Posted by ALex (202.156.6.69) on 17:06:04 05/04/06
In Reply to: Re: T800 Coating Thickness limit by HVOF posted by Gordon England
Gordon,
I am spraying the flange surface flange which is showing up. The
liner is clamped onto a turn table. i tilt the table to an angle
where the gun spraying angle reaches circa 80-90 deg.
Pertaining reducing thickness of coating is not possible. 0.025" is
the limit which can not be exceeded as a conformance to the manual.
Very much depend on the incoming part condition whether build up is
required or not.
T800 coating seldom has chipping problem if single top coat is
required. Vice versa, it happens very frequently when T800 is
sprayed on top of a Inco718 as build up bpnd coat.
as for the edges, we have more than 30 edges as the liner has many
slots that form lowered down steps on the flange surface. Thus at
both sides of the slots (Steps) that is where chippings
occured. We use hard masking to cover the lowered steps. I am not
sure whether yoju could imagine, but generally what i m trying to
say is we will have no escape but to spray on all the edges as part
is rotating.
After coating the coating need to be machined and edges to be grind
to angular steps like : IIIIIIII_____IIIIIIII. where I is the build
up. and ____ is the slots or step down.
I will tried out some of your recommendation esp on the elimination
or reduction of stop time as most of the time the part temperature
right oafter the spraying (5 passes) is still below 80deg
as the part is quite big. heat transfered to large surface area and
disseminate to all the part. I will try something like maybe
10passes..and check the part temp.
Gun traverse is not a problem i think as the flange is about 0.5 "
in width and circular.gun travel from ID to OD to and fro as the
surface rotate in clock wise motion. the deposition is even at all
points.
I will continue monitor the process and post any update i observe
or outcome of my experiment.
Thanks
Cordially,
Alex Chan
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