Turbulent 450ns Microstructure.
09-21-2015, 02:57 AM,
#1
Turbulent 450ns Microstructure.
Hi all,

I have problems with the coating microstructure 450ns. The coating microstructure is not laminar. See parameters and attachment samples.

Hydrogen (SCFH) 22
Argon (SCFH) 100
Carrier Gas (SCFH) 5
Airjet (PSI) 75
Distance (INCH) 5
Angle 85° to Spray Surface
Table Speed (RPM) 60
Feedrate (LB/HR) 8.6
Voltage (V) 67
Current (A) 500

Has anyone getting such microstructure and found the root cause? Any help would be very much appreciated.

Regards
alvin


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09-23-2015, 11:00 AM,
#2
RE: Turbulent 450ns Microstructure.
(09-21-2015, 02:57 AM)alvliew Wrote: Hi all,

I have problems with the coating microstructure 450ns. The coating microstructure is not laminar. See parameters and attachment samples.

Hydrogen (SCFH) 22
Argon (SCFH) 100
Carrier Gas (SCFH) 5
Airjet (PSI) 75
Distance (INCH) 5
Angle 85° to Spray Surface
Table Speed (RPM) 60
Feedrate (LB/HR) 8.6
Voltage (V) 67
Current (A) 500

Has anyone getting such microstructure and found the root cause? Any help would be very much appreciated.

Regards
alvin

You can get some idea from here https://www.google.co.uk/patents/US7371352

A flow of fuel-air mixture causes the flow to become more turbulent.


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Metallurgy and Materials Engineering
Engineering Community
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09-25-2015, 10:46 AM, (This post was last modified: 09-25-2015, 11:50 AM by Joris Kraak.)
#3
RE: Turbulent 450ns Microstructure.
Hi Alview,

We had the same problems with the Inconel 625 and the reason is: Air Jets (turbulent flow) as megaloman already indicated!

You have to think in 3D simulating the spray stream. The area where plasma stream and air flow come together is a lot of turbulence creating this semi molten particles in your coating. I must say the coating itself looks not bad at all, nice job! (apart from that inclusions)

It is not so easy to solve this problem because it is very sensitive, but for our Inconel 625 the following had some improvement:

1. we positioned the powder impact area better onto the part, make sure 90 degree or as close as possible.
2. lower your air jets, we use now only 15PSI with good results. The diameter of our air jet I need to check.
3. In your parameters I would suggest crank the carrier gas a little higher (what injector diameter are you using?)
4. we positioned our air jets on 90 degree onto part. Injected from top air jets on sides.
5. If you are coating a flat surface (rotating?) make sure you have enough air to blow all the dust away and close to you dust extraction unit.

I is a tough problem but you need to try some different setting with your air jets.

Good luck,
Joris


(09-21-2015, 02:57 AM)alvliew Wrote: Hi all,

I have problems with the coating microstructure 450ns. The coating microstructure is not laminar. See parameters and attachment samples.

Hydrogen (SCFH) 22
Argon (SCFH) 100
Carrier Gas (SCFH) 5
Airjet (PSI) 75
Distance (INCH) 5
Angle 85° to Spray Surface
Table Speed (RPM) 60
Feedrate (LB/HR) 8.6
Voltage (V) 67
Current (A) 500

Has anyone getting such microstructure and found the root cause? Any help would be very much appreciated.

Regards
alvin

Reply
09-25-2015, 11:53 AM, (This post was last modified: 09-25-2015, 12:01 PM by Joris Kraak.)
#4
RE: Turbulent 450ns Microstructure.
One picture with more or less same problem and another where we changed air jets.


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09-28-2015, 02:34 AM,
#5
RE: Turbulent 450ns Microstructure.
(09-25-2015, 10:46 AM)Joris Kraak Wrote: Hi Alview,

We had the same problems with the Inconel 625 and the reason is: Air Jets (turbulent flow) as megaloman already indicated!

You have to think in 3D simulating the spray stream. The area where plasma stream and air flow come together is a lot of turbulence creating this semi molten particles in your coating. I must say the coating itself looks not bad at all, nice job! (apart from that inclusions)

It is not so easy to solve this problem because it is very sensitive, but for our Inconel 625 the following had some improvement:

1. we positioned the powder impact area better onto the part, make sure 90 degree or as close as possible.
2. lower your air jets, we use now only 15PSI with good results. The diameter of our air jet I need to check.
3. In your parameters I would suggest crank the carrier gas a little higher (what injector diameter are you using?)
4. we positioned our air jets on 90 degree onto part. Injected from top air jets on sides.
5. If you are coating a flat surface (rotating?) make sure you have enough air to blow all the dust away and close to you dust extraction unit.

I is a tough problem but you need to try some different setting with your air jets.

Good luck,
Joris


(09-21-2015, 02:57 AM)alvliew Wrote: Hi all,

I have problems with the coating microstructure 450ns. The coating microstructure is not laminar. See parameters and attachment samples.

