5pII chromium oxide coating

[ehsan]

Hi Dear
I have 5pII gun and i coated chromium oxide with this.but i have several problems.i done that coating with this parameters:
1-pressure of acetylen 2.5 bar oxygen 2.3bar
2-distance 65 mm
3-Ni-Al band coat
but i don,t know why in one cycle of spraying i get a good deposition but in another one i can not take any deposition without any parameters changing.
is this parameters is best or not?
what is the best parameters for best deposition and coating quality.
i should say that i think when i increase the temp of substrates more than 150 C condition was better but i am not sure.

[Gordon]

hi ehsan

to the Surface Engineering Forum.

May I ask which chromium oxide powder product are you using?

[ehsan]

Dear Gordon
Thanks for your reply.
I use Cr2O3 powder with -45/+20 size from GTV gmbh(germany company).
Regards
Ehsan

[Gordon]

Hi Ehsan

1-pressure of acetylen 2.5 bar oxygen 2.3bar

Is this correct?

If so, PLEASE STOP! It is not safe and dangerous to run acetylene at this pressure (2.5 bar or 36 psi). 1 bar or 15 psi is all you should need at most.

Your powder will be similar to Metco 106F and I would recommend using the parameters for that from the 5P-II Thermospray Gun Instruction Manual for your gun at least as a starting point. You will need 2PSA air jet assembly and under this section of the manual you will find parameters.

With chromium oxide powders of this type you will be lucky to see a deposit efficiency of 20% so don't expect to see rapid coating build-up.

[ehsan]

hi gordon
you said that i need 2PSA compressed air what is the meaning of PSA!!
ok i will chek again with this general manual but i increase the pressure because for chromium oxide i need more temprature for flame.
general parameters is:
acetylen 1.1 bar and oxygen 2.1 is it ok?
Ehsan

[Gordon]

Hi Ehsan

hi gordon
you said that i need 2PSA compressed air what is the meaning of PSA!!
ok i will chek again with this general manual but i increase the pressure because for chromium oxide i need more temprature for flame.
general parameters is:
acetylen 1.1 bar and oxygen 2.1 is it ok?
Ehsan

2PSA is part number of air jet assembly needed. You will need to set cross jets to 50 mm and use spray distance of 65 mm. Run with air pressure of 4.8 bar.

Use acetylene @ 1 bar and oxygen @ 1.7 bar. Refer to manual for other parameters as there are two nozzles that can be used - standard P7B-G and high spray rate P7C-K which use slightly different flows and spray rates.