Metco 204 cracking

[Christian_B]

Hi all,

we are trying to set up Metco 204 for a new project and keep having problems with cracks in the microstructure.

Equipment / Parameter details as follows:

- 3MB gun, GH nozzle,
- 5MPE feeder, pick-up shaft A

66 Volt / 600 Amps
45 gr/min. feed rate
Distance 70 mm (2,75 inch), angle 90°

We observed vertical cracks, propagation from the top downwards with up to 170 µm length.

Any suggestions ? Too much heat ? Our discussion here is currently towards less energy/heat by reducing voltage and also possibly increasing spray distance.

Thanks in advance !

Cheers, Christian

[demionkrishan]

Hi all,

we are trying to set up Metco 204 for a new project and keep having problems with cracks in the microstructure.

Equipment / Parameter details as follows:

- 3MB gun, GH nozzle,
- 5MPE feeder, pick-up shaft A

66 Volt / 600 Amps
45 gr/min. feed rate
Distance 70 mm (2,75 inch), angle 90°

We observed vertical cracks, propagation from the top downwards with up to 170 µm length.

Any suggestions ? Too much heat ? Our discussion here is currently towards less energy/heat by reducing voltage and also possibly increasing spray distance.

Thanks in advance !

Cheers, Christian

Hi Pal,
it can be many reason, first of all ,check your stand off distance, speed and feed .

I recommend Bond coat Powder as Metco Amdry962 and Top coat powder Metco 204 .

Parameters below
[b]for bond coat [/b]
Stand off Distance 4 inches
primary gas- Nitrogen 75Psi (Pressure) -110SCFH (flow)
Secondary gas Hydrogen - 50 Psi- pressure 0-15 SCFH flow,till you get 70V
500 Amp
70-75V
Nozzle "G" (better than GH for 3MBTD gun)
Electrode 2M11
Pick up shaft - B/C up on your coating thickness (refer metco manual) I used "C" Shaft
Spray rate 44g/min
Cooling Air Pressure 40Psi
Carrier Gas- 10-14psi

[b]for top coat [/b]
Stand off Distance 3.5 inches
primary gas- Nitrogen 75Psi (Pressure) -70-80SCFH (flow)
Secondary gas Hydrogen - 50 Psi- pressure 0-15 SCFH flow,till you get 70V
500 Amp
70-75V
Nozzle "G" (better than GH for 3MBTD gun)
Electrode 2M11
Pick up shaft - B/C up on your coating thickness (refer metco manual) I used "C" Shaft
Spray rate 73g/min
Cooling Air Pressure 40Psi
Carrier Gas- 10-14psi

Note: if you feel more heat on component add additional cooling air

regards,
Krishz

[plasmajet1990]

Hi,

Can you show us the photo with the microstructure ?

Ion

[Christian_B]

@plasmajet1990: unfortunately not at hand, I'll try to get our laboratory to take a picture on the the coming Monday

@demionkrishan: thanks a lot, we are running a modified test today, I'll keep the forum posted on the results. By the way, it is Metco 204NS-G to be more precise.

Cheers, Christian

[Christian_B]

Here's a picture (low resolution, better version on Monday)

Christian

[demionkrishan]

@plasmajet1990: unfortunately not at hand, I'll try to get our laboratory to take a picture on the the coming Monday

@demionkrishan: thanks a lot, we are running a modified test today, I'll keep the forum posted on the results. By the way, it is Metco 204NS-G to be more precise.

Cheers, Christian

You are welcome Christian. Which I have send above will suit perfect for 204NS-G Metco Powder. hope you will get good output in future.

cheers,
Krishz

[loriolo]

Hi Krishz

In this case the only solution is to change powder productor I had several problem with it, has too many fines and very low DE

[Christian_B]

Hi folks,

thanks for the support from the forum, Metco 204 now works fine. It has been definitely too much heat causing the cracking, increasing the distance, lowering voltage and increasing powder feed rate led to success.

Details as follows (3MB gun):

Stand off Distance 4,5 inches
primary gas - Argon - 65 PSI
Secondary gas - Hydrogen - 43 PSI pressure
600 Amp / 60 V
Nozzle "GH"
Pick up shaft "B"
Powder feed rate 75 g/min
Cooling Air Pressure 36 PSI
Carrier Gas- 55 PSI

Coating microstructure now has no detectable cracks and 10-15 % porosity (25% upper linit), just perfect.

best regards, Christian

[J!m]

Personally I prefer 500 amps for 204... I know the Swiss prefer 600 amps due to their heavy use of the F4 gun.

I'm glad you had success! And I also agree with the above poster who said to run a B or C shaft in the feeder. Make sure when you change shaft to the smaller one, you also change the powder hose to orange and (if you are using one) the small braided hose and any bulkhead fitting should also be changed. Changes in the diameter of the feed line will set up oscillations in the flow, which can lead to pulsation in extreme cases.