Ceramic Coating on Aluminum Base metal

[demionkrishan]

Hi all,
So far i never used to spray HVOF / Plasma coating on Aluminum base material.
is there anybody can help me regarding this?
will HVOF / Plasma process work on aluminum base material?
what type of powders can use for wear resistance on Aluminum base?
melting point of aluminum will be around 600C, is this process will damage the
component during spray?

Please share your experience, Thank you all in advance

Regards
Krishan

[Vadim Verlotski]

Hi all,
So far i never used to spray HVOF / Plasma coating on Aluminum base material.
is there anybody can help me regarding this?
will HVOF / Plasma process work on aluminum base material?
what type of powders can use for wear resistance on Aluminum base?
melting point of aluminum will be around 600C, is this process will damage the
component during spray?

Please share your experience, Thank you all in advance

Regards
Krishan

Hi Krishan,

Coating on aluminum substrates is no problem at all. The adhesion of ceramic layers is sometimes even better in comparison with the coating on steel. Even large layer thicknesses are possible. You just have to be careful that your component does not get too hot during coating (low single pass thicknesses and good cooling).
Of course, this is only about the applications at room temperature (up to about 300°C).

Regards
Vadim

[Lemster68]

Vadim, what is your opinion of preheating for an Aluminum substrate? Very minimal preheat or none at all? I am asking because I am concerned about oxidation on the Aluminum.

[Vadim Verlotski]

Vadim, what is your opinion of preheating for an Aluminum substrate? Very minimal preheat or none at all? I am asking because I am concerned about oxidation on the Aluminum.

We coat aluminum without preheating, although preheating to max. 200-250°C would also be possible.

[Lemster68]

Vadim, what is your opinion of preheating for an Aluminum substrate? Very minimal preheat or none at all? I am asking because I am concerned about oxidation on the Aluminum.

We coat aluminum without preheating, although preheating to max. 200-250°C would also be possible.

Thank you Vadim!

[DMan]

Dear Sir

How many micron per pass should we coat Cr203 on aluminium considering i cant cool the base .
Is a bond coat advisable in the spray process .
I get a white patchy surface in aluminium once i start diamond grinding the material.
Kindly advise.

Hi all,
So far i never used to spray HVOF / Plasma coating on Aluminum base material.
is there anybody can help me regarding this?
will HVOF / Plasma process work on aluminum base material?
what type of powders can use for wear resistance on Aluminum base?
melting point of aluminum will be around 600C, is this process will damage the
component during spray?

Please share your experience, Thank you all in advance

Regards
Krishan

Hi Krishan,

Coating on aluminum substrates is no problem at all. The adhesion of ceramic layers is sometimes even better in comparison with the coating on steel. Even large layer thicknesses are possible. You just have to be careful that your component does not get too hot during coating (low single pass thicknesses and good cooling).
Of course, this is only about the applications at room temperature (up to about 300°C).

Regards
Vadim

[Vadim Verlotski]

Dear DMan

The problem with white patchy surface in aluminum once your start diamond grinding the material is associated with incorrect sandblasting before coating: your aluminum surface before spraying is too rough, which results in an extremely rough layer. During grinding, you simply take away too much layer material to get a smooth surface. After grinding such a rough coating, you will see the tips of rough base material or the metallic bond coat (white dots).

The solution to this problem is very simple, you should use finer corundum for sandblasting: grit 90 or even 120. There is a general rule: the softer the base material, the finer the sandblasting material should be. The explanation for this is also obvious: the same sand particles create a rougher surface in a soft material than in a hard one. For this reason, corundum grain 22 was acceptable for steel rolls, but not for aluminum rolls.

Regards
Vadim

[DMan]

Dear Vadim
Thanks for the help .
We use aluminium oxide grit 22 for blasting the surface.
As suggested by you I will try to change it to 90-120.
what should be the blasting pressure I have to maintain ?right now its upto 3-4 bars.
Can anything be related to the coating thickness of Cr2o3 i am maintaining.I coat around 60 microns per pass top coat and coat 350 microns in total on both MS and AL.

Dear DMan

The problem with white patchy surface in aluminum once your start diamond grinding the material is associated with incorrect sandblasting before coating: your aluminum surface before spraying is too rough, which results in an extremely rough layer. During grinding, you simply take away too much layer material to get a smooth surface. After grinding such a rough coating, you will see the tips of rough base material or the metallic bond coat (white dots).

The solution to this problem is very simple, you should use finer corundum for sandblasting: grit 90 or even 120. There is a general rule: the softer the base material, the finer the sandblasting material should be. The explanation for this is also obvious: the same sand particles create a rougher surface in a soft material than in a hard one. For this reason, corundum grain 22 was acceptable for steel rolls, but not for aluminum rolls.

Regards
Vadim

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[Vadim Verlotski]

Dear DMan,

Pressure of 3-4 bar when sandblasting is a little too low, but it works. 4-6 bar is rated as "normal".

60 microns per pass is far too much! I cannot recommend a layer thickness per pass over 10 microns for any coating materials, but for ceramics it should even be under 5-6 microns per pass.

Regards
Vadim

[DMan]

Dear Vadim

Thanks for your help and useful information.
Will get back to you shortly.

Dear DMan,

Pressure of 3-4 bar when sandblasting is a little too low, but it works. 4-6 bar is rated as "normal".

60 microns per pass is far too much! I cannot recommend a layer thickness per pass over 10 microns for any coating materials, but for ceramics it should even be under 5-6 microns per pass.

Regards
Vadim

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