Deposition efficiency of Metco 131VF

[raviswanadha]

Dear,
Gordon we are facing some powder clogging problem when using metco Very fine powders like metco 131VF resulting in high powder consumption.
we are using 9MB system with 9Mpcl powder feeder and 10MR power supply.

We are currently using the following parameters for the 131VF powder.
1. GP Nozzle.
2. A pickup shaft
3. 500 Amps
4. 75 – 80 volts
5. 23gms / min.
6. 65- 90 mm spray distance.
7. We are pre heating the powder to 80ºc to remove the moisture if any.

please suggest me a method to improve the powder consumption rate and minimize the wastage.
regrards
Ravi Kumar

[Gordon]

Hi Ravi

Could you describe your problem in more detail? Is the powder feed pulsing? just stopping? Is pick-up shaft, hose or powder port clogging/fouling?

It does sound like a powder feeder problem or powder condition problem. So make sure powder feeder is serviced and thoroughly check for leaks. Make sure your powder is not getting damp, unfortunetly, even heating and drying already damp powder will not really help.

[raviswanadha]

Hi Ravi

Could you describe your problem in more detail? Is the powder feed pulsing? just stopping? Is pick-up shaft, hose or powder port clogging/fouling?

It does sound like a powder feeder problem or powder condition problem. So make sure powder feeder is serviced and thoroughly check for leaks. Make sure your powder is not getting damp, unfortunetly, even heating and drying already damp powder will not really help.

Hi Gordon ,
as you have mentioned we are having powder clogging and some times the powder comes in bursts through the powder port. Also the the humidity levels at our works is relatively high. we have serviced the powder feeder and also replaced with a new pick up shaft.If the powder is picking up moisture then what is the method to get rid of the moisture in the powder before coating.We are facing this problem only with thsi 131VF powder only.
regards
Ravi

[Gordon]

Hi Ravi

Well, really the only way would be to place and keep your freshly delivered powder into a environmentally controlled storage area. I know some go the the extreme of storing powder in
warm ovens so that the powder never sees temperatures below dew point.

In my experience, a damp powder,(particularly fine ceramics and composites) is difficult to rescue. On drying, powder just tends to form cake or biscuit like lumps. Only remedy is to break this up and re-sieve.

Do your operators thoroughly tumble the powder before placing in the powder feeder? Are you using a vibrator on the powder feed hopper?

You could experiment using different powder port shaft type, powder feed hose diameter or shorter length if possible to see if you can get improvement in feed. I know some even try changing carrier gas flow to get the best feed, but beware this is a critical parameter setting and will effect the injection properties of the powder into the plasma.