Spray on a small hole

[Spark]

hi,
Recently, I’m doing a trial for spraying metco 68 Fns(T800) coating on the ID surface of a small hole.
I use metco system F4MB gun, the part's ID is 14mm, with height 10mm.
The parameter I use is the same as we spray normal, Just attack angle change to 60 deg.

After the micrographic test, the hardness of the coating is lower than normal, also high porosity companied.
Is anybody who has the experience for spraying on a small diameter?

I guess the flame has cover almost the entire surface during it rotating, and some of the area’s attack angle is too bad that why the porosity is too high.

Also I got a question about such kind of small diameter part, if I want do micrographic test, I can cut the part directly, but if I want do bond test, what should I do? The test coupon is large than the part, and the geometry are not the same, so I doubt the bond test result.

BR

[Spark]

(07-10-2014 03:03 PM)Spark Wrote:  hi,
Recently, I’m doing a trial for spraying metco 68 Fns(T800) coating on the ID surface of a small hole.
I use metco system F4MB gun, the part's ID is 14mm, with height 10mm.
The parameter I use is the same as we spray normal, Just attack angle change to 60 deg.

After the micrographic test, the hardness of the coating is lower than normal, also high porosity companied.
Is anybody who has the experience for spraying on a small diameter?

I guess the flame has cover almost the entire surface during it rotating, and some of the area’s attack angle is too bad that why the porosity is too high.

Also I got a question about such kind of small diameter part, if I want do micrographic test, I can cut the part directly, but if I want do bond test, what should I do? The test coupon is large than the part, and the geometry are not the same, so I doubt the bond test result.

BR

nobody can help me?any suggestions?

[JustSprayGuy]

[/quote]

nobody can help me?any suggestions?
[/quote]

Unfortunately, that's just a limitation of spraying. You can't spray at such extreme angles and expect the same coating quality that you would get spraying head on. I don't know if it's a technical term or just one we use around the shop but we call it shingling of the coating. When spraying at that angle the spray particles start to adhere to the surface in a shingle like manner which negatively effects the coating characteristics. I doubt there is an ID attachment for the f4 gun designed to spray such a small diameter. If at all possible try lessening the angle at which your spraying is the only advice I can offer.