Posted by ALex (188.8.131.52) on 17:06:04 05/04/06
In Reply to: Re: T800 Coating Thickness limit by HVOF posted by Gordon England
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.
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