Problem with Metco 601NS & F4

[paikhuan]

Hi everyone!!

I followed during a long time this forum and, now, i need to post due to a problem with a new part.

We are developing a new part with metco 601Ns & F4. We were working during years with other setups powder-gun but, now, we are experiencing problems.

When we spraying test coupons, there is no problem, the whole coating microstructure is ok, hardness too(70-72 HR15Y). But, when we did the part, we are getting some problems with the surface finish. I think that we are having problems with turbulence, setup of the airjets or something related.

I posted a picture of the part.
[url=<a][/url]

I tried to change the crossing distance of the airjets in the last passes of the last part, and it seems we have obtained a slight improvement, but i am scared to develop a working route with bond coat parallel airjets & top coat crossing airjets.

Could u help me?

Parameters are basically from Oerlikon Metco.

[Benjamin101]

Hi There,

This coating is often machined after spraying to the required diameter/dimensions, is this not the case in your specific application? I have seen similar surface finish on a part i am developing, but not quite as rough as this. But, as my part is turned afterwards and the top layers of material are removed, i am not concerned.

Regards,

Ben

[Vadim Verlotski]

Hi,
The coating on the picture has a problem with overspray. If you don't want to change the powder and spray parameters, then the only option is with air cooling:
You need continuous cooling with a short distance to the component and high air pressure. If the air jet is strong enough near the spray area, the problem with overspray will be solved and you will get a smooth coat.

[paikhuan]

Hi There,

This coating is often machined after spraying to the required diameter/dimensions, is this not the case in your specific application? I have seen similar surface finish on a part i am developing, but not quite as rough as this. But, as my part is turned afterwards and the top layers of material are removed, i am not concerned.

Regards,

Ben

Hi Ben,

It is our case. Coating is machined after spraying, but, it has a non-uniformity color due to this fact. This problem (both of them: appearence and inhomogenity) does not appear in monitoring coupons.

Hi,
The coating on the picture has a problem with overspray. If you don't want to change the powder and spray parameters, then the only option is with air cooling:
You need continuous cooling with a short distance to the component and high air pressure. If the air jet is strong enough near the spray area, the problem with overspray will be solved and you will get a smooth coat.

Hi Vadim,

So, it is possible to reduce this overspray crossing the aijets? What kind of setup? Maybe 30-40 mm after the spray distance?

For example:
Spray distance : 100 mm
Air jet Crossing distance: 130 mm
Pressure : 5 bar

Thanks in advance guys,

[Vadim Verlotski]

Hi,
I better point to pictures how I solved the problem with overspray on Axial III:

Figure 1. Coating without a running cooling system.
Figure 2. Coating surface quality without cooling system on robot.
Figure 3 and 5. Homemade cooling system on the robot.
Figure 4. Coating surface quality with new cooling system.

[paikhuan]

Hi,
I better point to pictures how I solved the problem with overspray on Axial III:

Figure 1. Coating without a running cooling system.
Figure 2. Coating surface quality without cooling system on robot.
Figure 3 and 5. Homemade cooling system on the robot.
Figure 4. Coating surface quality with new cooling system.

Thank you so much Vadim,

Very interesting your pictures and information.
 I am wondering about the setup of your axial gun and crossing distance of airjets. Any idea how to do the setup? Some rule to positioning these airjets? I am scared about the possibility of lost DE because a bad setup of the distance.


Kind regards,

[Vadim Verlotski]

Hi,
In my case, the spraying distance was about 100 mm, and the distance from the cooling nozzles to the parts was about 30 mm. Four nozzles were located at such angles that air flows did not intersect with the flame of the plasma torch at a distance of less than 150 mm. Thus, when spraying from a distance of 100 mm, air flows did not fall on the spray spot, but surrounded it from all sides at a distance of about 20 mm. The air flow in the nozzles was regulated by a common manual valve, the position of which was selected empirically according to preliminary experiments. Air pressure in front of the valve 6-8 bar.
Of course, powerful air flows around the spray spot somewhat reduce the DE, but this is more than offset by an improvement in the quality of the coating.

[paikhuan]

Hi guys!!

Second round.

We changed the position and crossing distance of the airjets and it works!

Now, we are experiencing some problems with non-homogeneity of the coating. We are working with other guns and abradable and never saw something similar.

As-Sprayed



(it can be seen that there are problems with coating)

Machined



I think that we are getting problems with the powder injection or rotation. Parameters are based on Oerlikon standard for F4 but changing the spraying distance. 

It is possible that the problem is related with carrier gas? (9.0 slpm Ar) 
It is possible that the problem is related with transverse speed and rotation? 4 mm/s and 60 rpm. Or maybe with the step? 4 mm for F4.

I am very exhausted....

Kind regards,

[Lemster68]

Your RPM and traverse speed are useless without also providing the part diameter.

[Gordon]

Hi Paikhuan

The powder is a blend and will naturally classify  during injection, so the denser particles tend to penetrate the plasma further. If you were to spray the coating without movement you would find the deposit  aluminium rich on one side and  polyester rich on the other.

To ease your problem change the powder port or gun orientation so that injection is in line with rotation direction.

[paikhuan]

Your RPM and traverse speed are useless without also providing the part diameter.

sorry, i forgot to explain:

Diameter: 780 mm

@Gordon. Thanks, i will try  to do this