Hydrogen (SCFH) 22
Argon (SCFH) 100
Carrier Gas (SCFH) 5
Airjet (PSI) 75
Distance (INCH) 5
Angle 85° to Spray Surface
Table Speed (RPM) 60
Feedrate (LB/HR) 8.6
Voltage (V) 67
Current (A) 500

Has anyone getting such microstructure and found the root cause? Any help would be very much appreciated.

Regards
alvin
Hi Joris,
Thank you for your input and help. I am using port#2 (dia -1.85mm/0.073") for this experiment. I did not quite understand your suggestion in point#4. My apology. Here are the sketches for my setting for the air jets and the position of the injector.

regards
alvin



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10-01-2015, 03:35 AM,
#6
RE: Turbulent 450ns Microstructure.
Hi Alview,

If this is your set-up make sure the particles are deposited at 90 degree impact so that means not position the gun 90 degree but look at impact of particles!

With regards to point nr4 the set-up is fine, however you could also try to pinch the air jets a little into the flame to remove that excessive dust on the boundary of the plasma.

Carrier gas we are using 3.5 - 4.0 Nlpm

Spray a sample and have a look!

regards,
Joris
Reply
10-16-2015, 01:39 AM, (This post was last modified: 10-16-2015, 09:16 PM by Johnny_Blaze.)
#7
RE: Turbulent 450ns Microstructure.
(09-21-2015, 02:57 AM)alvliew Wrote: Hi all,

I have problems with the coating microstructure 450ns. The coating microstructure is not laminar. See parameters and attachment samples.

Hydrogen (SCFH) 22
Argon (SCFH) 100
Carrier Gas (SCFH) 5
Airjet (PSI) 75
Distance (INCH) 5
Angle 85° to Spray Surface
Table Speed (RPM) 60
Feedrate (LB/HR) 8.6
Voltage (V) 67
Current (A) 500

Has anyone getting such microstructure and found the root cause? Any help would be very much appreciated.

Regards
alvin

Hi alvliew,
Your parameters only mention an R.P.M. without any information of the diameter you are spraying on to calculate surface speed, also your traverse rate is missing in order to establish the step-size per rotation. This will have a major influence on the uniformity of the coating and if your air jets are at 70 psi pointing into the spray pattern that's a no-no.

30-40 psi is more than sufficient for your air jets, all your other parameters are ok..

Regards,
John
Reply
10-19-2015, 03:38 AM,
#8
RE: Turbulent 450ns Microstructure.
(10-16-2015, 01:39 AM)Johnny_Blaze Wrote:
(09-21-2015, 02:57 AM)alvliew Wrote: Hi all,

I have problems with the coating microstructure 450ns. The coating microstructure is not laminar. See parameters and attachment samples.

Hydrogen (SCFH) 22
Argon (SCFH) 100
Carrier Gas (SCFH) 5
Airjet (PSI) 75
Distance (INCH) 5
Angle 85° to Spray Surface
Table Speed (RPM) 60
Feedrate (LB/HR) 8.6
Voltage (V) 67
Current (A) 500

Has anyone getting such microstructure and found the root cause? Any help would be very much appreciated.

Regards
alvin

Hi alvliew,
Your parameters only mention an R.P.M. without any information of the diameter you are spraying on to calculate surface speed, also your traverse rate is missing in order to establish the step-size per rotation. This will have a major influence on the uniformity of the coating and if your air jets are at 70 psi pointing into the spray pattern that's a no-no.

30-40 psi is more than sufficient for your air jets, all your other parameters are ok..

Regards,
John

Hi John,

Thanks for the tips. the diameter of the fixture is 12" where the coupons are seated and the traverse rate is 2mm/sec. We are still getting this unwanted turbulence microstructure which maybe is the main culprit to the high porosity content. Please advise. Thank you very much.

Rgds
alv
Reply
10-19-2015, 07:21 AM, (This post was last modified: 10-26-2015, 10:24 PM by Johnny_Blaze.)
#9
RE: Turbulent 450ns Microstructure.
(10-19-2015, 03:38 AM)alvliew Wrote:
(10-16-2015, 01:39 AM)Johnny_Blaze Wrote:
(09-21-2015, 02:57 AM)alvliew Wrote: Hi all,

I have problems with the coating microstructure 450ns. The coating microstructure is not laminar. See parameters and attachment samples.

Hydrogen (SCFH) 22
Argon (SCFH) 100
Carrier Gas (SCFH) 5
Airjet (PSI) 75
Distance (INCH) 5
Angle 85° to Spray Surface
Table Speed (RPM) 60
Feedrate (LB/HR) 8.6
Voltage (V) 67
Current (A) 500

Has anyone getting such microstructure and found the root cause? Any help would be very much appreciated.

Regards
alvin

Hi alvliew,
Your parameters only mention an R.P.M. without any information of the diameter you are spraying on to calculate surface speed, also your traverse rate is missing in order to establish the step-size per rotation. This will have a major influence on the uniformity of the coating and if your air jets are at 70 psi pointing into the spray pattern that's a no-no.

30-40 psi is more than sufficient for your air jets, all your other parameters are ok..

