Best place to mesure coating temperature
07-31-2020, 10:22 PM,
#1
Best place to mesure coating temperature
Dear all, hope you are all doing fine.

Where do you recommend me to measure the coating temperature, based on the image attached?

Best regards


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08-01-2020, 07:03 AM, (This post was last modified: 08-01-2020, 07:34 AM by Vadim Verlotski.)
#2
RE: Best place to mesure coating temperature
(07-31-2020, 10:22 PM)vcduramais Wrote: Dear all, hope you are all doing fine.

Where do you recommend me to measure the coating temperature, based on the image attached?

Best regards


Hi
only the temperature in point A is decisive for the coating process: that is the substrate temperature before coating. By adjusting the temperature in point A, you can influence tension stresses in the finished coating. Temperatures in all other points are temporary and do not provide valuable information.
By the way, the temperature at point C is not at all the temperature of the coating, but the temperature of the particles at the moment of their connection with the substrate, the so-called temperature of the spraying spot. Of course, the temperature of the spraying spot is also very important for the spraying process, but it is not determined by the coating formation process, but by the powder material and its speed. It goes without saying that the temperature at point C is very different for different methods of spraying and sprayed materials.

Regards
Vadim
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08-03-2020, 02:46 AM,
#3
RE: Best place to mesure coating temperature
(08-01-2020, 07:03 AM)Vadim Verlotski Wrote:
(07-31-2020, 10:22 PM)vcduramais Wrote: Dear all, hope you are all doing fine.

Where do you recommend me to measure the coating temperature, based on the image attached?

Best regards


Hi
only the temperature in point A is decisive for the coating process: that is the substrate temperature before coating. By adjusting the temperature in point A, you can influence tension stresses in the finished coating. Temperatures in all other points are temporary and do not provide valuable information.
By the way, the temperature at point C is not at all the temperature of the coating, but the temperature of the particles at the moment of their connection with the substrate, the so-called temperature of the spraying spot. Of course, the temperature of the spraying spot is also very important for the spraying process, but it is not determined by the coating formation process, but by the powder material and its speed. It goes without saying that the temperature at point C is very different for different methods of spraying and sprayed materials.

Regards
Vadim

Thank you very much!
Reply
08-03-2020, 01:42 PM,
#4
RE: Best place to mesure coating temperature
(08-01-2020, 07:03 AM)Vadim Verlotski Wrote:
(07-31-2020, 10:22 PM)vcduramais Wrote: Dear all, hope you are all doing fine.

Where do you recommend me to measure the coating temperature, based on the image attached?

Best regards


Hi
only the temperature in point A is decisive for the coating process: that is the substrate temperature before coating. By adjusting the temperature in point A, you can influence tension stresses in the finished coating. Temperatures in all other points are temporary and do not provide valuable information.
By the way, the temperature at point C is not at all the temperature of the coating, but the temperature of the particles at the moment of their connection with the substrate, the so-called temperature of the spraying spot. Of course, the temperature of the spraying spot is also very important for the spraying process, but it is not determined by the coating formation process, but by the powder material and its speed. It goes without saying that the temperature at point C is very different for different methods of spraying and sprayed materials.

Regards
Vadim

Dear Vadim

The reason for this question is that when I was using fine powders (<22 microns) I had cracking problems even when coating with substrate temperature about 100-200°C.

I have a air cooled GTV gun and was using 86 10 4 Metco powder with fabricant parameters, 0,005 mm thickness per pass and 0,4 final thickness.

I'm acquiring a new water cooled MEC 2700 gun hoping to get better and no cracking coatings.

Do you have any advice for me when using fine powders with the new MEC 2700 gun (7 bar combustion pressure)?

Best regards.

Vitor
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08-03-2020, 04:19 PM, (This post was last modified: 08-03-2020, 04:24 PM by Vadim Verlotski.)
#5
RE: Best place to mesure coating temperature
Dear Vitor,
simply said, air-cooled GTV burners produce hot and slow particles and water-cooled MEC 2700 burners make the particles less hot but faster. The MEC 2700 burner is definitely advantageous for the commercial powder WC86Co10Cr4 < 22 microns, because this powder needs more speed than temperature. You will see that, as well at the layer quality and also at the crack formation.

