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Re: Tungsten vs. Tungsten

Tesla List wrote:
> 
> >From richard.craven-at-mkbbs.co.uk Thu Nov 28 20:39:15 1996
> Date: Wed, 27 Nov 96 20:11 +0000
> From: richard.craven-at-mkbbs.co.uk
> To: TESLA-at-pupman-dot-com
> Subject: Re: Tungsten vs. Tungsten
> 
> Daryl and everyone
> 
> [Daryl said:
> 
>    I spent several hours today playing around with my arc lamp
>    power supply and some tungsten rod and a tungsten carbide lathe
>    insert to see which faired better in a torture test.]
> 
> Thanks for taking the trouble to look into the idea of using tungsten
> carbide. As we can see, it is not an insulator, but different grades
> have differing conductivities. A piece that I measured at work using a
> DVM was short circuit ( it was an uncoated tooling bit about half an
> inch long by 1/4 inch thick, lozenge shaped).
> 
> [From Brent:
> 
>    Used the round disks that I silver-brazed onto brass
>    studs. In all honesty, they ablated (wore) away very quickly. I had
>    used 3/8" round tips. I now use 3/16" pure tungsten rod, which is
>    smaller, and ablates a bit more slowly. From what I understand, if
>    you can cool the electrodes down a bit, they last longer. I plan to
>    put a high-velocity blower nozzle on my gap to cool things down.]
> 
> My intention is to use tungsten carbide rods, 5mm diameter by 10mm long,
> inserted into my s-s electrodes. The electrodes on the disk will be
> cooled by virtue of 3000rpm speed, and the 4 stator electrodes are sunk
> in turn by large aluminium blocks (2 inch tall by 2 inch diameter
> cylindrical blocks). Air could be blown at the gap channels but I hope
> not to need to do this.
> 
> My interest in using tungsten carbide is because it is more available
> for me than the tig welding electrodes. I expect them to be a viable
> alternative as long as their conductivity is checked. I am having my
> rods made by a local company. The cost works out the same as buying
> machine inserts. The material is usually tungsten carbide and ditungsten
> carbide ( made by heating metallic tungsten with a small amount of
> cobalt as a catalyst) which is sintered at a low temp (900 deg C) and
> then machined. It is then high temperature sintered (1300 deg C) at
> pressures of several tens of kg per mm sq. Cobalt  is added here as well
> to help with the sintering. Co dissolves 30 or 40 per cent by weight of
> W and thus helps the mixing and sintering process. Other matls can be
> added (ceramic fillers) which will account for differing conductivities.
> I will be using the rods end on probably. If I go for disks or other
> shapes, edgeways on as RWS suggests is an excellent idea.
> 
> Richard Craven, Malvern, England
> ---
>  CMPQwk #1.42 UNREGISTERED EVALUATION COPY


Richard -

  What kind of costs are you looking at for the Tung-carb rods? I'd be
tempted to try a couple in my gap to see what happens.

- brent