Bill, why do you say the EF process "isn't suited for out flat side plate needs"? And what do
you

mean when you say that "Almost any aluminum hardfacing system can have flaking problems.".

and "I was

told the area where the transition is made is crucial" Are you refering to a spray on hard

surfacing

process, such as det gun, or plasma spray? and Meaning that a flange or other raised portion

is what

is crucial?

Royce

Royce, The Electrofusion process used by Kawasaki is done by heating the raw surfaced but
otherwise finished barrel to "a specific temperature" then a wire of the desired plating materials
is placed in the cylinder. (I believe tungsten was typical) A HUGE current and voltage is applied
to the wire causing it to literally explode. The atmosphere in the application chamber, (either
oxygen or vacuum or other gas), then controls the final product applied to the walls. As explained
to me the prep of the aluminum surface is very important. When anything is applied to aluminum
controlling oxides is difficult. The EF process blasted the coating material into the surface
creating a great bond. The reason I believe the process is not used on plate surfaces is waste and
uniformity. You can explode the wire above a flat surface but the area closest to the wire gets
the heaviest coating. Often several applications are needed to build up a thick enough coating. A
bore is obviously the best setup for this process. I am trying to find out if the Mazda material
can be plasma sprayed or sputtered on. Paul mentioned the problem with coating aluminum, as it
starts getting soft at fairly low temps. Nowhere near melting of course but softening. This
surface change makes it possible for the coating to work loose. The other problem is that the
coatings we normally apply, normally have a vastly different coefficient of linear expansion than
the base aluminum. This is the crucial area I mentioned earlier. Anodize is an example of this.
The aluminum oxide expands less quickly than the aluminum it is generated from. In the case of
ceramic coatings like plasma spraying the difference is pronounced. The CLE for aluminum is 10
to-5 units per deg F. For ceramics it can be ten times higher. This causes surface stress on every
thermal cycle. If the bond to the surface is strong enough...no problem. If not then cracking and
flaking. This problem is on every coated surface. Corners or raised flanges just make things more
difficult since a corner can concentrate stresses. Bill Jepson

Gottcha Bill, yep that process would certainly not work very well on a flat plate for sure.

Hopefully the aluminum housings will not get that hot.  Paul mentioned a 250 degree number, don't know
where he got that from, but it sounds reasonable. Racing Beat has had no problems with their housings,
and they are plasma sprayed.
Royce

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