Erosion Test of an Abradable Coating
02-10-2014, 10:25 AM,
Erosion Test of an Abradable Coating
Dear All,
We are spraying 60:40 Ni/Graphite over Metco 450NS via flame spraying. Top coat thickness is within .060-.070". As you know this powder combination is an abradable coating and there is an erosion test reqirement which I should verify and we couldn’t have managed so far. My question is about this requirement.
The erosion rate requirement is in terms of sec/mil (max 9 sec/mil) but, I am a little bit over that requirement (11 sec/mil). I suppose I can lower this value by decreasing hardness (Hardness checks 70 HR15Y). Is this correct?
*Erosion rate: time to deplete a specific amount of grit media/depth of erosion
Technical Info:
We’re using a 6P-II gun with a 6PT-II-1 extension module and spraying at an angle of 80 degrees. System consists of oxygen, acetylene and Argon as carrier gas.
I can not change pressure values due to possible risk of alterations at other coatings. Flow values are as follows (nlpm):
-Oxygen: 14
-Acetlyene: 14
-Argon: 3.5
Spray rate: 55 gr/sec
Would you please advice if I should increase the spray rate or change the flow values? Or any other ideas?
Thank you very much.
02-10-2014, 02:50 PM,
RE: Erosion Test of an Abradable Coating
Hi baaddin

Sign0016 to the Surface Engineering Forum.

Change oxygen and fuel gas flows equally. Decreasing flow will make coating softer. Keep all other parameters constant. A HR15Y hardness of around 50 should give you the desired result.

02-10-2014, 08:50 PM,
RE: Erosion Test of an Abradable Coating
Look for what I call spider webbing between the nickel in the microstructure. It is a good indication of your temperature and it greatly affects the erosivity. No spider webbing and you get a low erosivity value high spider webbing you get a high value. Drop the temperature until less spider webbing is present and then chech the erosivity value.
02-11-2014, 07:32 AM,
RE: Erosion Test of an Abradable Coating
Thank you all for the recommendations. I'm going to start the trials today and will share the results.

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