Plasma spray or HVOF ?

[Julio VALLES]

First of all, thank's for giving me access to this forum.

For some applications, I've got problems to decide which thermal spray process is most adequate...
Are there any established preferences/rules to use plasma spray or HVOF for the following coatings :

1) abradable coatings
2) coatings on composite and polymer substrates

Or does it depend on the coated materials (HVOF best for metal, carbide cermets..., plasma spray best for high t? ceramics...)

[Gordon]

Hi Julio VALLES

Welcome to the Surface Engineering Forum.

Generally, I would say that plasma spray is the more versatile tool as it is capable of spraying a wider range of materials, but HVOF can produce superior quality coatings, particularly some of the metal and carbide based coatings (assuming powder is optimised for particular process).

Abradable coatings - from practical experience I can only really comment on aluminium silicon alloy/polymer composite abradable coatings through both processes. I believe HVOF can have benefits in this case (density, strength and deposit efficiency). It is important to note that powder composition and particle sizes need to be adjusted fairly radically to produce equivalent type coatings (abradability wise). A powder developed for plasma spraying will usually produce a softer coating when sprayed with HVOF, which at first seems surprising, but the polymer constituent appears to have better deposit efficiency and produces a coating richer in polymer and hence lower hardness. Generally, the only reasons I see for not using HVOF for other abradable coatings is where porosity is the main criteria for controlling abradability or for use with powders graded for use with plasma where equivalent coatings are required.

Coatings on composite and polymer substrates - In my experience plasma spray is very much easier and more successful in this case. It is difficult to control the aggressive nature of HVOF spray on very soft and thermally sensitive substrates.

Generally your last statement is correct. Substrate material and geometry can also be factors (HVOF requires longer spray distances and heats substrates more aggressively).
Note different equipment makes and processes usually require powders to be graded differently to produce optimum coatings, so take care with your choice of powder for your particular process.

[Julio VALLES]

Gordon,

Thank's for your prompt response, which I find much relevant

Julio

[Danns]

Julio,

What type of material are you spraying?

Danns

[ENRIQUE.VALDERRAMA]

Hi Everybody,

I am comparing a vacuum arc source for coating and HVOF.

and I wonder why HVOF are famous to have better adhesion and be able to coat thicker films.


Best Regards,
Enrique

(08-23-2006 05:50 PM)Gordon Wrote:  Hi Julio VALLES

Welcome to the Surface Engineering Forum.

Generally, I would say that plasma spray is the more versatile tool as it is capable of spraying a wider range of materials, but HVOF can produce superior quality coatings, particularly some of the metal and carbide based coatings (assuming powder is optimised for particular process).

Abradable coatings - from practical experience I can only really comment on aluminium silicon alloy/polymer composite abradable coatings through both processes. I believe HVOF can have benefits in this case (density, strength and deposit efficiency). It is important to note that powder composition and particle sizes need to be adjusted fairly radically to produce equivalent type coatings (abradability wise). A powder developed for plasma spraying will usually produce a softer coating when sprayed with HVOF, which at first seems surprising, but the polymer constituent appears to have better deposit efficiency and produces a coating richer in polymer and hence lower hardness. Generally, the only reasons I see for not using HVOF for other abradable coatings is where porosity is the main criteria for controlling abradability or for use with powders graded for use with plasma where equivalent coatings are required.

Coatings on composite and polymer substrates - In my experience plasma spray is very much easier and more successful in this case. It is difficult to control the aggressive nature of HVOF spray on very soft and thermally sensitive substrates.

Generally your last statement is correct. Substrate material and geometry can also be factors (HVOF requires longer spray distances and heats substrates more aggressively).
Note different equipment makes and processes usually require powders to be graded differently to produce optimum coatings, so take care with your choice of powder for your particular process.

[fahad03092]

Dear all,

I am new in this forum. Thanks for giving me permission to be a member in this group. I have a question?

What is the difference between metco 9M and metco 9MB or 9MC?

Also How do I know How much powder I need for spray?


Thanks a lot in advance.

[derek]

9MB is Sulser Metco's plasma gun, 9MC is the controller. 9MP is the powder feeder, 9M ????????????

For the powder, you need to count how long time you spray and the powder feed rate.

[fahad03092]

People says in literature that they use metco 9M equipment. Now how can I understand which torch they use? Metco 7MB or 9MB or 3MB or SG 100 or any others?

[djewell]

You should also include HVAF in your comparison if you are after low oxide, high bond strength coatings. HVAF is an economical process to apply both metals and cermets to parts at high production rates. Unlike plasma and HVOF, HVAF guns do not burn through spare parts. The guns are robust and provide consistent coatings.

[kschewe]

Hi guys
There are 2 models of the 9mb
First one is the 9m and is handheld gun with a handle
Second one is 9mb which is machine mount for a robot etc.

there is a 3mb which can be hand held or machine held.
there is 3mbII which is the same but can handle more power
it is small so we use it as an id gun

7mb and others are older equipment.

11mb is a id gun

sg100- 2086 or 2700
is a praxair small id gun.

we have many lol

[fahad03092]

Can anyone please give me idea how much powder at least I need to put in powder hopper to get a coatings. I want to spray Calcium phosphate with powder feed rate 20 g/min. We have plasma technik powder feeder.

Thanks a lot.

[Gordon]

(10-07-2011 01:36 AM)fahad03092 Wrote:  Can anyone please give me idea how much powder at least I need to put in powder hopper to get a coatings. I want to spray Calcium phosphate with powder feed rate 20 g/min. We have plasma technik powder feeder.

Thanks a lot.

Hi fahad03092

I think you will need to give us far more information to even attempt to answer your question.

You don't tell us:
spray equipment
parameters used
part to be sprayed, size, area, coating thickness
Powder details

Also, this may be better posted as a new thread as I don't think its really related to the topic of this thread.