95 MXC Porosity
08-29-2019, 09:07 PM,
#1
95 MXC Porosity
Hello,

My company has just purchased a TAFA 8830 Arc Spray System.

The first coating performed with the machine was TAFA 95 MXC on AISI-1020 steel substrate.

The applied layer was approximately 2.0 mm with the following (bulletin) parameters:
Voltage (V): 34;
Amperage (A): 150;
Air Pressure (psi): 50;
Air Cover: Blue;
Nozzle Positioner: Short cross;
Standoff Distance (mm): 180-200;

Our results were not as expected. After grinding with green silicon carbide wheel the piece showed a lot of porosity. Theoretically this coating should have less than 1% porosity resulting in excellent finish, correct?

Is there any possible solution considering the information I provided?

Thank you all.


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08-30-2019, 05:54 AM,
#2
RE: 95 MXC Porosity
(08-29-2019, 09:07 PM)vcduramais Wrote: Hello,

My company has just purchased a TAFA 8830 Arc Spray System.

The first coating performed with the machine was TAFA 95 MXC on AISI-1020 steel substrate.

The applied layer was approximately 2.0 mm with the following (bulletin) parameters:
Voltage (V): 34;
Amperage (A): 150;
Air Pressure (psi): 50;
Air Cover: Blue;
Nozzle Positioner: Short cross;
Standoff Distance (mm): 180-200;

Our results were not as expected. After grinding with green silicon carbide wheel the piece showed a lot of porosity. Theoretically this coating should have less than 1% porosity resulting in excellent finish, correct?

Is there any possible solution considering the information I provided?

Thank you all.


It is completely normal for Arc Spray Process. There are no pore-free coatings that are applied with this method. With fine adjustment of the parameters, you may be able to achieve a lower porosity, but for a significant improvement you need quite different spraying techniques.

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09-02-2019, 06:28 AM,
#3
RE: 95 MXC Porosity
Increase air pressure so melted particules will be more fine. Then reduce layer thickness around 20 microns.
Do you have same issue with other wires?
How do you prepare surface? Do you have a bonding layer?
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09-02-2019, 11:43 AM,
#4
RE: 95 MXC Porosity
(09-02-2019, 06:28 AM)velocity Wrote: Increase air pressure so melted particules will be more fine. Then reduce layer thickness around 20 microns.
Do you have same issue with other wires?
How do you prepare surface? Do you have a bonding layer?

Thank you for your answer. I'll try this.
With other wires the porosity is extremely lower, but a few always exist.
The preparation of the surface is made with machining, brown Al2O3 blasting and bond layer (TAFA 75B).
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09-03-2019, 07:21 PM,
#5
RE: 95 MXC Porosity
What about your finishing process????

Grinding or Machining??
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09-03-2019, 07:30 PM,
#6
RE: 95 MXC Porosity
(09-03-2019, 07:21 PM)Met.Eng. Wrote: What about your finishing process????

Grinding or Machining??

"grinding with green silicon carbide wheel"
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09-05-2019, 07:47 AM,
#7
RE: 95 MXC Porosity
Also please reduce standoff to 120 mm and v to 30
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09-05-2019, 01:46 PM,
#8
RE: 95 MXC Porosity
Dear all.

Thanks for big help.

Here is what I did based on your help and some instructions from Praxair:

Positioner nozzle: form short cross to long cross;
Air cape: from blue to green;
Distance: from 180 to 65 mm;
Amperage: from 150 to 100 A;
Surface speed: from 40 to 70 m/min.

Tell me about the results. Do you think it can get any better?


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09-09-2019, 05:46 PM,
#9
RE: 95 MXC Porosity
I think it seems very well. Apply a liquid penetration test to see pores if there are any.
Good job.
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