08-27-2007, 01:45 PM,
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fhyuan
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Uneven distribution-Al polyester coating
Hi, Gordon:
We have sprayed AlSi-polyester coating with acceptable porosity and HR15Y. However, the polyester was not considered to be evenly distributed.
The spray parameters as follows:
450 & 500A, 55 lpm Ar, 5.0 lpm H2, carrier gas Ar 3.0 lpm, stand-off 110-120 mm, surface speed 1000 & 1500 mm/s.
Regards,
fhyuan
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08-27-2007, 02:24 PM,
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Gordon
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RE: Uneven distribution-Al polyester coating
Hi Fhyuan
Is the uneven distribution ordered in any way (layering effect) or is it totally random?
Two possible causes for this effect:
1. Powder is a blend, so uneven distribution could start here, with settling or poor blending. This will tend to give a random variation in distribution in the coating. Thoroughly tumble powder before use.
2. During powder injection into the plasma, some powder classification effects occur. So you end up with concentration gradient across the plasma stream. This can show up in the coating as a layering effect, alternating layers of polyester rich and aluminum/silicon rich. To reduce this effect on the coating, changes to the way you handle gun and part motion and possible changing powder port orientation with respect to gun traverse direction (If powder port is pointing down, try rotating 45 or 90 degrees, which will change plane of powder classification) should help.
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08-27-2007, 03:42 PM,
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Gordon
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RE: Uneven distribution-Al polyester coating
Hi Fhyuan
I suspect you did not mean to open a new thread, so I've put your post below. Possibly, a little out of order as I was replying to the above when you posted this.
Quote:Uneven distribution-Al polyester coating
Hi, Gordon:
We have sprayed AlSi-polyester coating with acceptable porosity and HR15Y. However, the polyester was not considered to be evenly distributed.
The spray parameters as follows:
450 & 500A, 55 lpm Ar, 5.0 lpm H2, carrier gas Ar 3.0 lpm, stand-off 110-120 mm, surface speed 1000 & 1500 mm/s.
Is the primary Ar flow too high or the surface speed too large? By the way, the powder was internally fed behind the nozzle.
Regards,
fhyuan
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08-27-2007, 03:52 PM,
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Gordon
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RE: Uneven distribution-Al polyester coating
Hi Fhyuan
What equipment are you using?
Surface speed by itself is limited information. Rotating part - rotation frequency (RPM), part diameter and traverse speed or Static object - ladder scan, step distance, traverse/surface speed would be more useful.
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08-27-2007, 06:01 PM,
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Gordon
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RE: Uneven distribution-Al polyester coating
Hi Fhyuan
Where you can, rotate powder port 45 or 90 degrees and see if this improves things.
Try spraying the coating in much thinner layers per pass of the gun.
Check that your carrier gas flow is set correctly. You could try a few runs plus and minus a few points on the carrier gas flow to see if this has any effect.
Good luck and let us know how you get on.
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09-19-2007, 11:27 AM,
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Gordon
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RE: Uneven distribution-Al polyester coating
Hi Fhyuan
Quote:Yesterday, we sprayed two test pieces simultaneously. However, a puzzling result is that the microstructue of the coating are much different. More Al/Si phase is present in the coating on one specimen than that on the other one.
I find this a bit worrying, as it suggests that there are inconsistencies in your process or testing. I would try to find the cause of these differences, as it surely must put doubt in your mind as to the validity of previous work.
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09-24-2007, 02:40 PM,
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Gordon
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RE: Uneven distribution-Al polyester coating
Hi Fhyuan
I suppose you are seeing the natural variance within your sample. Sometimes you can take two cross-sections from the same test piece and find they look slightly different. A 2 dimensional view on a cross-section really is a very small view of the bulk structure. Try taking a few more sections from your previous samples and see if you are just seeing this normal variance.