Regards,
John

Hi John,

Thanks for the tips. the diameter of the fixture is 12" where the coupons are seated and the traverse rate is 2mm/sec. We are still getting this unwanted turbulence microstructure which maybe is the main culprit to the high porosity content. Please advise. Thank you very much.

Rgds
alv

Hi Alv,
Try bringing your RPM up to 64, that will give you an even 200 surface feet per minute. Unless that is the maximum RPM you can achieve.

I would also recommend that you increase your traverse rate from 2mm/sec to 6 mm/sec or even 8mm/sec. 450NS has a very large spray pattern at a 5 inch spray distance, which is perfect, and, you can safely increase your traverse rate to 6mm/sec and even 8mm/sec on a 12 inch diameter.

Increase the carrier flow to 8.0 scfh. Round up your feedrate to 9.0lbs/hr....this should reduce some of the unmelted and partially melted particles in the structure as well.

Currently, at 60 RPM this is giving you a linear speed of 188 sfpm, which is fine...just kind of odd to work with a constant of 188sfpm. This is why I suggest rounding it up to 200sfpm @ 64rpm.

Your step-size is a different issue, 2mm/sec on a 12 inch diameter is a step size of 2mm/rotation (~0.080'/rotation). I believe this may be the cause of your porous regions, when the step-size is too small and results in a slow traverse rate this can lead to an increase of particle re-entrainment, this can create some of those porous regions in your microstructure.

Increasing the traverse rate to 6mm/sec or 8mm/sec, at 9.0lbs/hour that should yield a deposition rate of approximately 0.0012"-0.001" per cycle, also minimizing heat input into the component and or test sample.

You're deposition rate will decrease substantially per scan or cycle, and the number of passes/cycles will increase, but, what you lose in deposition rate you will gain in coverage and the overall time it takes to spray the target thickness will be the same or possibly even lower.

Maintain your air-jets parallel, 30-40 psi, and cooling/vortex tubes away from the spray pattern, not to influence additional turbulence.

Just out of curiosity, how did you arrive at a traverse rate of 2mm per second, if you don't mind me asking?

Regards,
John
Reply
11-12-2015, 07:49 PM,
#10
RE: Turbulent 450ns Microstructure.
(09-28-2015, 02:34 AM)alvliew Wrote:
(09-25-2015, 10:46 AM)Joris Kraak Wrote: Hi Alview,

We had the same problems with the Inconel 625 and the reason is: Air Jets (turbulent flow) as megaloman already indicated!

You have to think in 3D simulating the spray stream. The area where plasma stream and air flow come together is a lot of turbulence creating this semi molten particles in your coating. I must say the coating itself looks not bad at all, nice job! (apart from that inclusions)

It is not so easy to solve this problem because it is very sensitive, but for our Inconel 625 the following had some improvement:

1. we positioned the powder impact area better onto the part, make sure 90 degree or as close as possible.
2. lower your air jets, we use now only 15PSI with good results. The diameter of our air jet I need to check.
3. In your parameters I would suggest crank the carrier gas a little higher (what injector diameter are you using?)
4. we positioned our air jets on 90 degree onto part. Injected from top air jets on sides.
5. If you are coating a flat surface (rotating?) make sure you have enough air to blow all the dust away and close to you dust extraction unit.

I is a tough problem but you need to try some different setting with your air jets.

Good luck,
Joris


(09-21-2015, 02:57 AM)alvliew Wrote: Hi all,

I have problems with the coating microstructure 450ns. The coating microstructure is not laminar. See parameters and attachment samples.

Hydrogen (SCFH) 22
Argon (SCFH) 100
Carrier Gas (SCFH) 5
Airjet (PSI) 75
Distance (INCH) 5
Angle 85° to Spray Surface
Table Speed (RPM) 60
Feedrate (LB/HR) 8.6
Voltage (V) 67
Current (A) 500

Has anyone getting such microstructure and found the root cause? Any help would be very much appreciated.

Regards
alvin
Hi Joris,
Thank you for your input and help. I am using port#2 (dia -1.85mm/0.073") for this experiment. I did not quite understand your suggestion in point#4. My apology. Here are the sketches for my setting for the air jets and the position of the injector.

regards
alvin

Hi, Try this. Im making the assumption that the part be coated is in rotation. These parameters are for a Metco 3M gun:

Argon Pressure: 100 psi
Argon Flow: 100 scfh
H2 pressure: 55 psi
H2 flow: ~18
Volts: 74
Amps: 500
Standoff of gun: 4"
Frontal intersect: 5"
Table RPM: 150 rpms
Powder Feed rate: 5 grams/min
Powder pressure: 100 psi
Carrier flow (Argon): 32 scfh
Traverse Rate: 7 mm/sec
#2 powder port and block
3MB Gun
GH nozzle
Disribution ring: Ar. Uni-jet

Try this. I use these parameters everyday with success.

Mike
Reply
11-17-2015, 12:43 PM,
#11
RE: Turbulent 450ns Microstructure.
Is your problem solved Alvview?
If not please send a picture of the set-up so I can have a look.

regards,
joris
Reply




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