surface speed for HVOF

[Zhiguo]

Hello friends!

I have a question about the surface speed(the relative speed between part surface and HVOF flame) during HVOF.
I found a sentence in our HVOF program " surface speed 100m/min". Does it mean that the surface speed must be 100m/min?( we use JP5000ST gun)
Is the surface speed value different between different gun?

[wilfred1963]

It really depends on the diameter of the part slower speeds for larger parts and the deposition your trying to achieve per pass to slow on your part speed and you'll barber poll or stripe it as far as gun type i don't think it matters much matching the feeds and speeds is the best way to go and keeping the part temp. with in limits.

[derek]

I prefer to use 500 -700 mm/s speed during HVOF spray if the part is not rotating.

[ServiceTech]

Hi;

The ultimate surface speed for HVOF applications is mainly dependent on powder feed rate, DE%, material composition and equipment type.

For most HVOF applications, a coating deposition rate of .0002 - .0003" coating deposit per pass is desirable. This deposition rate is based on .125 - .1875" gun offset (overlap).

Typically, I've found that 400 sf/min to be a good starting point. I know of others who find 250 sf/min satisfactory. Just remember to try and achieve the .0002 - .0003" deposition / pass based on .125 - .1875" offset.

To find your gun traverse rate for rotating parts:

RPM x Offset

Example: 70 rpm x .125" = 8.75" / min gun traverse rate.
Convert to mm/sec: 8.75 x 25.4 / 60 = 3.7 mm/sec

Hope this helps,

Ross

[derek]

For application of MCrAlY coating, I put 0.001-0.0015" per pass, for WC-Co coating I put 0.0005" per pass using JP5000.
If I use DJ gun, the number will be lower.

[Gordon]

Hi Zhiguo

You may have noticed the term "coating deposition rate per pass" from ServiceTech and Derek . This in my view is the more important parameter. Achieve the desired deposition per pass and this will give you the surface speed you require. Carbide and ceramic based coatings in particular benefit from low deposition per pass (0.0002" or 5μm per pass about optimum). There will be situations where this is hard to achieve, the goal then is to get as low as possible. There are materials which are far more tolerant and even a few which benefit from high deposition rates like some bond coats.

[Zhiguo]

Thank you for all your good information!

[loriolo]

I agree with all said till now, but your question was about the minimum peripheral speed of the part regards to the gun, which is different for every spray process, thermal spray -35 m/min, Arc spray-100 m/min, Plasma spray 75 m/min, HVOF-120 m/min, then you must apply the formulas explained before.
Regards

[Gordon]

(02-28-2011 11:27 PM)loriolo Wrote:  I agree with all said till now, but your question was about the minimum peripheral speed of the part regards to the gun, which is different for every spray process, thermal spray -35 m/min, Arc spray-100 m/min, Plasma spray 75 m/min, HVOF-120 m/min, then you must apply the formulas explained before.
Regards

First, no disrespect for the quoted minimum peripheral speeds for various processes, generically they work in many cases. But speeds should not be generically set in stone as a parameter. Thermal spray process type really is a relatively minor consideration - far more heat is transferred to the treated part by the deposited coating than by heating effect of the spray gun alone without coating deposition.

More important are are those other factors that effect deposition rate and temperature. Also the nature of the coating being applied and substrate.

A few points to highlight my view:

Would you spray coatings with same speed settings if one had a feed rate of 2lb/hr compared to a second with 50lb/hr?

Would you spray a NiAl bond coat or a "one-step" coating at the same speed settings as a ceramic or carbide coating?

Would you use the quoted speeds above if you were to apply a coating to a delicate substrate say of very thin section or of plastic or paper?

Speeds and feeds should be a consequence of more important parameter settings in my opinion.

[loriolo]

I agree with you, minimum peripheral speeds is a start point, and then as you said, it is necesary to know the powder technicall propriety and spray proces, in order to define the most correct peripherical speed or translation speed, in accordance with the spray rate, maximum/minimum layer thickness, and so on
.

[ServiceTech]

I couldn't have said it better myself Gordon. Thickness deposit rate/pass at a given gun offset is a critical point when communicating in regards to coating parameters.

(03-03-2011 07:53 PM)Gordon Wrote:  

(02-28-2011 11:27 PM)loriolo Wrote:  I agree with all said till now, but your question was about the minimum peripheral speed of the part regards to the gun, which is different for every spray process, thermal spray -35 m/min, Arc spray-100 m/min, Plasma spray 75 m/min, HVOF-120 m/min, then you must apply the formulas explained before.
Regards

First, no disrespect for the quoted minimum peripheral speeds for various processes, generically they work in many cases. But speeds should not be generically set in stone as a parameter. Thermal spray process type really is a relatively minor consideration - far more heat is transferred to the treated part by the deposited coating than by heating effect of the spray gun alone without coating deposition.

More important are are those other factors that effect deposition rate and temperature. Also the nature of the coating being applied and substrate.

A few points to highlight my view:

Would you spray coatings with same speed settings if one had a feed rate of 2lb/hr compared to a second with 50lb/hr?

Would you spray a NiAl bond coat or a "one-step" coating at the same speed settings as a ceramic or carbide coating?

Would you use the quoted speeds above if you were to apply a coating to a delicate substrate say of very thin section or of plastic or paper?

Speeds and feeds should be a consequence of more important parameter settings in my opinion.