Although it is possible to produce the WCCoCr-coating without cracks with the GTV burner (you need a very thin layer per pass, <5 micron), it is easier with MEC burners, since it is not necessary to have an extremely thin layer per pass.

In order to get an optimal layer quality, you should not only adjust the burner parameters as well as the spraying distance (spraying distance for faster burners is generally higher s for slow ones).

Regards
Vadim
Reply
08-03-2020, 05:20 PM,
#6
RE: Best place to mesure coating temperature
(08-03-2020, 04:19 PM)Vadim Verlotski Wrote: Dear Vitor,
simply said, air-cooled GTV burners produce hot and slow particles and water-cooled MEC 2700 burners make the particles less hot but faster. The MEC 2700 burner is definitely advantageous for the commercial powder WC86Co10Cr4 < 22 microns, because this powder needs more speed than temperature. You will see that, as well at the layer quality and also at the crack formation.

Although it is possible to produce the WCCoCr-coating without cracks with the GTV burner (you need a very thin layer per pass, <5 micron), it is easier with MEC burners, since it is not necessary to have an extremely thin layer per pass.

In order to get an optimal layer quality, you should not only adjust the burner parameters as well as the spraying distance (spraying distance for faster burners is generally higher s for slow ones).

Regards
Vadim

Dearl Vadim

Thank you for helping.

Right now I use 180-200 mm and I think with the new gun it's going to be something about 260 mm, correct?

There is any relation betwen the maximum layer thickness and the particle size? We often do coatings with +0,8mm of thikness and I hope this does not cause me future problems.

Best regards

Vitor
Reply
08-03-2020, 06:02 PM, (This post was last modified: 08-03-2020, 06:09 PM by Vadim Verlotski.)
#7
RE: Best place to mesure coating temperature
Dear Vitor,

yes, the spraying distance for WC86Co10Cr4 powder with a particle size < 22 μm for HVOF-burners with short nozzle (MEC 2700) should be in the range 200-250 mm, since at this distance medium-sized particles (16-18 μm) reach the maximum velocity about 600-700 m/s.

There is no direct correlation between particle size and maximum layer thickness, you can apply very thick layers with very fine powder. The other way around, there is a limitation for particle size with minimum layer thicknesses (<50 µm): coarse powders are not suitable for thin layers.

Much more important is the fact that coarse powders need a lot more energy to spray. For this reason, the WCCoCr powders with a grain size of 22-45 µm can only be sprayed with powerful burners (> 200 KW: GTV-K2, Praxair Tafa JP-5000, Thermico-CJS and other), MEC 2700 is not suitable for such coarse powders.

Regards
Vadim
Reply
08-03-2020, 08:28 PM,
#8
RE: Best place to mesure coating temperature
(08-03-2020, 06:02 PM)Vadim Verlotski Wrote: Dear Vitor,

yes, the spraying distance for WC86Co10Cr4 powder with a particle size < 22 μm for HVOF-burners with short nozzle (MEC 2700) should be in the range 200-250 mm, since at this distance medium-sized particles (16-18 μm) reach the maximum velocity about 600-700 m/s.

There is no direct correlation between particle size and maximum layer thickness, you can apply very thick layers with very fine powder. The other way around, there is a limitation for particle size with minimum layer thicknesses (<50 µm): coarse powders are not suitable for thin layers.

Much more important is the fact that coarse powders need a lot more energy to spray. For this reason, the WCCoCr powders with a grain size of 22-45 µm can only be sprayed with powerful burners (> 200 KW: GTV-K2, Praxair Tafa JP-5000, Thermico-CJS and other), MEC 2700 is not suitable for such coarse powders.

Regards
Vadim

Thanks for the great help, Vadim!

Best Regards
Reply




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