It sounds like you are making good progress anyway, good luck
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09-29-2007, 03:57 PM,
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zhoudesign
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RE: Uneven distribution-Al polyester coating
The spray parameters as follows:
450 A, 70 lpm Ar, 8.0 lpm H2, carrier gas Ar 4.5 lpm, stand-off 110-120 mm,
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09-30-2007, 04:43 PM,
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fhyuan
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RE: Uneven distribution-Al polyester coating
zhoudesign Wrote:The spray parameters as follows:
450 A, 70 lpm Ar, 8.0 lpm H2, carrier gas Ar 4.5 lpm, stand-off 110-120 mm, Thank you Zhou.
We always have more polyester near the Al polyester/bond coat interface, even unacceptable poyester phase interconnection on the bondcoat, which is believed to cause the Al polyester coating susceptible to delamination in service. To some extent more Al(Si) phase is distributed away from the interface.
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12-29-2011, 08:30 AM,
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kriskros
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RE: Uneven distribution-Al polyester coating
(09-30-2007, 04:43 PM)fhyuan Wrote: zhoudesign Wrote:The spray parameters as follows:
450 A, 70 lpm Ar, 8.0 lpm H2, carrier gas Ar 4.5 lpm, stand-off 110-120 mm, Thank you Zhou.
We always have more polyester near the Al polyester/bond coat interface, even unacceptable poyester phase interconnection on the bondcoat, which is believed to cause the Al polyester coating susceptible to delamination in service. To some extent more Al(Si) phase is distributed away from the interface.
Hello All
From some time we get similar problem but with agglomerated aluminum particles. During spraying a lump of coating appears on gun nozzle and grow until in detach from nozzle and land on part. This local raise of material is pull out during turning and local loss of the coating appears as on attached photo. Any suggestions how can we avoid this lump grow on nozzle? We are using Metco 601NS powder.
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01-18-2012, 02:34 PM,
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kriskros
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RE: Uneven distribution-Al polyester coating
(12-29-2011, 08:30 AM)kriskros Wrote: (09-30-2007, 04:43 PM)fhyuan Wrote: zhoudesign Wrote:The spray parameters as follows:
450 A, 70 lpm Ar, 8.0 lpm H2, carrier gas Ar 4.5 lpm, stand-off 110-120 mm, Thank you Zhou.
We always have more polyester near the Al polyester/bond coat interface, even unacceptable poyester phase interconnection on the bondcoat, which is believed to cause the Al polyester coating susceptible to delamination in service. To some extent more Al(Si) phase is distributed away from the interface.
Hello All
From some time we get similar problem but with agglomerated aluminum particles. During spraying a lump of coating appears on gun nozzle and grow until in detach from nozzle and land on part. This local raise of material is pull out during turning and local loss of the coating appears as on attached photo. Any suggestions how can we avoid this lump grow on nozzle? We are using Metco 601NS powder.
Hello All
Maybe some advices in this matter ?
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01-18-2012, 07:19 PM,
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Gordon
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RE: Uneven distribution-Al polyester coating
Hi kriskros
What equipment and parameters are you using?
How long does it take for nozzle face or powder port to get fouled?
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01-20-2012, 01:33 PM,
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kriskros
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RE: Uneven distribution-Al polyester coating
(01-18-2012, 07:19 PM)Gordon Wrote: Hi kriskros
What equipment and parameters are you using?
How long does it take for nozzle face or powder port to get fouled?
Hello Gordon
We are using Sultzer 9MCE system with 3MBT gun. Primary 170SCFM argon; secondary 5,5SCFM hydrogen; amper 300; voltage 72; it takes about 20-30 passes to build this lump.
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01-21-2012, 06:57 PM,
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Gordon
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RE: Uneven distribution-Al polyester coating
Hi kriskros
Other than experimenting with parameters try:
Checking powder port alignment and that carrier gas flow and powder feed rate are constant and correct.
Have a careful look at your spraying set-up, can you modify the environment so that its less turbulent and with less dust flying around.
Polish nozzle face and powder port tips.
Set up routine strict regime for periodic shutdown to clean nozzle and powder ports from fouling.
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