[TheForge] Re: Powder Damascus

[Andrew Vida]

Mike Spencer wrote:

> I dunno.  The sintered widgets I've seen appear to be to some degree
> porous.  The sintered particles aren't totally fused, just, well,
> stuck very firmly together.  In this powder Damascus technique, the
> sintered billet gets rolled and forged to completely fuse the granular
> sarting material.

	Nah... the gears in your car's differential are almost certainly 
sintered, and those don't look very porous, do they?  The main 
difference between commerical sintering and so-called "powder damascus" 
is order of operations.  In commercial sintering, super high pressures 
are applied to powdered metal in a mold.  The pressures are so high that 
the pressed forms can be finish-machined.  From there they go into the 
sintering furnace and presto!

Powder damascus is sorta opposite... powder into a mold (retort), 
brought to heat, and then pressure is applied to stick the weld.

As for porous, that is for bronze bearings and the sort.  I believe that 
that is controlled by the amount of pressure applied and the precise 
configuration of the metal particles used. Voila!  Oilite!

	-Andy

PS: never ream the bore of an oilite bearing.  It closes the pores and 
the bearing loses all its attractive self lubricating properties.