Re: tungsten carbide properties

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>" <Hollmike-at-aol-dot-com>

In a message dated 8/11/01 7:06:58 PM Pacific Daylight Time, tesla-at-pupman-dot-com 
writes: 


>
> I wonder if copper sulfate and electricity could plate them with copper so 
> they could be easily soldered.  With water cooling, the solder would not 
> melt.  Maybe Mike H. knows :-) 



Yes, it can.  I just finished a test on copper plating a tungsten carbide 
mill bit and it plates very easily. Tungsten is also easily plated.  I just 
plated a welding rod too.   
  There is something to keep in mind if you intend to plate these with 
copper, or any metal more noble than copper(silver, gold, eg).  The redox 
potential is sufficiently high enough to cause spontaneous plating.  In other 
words, the copper will start depositing itself onto the tungsten without the 
need of a voltage applied.  This will, of course be a problem as the 
interface between the two metals will have a salt layer which will prevent 
the copper from adhering to the tungsten.  This is easily solved though.   I 
simply applied the voltage to the copper anode and the WC cathode before 
lowering the WC cathode into the plating bath.  This allows the copper to 
begin plating instantly without causing the oxidation of the tungsten.   
  I would suggest a plating bath that contains approximately 30 g/L 
copper(copper sulfate pentahydrate is about 25% copper by weight so 120 g/L 
of the salt) and about 50g/L sulfuric acid.  These are by no means critical, 
but will make a nice plating solution.  In my tests this morning, I did not 
even measure out anything.  I basically saturated the solution with copper 
sulfate and added the acid -causing some of the copper sulfate salt to 
crystallize out.   
  One other thing I would strongly suggest is that you use a power source 
that is adjustable.  I would apply a voltage low enough to insure that NO 
hydrogen bubbles evolve from the tungsten cathode.  Aside from the obvious 
danger of igniting the hydrogen(wouldn't really worry about this though), if 
the bubbles are forming at the cathode, the deposit will be very poor.  This 
is because the current density is too high and the result will be a powdery 
deposit of copper which will fall right off.  I experienced this when plating 
the welding rod because it has little surface area compared to the mill bit.   
One other concern about generating gas bubbles at either the anode or 
cathode(oxygen will form at the anode if the voltage is too high) is that the 
bubbles burst at the surface of the liquid causing a sulfuric acid mist in 
the air.  This is very bad to breathe and will also wind up splattering all 
over everything. 
Mike