On Aug 19, 11:50*am, wrote:
On Aug 19, 9:04*am, tnik wrote:





On 8/19/2010 8:51 AM, wrote:

On Aug 18, 2:43 pm, *wrote:
OK guys.. Hopefully someone can help me out here..

We have these 4140 plates for a customer. On the print they call out for
.007 - .009 thick chrome on one face finished. So we try to get the
plater to put .004-.005 over so we can grind them flat. We tried having
them only putting .001-.002 over, but that never worked out well.
The plater we use is having a really hard time getting a consistent
buildup all over the plates.. And recently we are seeing a crap load of
bubbles, and some of the plates are actually flaking on the edges. So,
here is two questions to the more knowledgeable than I.

1) Is there any other type of coating that is comparable or better than
chrome, that we could suggest to our customer, that would save the time
and anguish of us grinding, finding out the chrome is bad, and sending
the plates back to get more added?

2) If it's the chrome plater that is actually at fault, does anyone know
of a good plater that is in Florida, preferably near central, but not
required.. We can UPS the plates. I'll even send them out of state if
need be.. Anything is better than the situation that we are in now.

Sounds like bad design. *Electroplating will be hard to get even
coating at that thickness, field strength at corners causes extra
build up. *It's waaay too thick, like the other poster said, hard
chrome is used in THIN applications. *If the customer needs a hard
face, how about one of the flame-sprayed coatings, or TiN? *Bubbles in
plating is a process control problem and chrome doesn't stick very
well to steel without an intermediate layer or two, usually copper and
nickel. *Electroless nickel would stick well, if it's just a
decorative thing. *It all comes down to what the hard chrome is
supposed to do.

Stan

The chrome is there for wearing against wood in a big mulcher. I've
talked to a couple of people today, and with your guys suggestions I
have a small arsenal that I can go to the customer and try to do
something different.- Hide quoted text -

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Hardening the 4140 isn't enough? *Wear plates should be readily
changeable, anyway. *Might be a more abrasion resistant alloy would
work better(and cheaper). *Plating these days isn't cheap.

Stan- Hide quoted text -

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Just thought of another thing, with regard to bubbles. Are these
plates getting any sort of post-process heat treatment to remove
hydrogen? If not, that's a BIG problem. Look up "hydrogen
embrittlement". The thicker the plating, the more problems you get
with it, too. All those freed protons in the plating bath go
somewhere and mostly right into the workpiece.

Stan