Help: suitable Thermal Spray gun
10-31-2008, 02:49 AM,
#1
Help: suitable Thermal Spray gun
Hello there,

We are trying to make a house-built thermal spray unit for making titanium alloy coatings. We wish to be able to control the plasma temperature (if we are going to use plasma spray). Of course, titanium is so reactive with oxygen/nitrogen, we need a protective atmosphere.
Any idea/information about what type of gun, make, model? Any suggestions on building this sort of unit?

Thanks a lot.
pengc
Reply
10-31-2008, 06:39 AM,
#2
RE: Help: suitable Thermal Spray gun
Hi Pengc,
I would recommond you Metco 9MB gun.
Shabi
Reply
10-31-2008, 08:29 AM,
#3
RE: Help: suitable Thermal Spray gun
Hi,
When you are looking for options then it is suggested that you ask for coating samples from all the vendors. But of course the new HVOF systems that are available in the market are not only economical but the results exceed the performance that of plasma (like porosity, hardness etc).
Apart from SM you can try FST for plasma.
Also for HVOF try MEC-India, Tafa, DJ. MEC products are quite resonably priced.
Regards
Girish
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11-01-2008, 06:32 PM,
#4
RE: Help: suitable Thermal Spray gun
Hi Pengc,

Sign0016 to the Surface Engineering Forum.

Depending on the quality of the titanium coating required you could approach this in different ways.

* HVOF or better cold spray (cold gas-dynamic spraying)

* Plasma spray using (ideally argon or argon/helium plasma, avoiding hydrogen and nitrogen) with an argon shroud device or simple positive pressure enclosure.

* Arc spray using argon atomising gas and argon shroud device or simple positive pressure enclosure.

(not sure if the likes of Sulzer Metco supply shrouds, but it should not be too much trouble for you to design and make specific for your own use and needs)

* VPS or LPPS. Plasma gun and process conducted within a vacuum or low pressure argon chamber. Best coatings, but by a long way the most expensive.
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11-03-2008, 03:05 AM,
#5
RE: Help: suitable Thermal Spray gun
Thanks alot. Really useful. But I wonder if HVOF will do or not? I am not that confident with it because of oxygen thing.


(11-01-2008, 06:32 PM)Gordon Wrote: Hi Pengc,

Sign0016 to the Surface Engineering Forum.

Depending on the quality of the titanium coating required you could approach this in different ways.

* HVOF or better cold spray (cold gas-dynamic spraying)

* Plasma spray using (ideally argon or argon/helium plasma, avoiding hydrogen and nitrogen) with an argon shroud device or simple positive pressure enclosure.

* Arc spray using argon atomising gas and argon shroud device or simple positive pressure enclosure.

(not sure if the likes of Sulzer Metco supply shrouds, but it should not be too much trouble for you to design and make specific for your own use and needs)

* VPS or LPPS. Plasma gun and process conducted within a vacuum or low pressure argon chamber. Best coatings, but by a long way the most expensive.
Reply
11-03-2008, 10:24 AM,
#6
RE: Help: suitable Thermal Spray gun
Hi,
Actually it is misinterpreted many times regarding HVOF that they produce more oxides because of free oxygen. Well if you see the dwell time of particle in flame is very less. Because of which less chance for oxidation is there. However some finer particles will oxidize but in very small quantity. Actually results are encouraging with NiCrAlY.


Actually if parameters are correct you will get oxides in traces with HVOF.

Alternatively you can also try D Gun. It will produce still less oxides than HVOF.

Regards
Girish
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11-03-2008, 11:37 AM,
#7
RE: Help: suitable Thermal Spray gun
Hi Pengc,

Quote:Thanks alot. Really useful. But I wonder if HVOF will do or not? I am not that confident with it because of oxygen thing.
Out of the spray methods I suggested HVOF (may be mention HVAF here as well) will probably be the worst for absorption of gases (oxygen, nitrogen, hydrogen). This process also will not lend itself for spraying in protective atmospheres as the flame itself is not protective and because of high energy and flow rates would be difficult to contain in a protective chamber or shroud. The production of visible oxides as seen in many metallic coatings in itself is not the problem, titanium has an affinity to absorb gases. Oxygen, nitrogen and hydrogen seriously embrittle and stress titanium coatings. In saying that though, out of all the thermal spray processes not using additional protective atmospheres, HVOF/HVAF would be best (excluding cold spray) as per Girish's comments. With the right cut of powder and tight control on powder fines, HVOF/HVAF tuned to spray in a solid state manner rather than melting the powder may produce acceptable coatings (I have not HVOF sprayed titanium so this is theoretical Happy0193). Shrouding plasma and arc spray in argon I know from practical experience does make a huge difference when compared to normal spraying conditions. It really depends on what you require from the coatings at the end of the day. If you need very clean and ductile coatings, then probably the very expensive VPS/LPPS processes will be the only option.

I think you need to get samples sprayed with the various processes and test for acceptability for your particular application.
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11-04-2008, 04:17 PM,
#8
RE: Help: suitable Thermal Spray gun
(10-31-2008, 02:49 AM)pengcao Wrote: Hello there,

We are trying to make a house-built thermal spray unit for making titanium alloy coatings. We wish to be able to control the plasma temperature (if we are going to use plasma spray). Of course, titanium is so reactive with oxygen/nitrogen, we need a protective atmosphere.
Any idea/information about what type of gun, make, model? Any suggestions on building this sort of unit?

Thanks a lot.
pengc

Witch titanium alloy do you want spray?
For T40 you can use atmospheric plasma spraying with Argon - helium, or use coldspray, or use VPS from worst to best.
For TA6V, coldspray not have good results as I know, but you can use atmospheric plasma or best VPS.
Reply
02-19-2009, 08:16 PM, (This post was last modified: 07-17-2009, 02:13 PM by djewell.)
#9
RE: Help: suitable Thermal Spray gun
We have had very good results with HVAF sprayed titanium. Oxygen content in the coating was very low because of the short dwell time in the flame, solid particles, and lack of available oxygen in the flame. The flame consumes most of the oxygen, so it cannot combine with the titanium. Solid particles are much less reactive than molten particles.
Reply
02-20-2009, 06:17 AM,
#10
RE: Help: suitable Thermal Spray gun
(10-31-2008, 02:49 AM)pengcao Wrote: Hello there,

We are trying to make a house-built thermal spray unit for making titanium alloy coatings. We wish to be able to control the plasma temperature (if we are going to use plasma spray). Of course, titanium is so reactive with oxygen/nitrogen, we need a protective atmosphere.
Any idea/information about what type of gun, make, model? Any suggestions on building this sort of unit?

Thanks a lot.
pengc


Hi Pengc,

I agree with gordon's suggestion. You better to try with coated samples of differerent systems. As of now thermal spray hardware is very expensive matter. So, you need to work on the economics also. Just find out the type of your requirement, Does this work only intendedfor research work or to provide service to industries. If it is service oriented then you better to work on process costing.

For selecting suitable process you need to concentrate on the following.

1. Type of substrate
2. Availble working fuels ( power, gases, air etc)
3. Required properties of substrate after coating
4. TEst Values obtained after coating for each thermal spray process variant

After comparing all the above values you will defenetly come to a conclusion to select an appropriate coating system.

with regards
Karunanidhi
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