Aluminum oxide+titanium oxide

[schumi]

Hi all,

I've been reading this forum for a time and finaly have decided to write a doubt.

I am performing a project and am spraying a coating with the 5P gun. The powder is the aluminum oxide+ 3% of titanium oxide of sulzer. I am spraying onto aluminum and am using Ni+5%Al as a bonding coating.
The thing is that I am not getting good results and I don't know why it is.
Here are the parameters that I have used:
-Oxigen: 3.4bar,flow 34
-Acetylene:1.3bar,flow 34
-Air:3bar
-Spraying distance: 85mm
-Powder rate: 8 clicks open

As I see, it is difficult to me to achieve a coarser coating. If the coating is coarser, it detaches. I also see that it is difficult to achieve an uniform coating. Can you see any problems in the photo I have sent? What about the parameters?

I've sent a mail to Gordon, hope he can insert the photo in this post.
Thanks for all

[derek]

You can check with Sulzer Metco for the parameter for their product. But I would use plasma to spray ceramic coating.

[Gordon]

Hi Schumi

to the Surface Engineering Forum.

I have inserted your image into your post above. Note I have taken liberty to resize image for thumbnail and larger view (click on image) which I hope is ok.

Are you using PSA or 2PSA (cross air jet accelerator)?

Could you describe in more detail the type of coating you want to achieve i.e. thickness, roughness etc.. and desired coating function.

[schumi]

Hi Schumi

to the Surface Engineering Forum.

I have inserted your image into your post above. Note I have taken liberty to resize image for thumbnail and larger view (click on image) which I hope is ok.

Are you using PSA or 2PSA (cross air jet accelerator)?

Could you describe in more detail the type of coating you want to achieve i.e. thickness, roughness etc.. and desired coating function.

I am not using any cross air jet accelerator.

I wanted to achieve 150micro meters of thickness. I don't care about the roughness. The function of the coating is to improve the wear resistance ofa pulley.

[Gordon]

Hi Schumi

I am not using any cross air jet accelerator.

I wanted to achieve 150micro meters of thickness. I don't care about the roughness. The function of the coating is to improve the wear resistance ofa pulley.

I would strongly recommend using a 2PSA air jet assembly on your gun and use the parameters listed in your gun manual for the specific powder. Spraying ceramic coatings without this attachment will only give you very porous and friable coatings, good for thermal barrier coatings, but very poor for dense and strong wear resistant coatings.

[djewell]

You may also consider changing your coating material to something that will spray better with your equipment. A tungsten carbide coating will give you excellent wear protection and can easily be applied to 150 um.

[Met.Eng.]

May be you can set the distance 70 mm to decrease poroses. But you must still use air jet my frd.

[schumi]

Hi all,
I have been installing the air jets and researching a bit but I still have a similar problem.
The parameters I have used are the same that recomend the manufacturer of the powder:
-Oxigen: 3.4bar,flow 34
-Acetylene:1.3bar,flow 34
-Air (jets):4.8bar
-Spraying distance: 60mm
-Powder rate: 6 clicks open
-Point that the jets get crossed: 50mm
I am not sure if I could spray this material properly with this process but sulzer told me that I could.
I have some questions about the picture I have sent to gordon:
-What problem do you see with this?
-Do you think that I could get a good coating?
-How could I get the microhardness values for this? This is because the coating isn't dense enough to see the indenters trace.
I would appreciate a lot your help.
Thanks for all

[Stephen Booth]

Just an insight, spraying Ceramics with a powder flame torch is challenging. However if you switch to Flame Rod spraying (Mogul or Rokide) you can spray even harder coatings like Cr2O3, with very good results (and the investment in the equipment about the same price as a 5PII torch. Something to think about, although the rods are much more expensive. Highly recommend the Rod Spray for those with limited budget and lower volume of coating work.

[Gordon]

Hi Schumi

Hi all,
I have been installing the air jets and researching a bit but I still have a similar problem.
The parameters I have used are the same that recomend the manufacturer of the powder:
-Oxigen: 3.4bar,flow 34
-Acetylene:1.3bar,flow 34
-Air (jets):4.8bar
-Spraying distance: 60mm
-Powder rate: 6 clicks open
-Point that the jets get crossed: 50mm
I am not sure if I could spray this material properly with this process but sulzer told me that I could.
I have some questions about the picture I have sent to gordon:
-What problem do you see with this?
-Do you think that I could get a good coating?
-How could I get the microhardness values for this? This is because the coating isn't dense enough to see the indenters trace.
I would appreciate a lot your help.
Thanks for all

"-What problem do you see with this? " Unfortunately, the metallographic sample preparation is not really allowing a true view of the ceramic coating, so it is difficult to comment.

"-Do you think that I could get a good coating?" Well this depends on what you define as a good coating. I have seen many "good" ceramic coatings produced by this gun, good as in the coatings performed well for there intended applications. If you are comparing to plasma, D-gun, HVOF ceramic coatings then no you can't expect same qualities.

"-How could I get the microhardness values for this? This is because the coating isn't dense enough to see the indenters trace." You will need to improve the metallographic preparation. Why do you want to do this test? To be honest I don't really see this as a good quality control test in this situation anyway.

[loriolo]

Hi Schumi
I think your parameters are not correct, because this material is usually applied on aero coatings with thermospray gun with very good results, are you sure you’ve been using the correct hardware for this kind of powder?, if no take as starting point the following parameters: Siphon pug 5P385 – Nozzle G – Meter Valve/powder feed rate 12/14 gr/min – Meter set valve 5-7 – Air cap with pinch position – Cross jet 50mm/5 bar – O2 2,3psi/ flow34 – C2H2 1,3bar/flow 34, if there are still problem, try reducing the powder feed rate.

[loriolo]

Hi Schumi
I think your parameters are not correct, because this material is usually applied on aero coatings with thermospray gun with very good results, are you sure you’ve been using the correct hardware for this kind of powder?, if no take as starting point the following parameters: Siphon pug 5P385 – Nozzle G – Meter Valve/powder feed rate 12/14 gr/min – Meter set valve 5-7 – Air cap with pinch position – Cross jet 50mm/5 bar – O2 2,3psi/ flow34 – C2H2 1,3bar/flow 34, if there are still problem, try reducing the powder feed rate.