On 24/04/13 19:26, Ed Huntress wrote:
On Wed, 24 Apr 2013 19:09:50 +0100, David Billington
wrote:

On 24/04/13 18:16, Ed Huntress wrote:
On Wed, 24 Apr 2013 17:48:52 +0100, David Billington
wrote:

What you're describing is by far the most common way it's done.

PM can be fascinating. By mixing powders and sintering at full
diffusion temperatures, you can produce alloys that are not possible
any other way.

For example, the most exotic of the high-speed-steels: Crucible CPM
REX 121. You can't make it by melting. That stuff is HIPped, BTW.

Regarding memory, I can empathize with that. d8-)

I have a book called "The Component Contribution Engine Progress Through
the Specialist Manufacturers" by Alan Baker ISBN 0 09 136290 3 and it
mentions the use of what they call powder forging being used by GKN to
produce conrods for the Porsche 928. The book dates from 1979 and the
928 1978 so looks like some high performance applications have been
around for a while.
Yes, I remember that. The 928 engine used a lot of advanced
technologies. Porsche was trying all their new tricks, including
running the pistons in aluminum cylinders. Unlike the Chevy Vega, they
got it right.
I mentioned the Vega engine to a mate that works in engine development
and he found it hard to believe they went all that trouble developing
the block process then put an iron head on it to save money but then
maybe that was GMs way. I do remember back in the 70s the engine had a
bad reputation.
There were several basic engineering screw-ups, some so obvious that
it was hard to believe.

You may remember the Cosworth version of the Vega, which had an
aluminum, dual-cam Cosworth head on the same engine block. Some car
enthusiast wrote a letter to one of the two big US sports-car
magazines -- Sports Car Graphic or Road & Track -- and asked how you
could tell a regular Vega from a Cosworth Vega. There was no obvious
Cosworth insignia on the car; just one little badge somewhere.

"Look under the car," said the magazine editor. "If there's a puddle
of oil under it, it's a regular Vega." d8-)
Yes I was aware of a Cosworth version, maybe the wheels give it away as
well. The oil leak maybe like the old joke about British bikes, it's not
leaking oil just marking its territory!.


They may have sleeved the 928 later, but it started as a hypereutectic
aluminum block with the pistons running directly in the block.
IIRC one of the Mercedes Benz engines is the same, a V8 I think
/
/
I presume this would be an application of what
you're referring to as HIPed. IIRC the hot initially powder form is
placed in dies and struck to produce a 100% part with high dimensional
and weight accuracy compared to standard forging processes.
I doubt if they were HIPped. I saw Chevy con rods made of PM in the
mid-'90s, and they were being made with conventional sintering and
then post-pressing to increase the density.
I looked up what HIP was and I think you're right that wasn't what was
used rather heating to a high temp and striking the powder pressing to
consolidate the material. I noticed a youtube video on HIP so will watch
that shortly.

BTW the book is a fascinating read if you haven't read it already and it
looks like it's available cheaply on Amazon. Maybe a little dated in the
last 34 years but still a good read.