our experiments); we do research in fundamental quantum mechanical phenomena in 2-dimensional systems in the solid state.

 

About 5 years ago, I spent a fair bit of over a year, synthesizing and characterizing high strength permanent magnets, very much like the one you had to drill.

[coquina]

How big was this magnet ? I'd be willing go bet a smallish sum that this was a sintered NdFeB magnet. Those things are quite brittle. The first thing you are warned about, when handling NdFeB magnets is to be very careful when you are near metal or when handling two or more magnets. They accelerate (if released) rapidly towards anything iron or steel and strike it hard and shatter into tiny pieces. But this is more true of the smaller sized magnets.

You'd be betting right. We used a carbide drill. As I said - I just told the people I'd make the effort - when it wasn't going to be an easily accomplished task, I quit and told him to buy a replacement.

 

I was imagining a lot of high-vacuum parts for the accelerator, for which you would need non-magnetic steels. The austenitic steels (like 304) are much better in this respect, than the martensitic steels (like 17-4PH).

Yes, most parts for the accelerator non magnetic stainless, often 304. You probably know 304 is ornery to cut also. They are often purchased parts from companies such as MDC http://www.mdc-vacuum.com/urd/uniface.urd/ecf0018w.display which we modify. One thing we have to be careful about is keeping a sharp cutting edge on the tools, and keeping plenty of coolant on the parts. If heat builds up, the material work-hardens, then you really have a mess. We use a lot of disposable tipped carbide tooling.

 

What happens chemically when a material work-hardens, anyway?

 

That is neat ! I remember the news about the dolphins - I thought it was in the Mediterranean, but I must be mistaken.

 

They're used all over, wherever there is danger of mines. There was coverage of them being used - probably Persian Gulf rather than Red Sea - prior to invasion of Iraq.

 

The nastiest in the plastics category (composites actually), in my tiny experience, is fiberglass - not that it's hard to machine really, but it just wears down your tools real fast.

 

We machine a fair amount of G10. Thank God for throw-away inserts. The abrasiveness of it will ruin the accuracy of your machine tool too. We can divert our coolant tank to spray with a garden hose and nozzle. We keep flushing the chips out of the machine frequently, the big pieces get caught by the chip conveyor, the tiny pieces get caught by a Racor filter.

 

Are you at liberty to say what material is used ?

A "special" kind of polyurethane. It flexes and seals against the boat-side plug.

 

BTW - I was aboard a nuke sub a couple of years ago to check out feasibility of using one of the portable machines we build to cut out a through-hull sleeve. It was very interesting ... and very compact. The officer who was escourting us said that if you tie a rope tight from one side of the other when the boat is on the surface, it will have 8" of slack when the boat is at depth. The hull compresses that much.

 

Interesting discussion, but I gotta go to work. Catch you later.