Hardness test of the metco 314ns coating

[sam xu]

Hi,
I got some problems,recently when I sprayed the metco 314ns coating as usual(flame),the sample we tested could not reach the require value ,we have check the machine( by sulzer metco' engineer),and parameter,but no any change or any diffence.
we profrom a"rock well 15-y"hardness test to the sample,the repuire value is between 45 to 55, unfortunately,the result just reach 40.
parameter: acetylene 25L/min
Oxygen 28L/min
Distance form gun to part :200mm
gun type : sulzer metco 6p2
we try to change the parameter of the acetylece and oxygen's flow rate.the value became to aceept until the acetylene change to 35.but the coating seem to be very fragile and build up very slow.Anther change is the flame,it become stronger and longer than before,could anyone can help me to solve this problem,what is the suitable proportion
of acetylene and oxygen?
thank you so much.

[Gordon]

Hi sam xu

The normal recommendation for hardness correction when using OEM recommended parameters is: increasing acetylene flow to increase hardness and reducing flow to reduce hardness.

The standard parameters I have at hand for 314NS and 6P-II are:
Nozzle P 7C-M
Siphon Plug 6P 605
Air cap 6P 3 (air pressure 15psi)
Oxygen 40 flow @ 30psi (type 2GF flowmeter)
Acetylene 40 flow @ 12psi (type 2GF flowmeter)
Carrier gas 37 flow @55psi (3MP/4MP)
Spay distance 216mm
Spray rate 38-45 g/min

Not sure how that compares to your l/min.

Using standard recommended parameters should have you reasonably close to your desired hardness. Adjusting acetylene only for fine tuning.

[ServiceTech]

Ensure the coating surface is lightly sanded after spraying in order to "knock off the corn flakes", otherwise you will see an erroneous reading.

[Gordon]

"knock off the corn flakes" not heard that expression before.

Hopefully, all recommended abradable coating HR15Y hardness testing procedures are followed correctly, otherwise we will all be "led up the garden path"

[ServiceTech]

I like a little humor mixed in once in awhile Gordon :^)

Too many times over the years I've been "led up the garden path"!

[sam xu]

Hi，Gordon,
Firstly thank you for your honest reply,I have check my parameters after read your message, there are someting I can not understand,
1, is it your oxygen and acetylene's flow reading form the flowmeter 2GF and 3GF ?what is the units of them?
2 from the chemical equation 2C2H2+5O2=2H2O+4CO2 we can see, the oxygen and acetylence could be burned completely by the proportion of 2:5.in my pramater the acetylence is too more compare with oxygen ,that means there exist a few flow of acetylence have not burn or could not burn completely,is it reasonable?
Thank you very much.

[Gordon]

Hi sam xu

1, is it your oxygen and acetylene's flow reading form the flowmeter 2GF and 3GF ?what is the units of them?

How do you measure flows?

The flows I quoted are for the Metco 2GF flow meter, which are just an arbitrary Metco flow meter reading (most Metco parameters are still based on these). To convert to a more recognised flow unit like SCFH or NLPM requires calculation along with specific details such as temperature and pressure. Its a bit late now and I don't have info to hand, but I could work them out for you if needed at a later time. 3GF flow meters I believe give direct read outs in SCFH and NLPM when set to recommended pressures.

2 from the chemical equation 2C2H2+5O2=2H2O+4CO2 we can see, the oxygen and acetylence could be burned completely by the proportion of 2:5.in my pramater the acetylence is too more compare with oxygen ,that means there exist a few flow of acetylence have not burn or could not burn completely,is it reasonable?

A neutral or normal oxygen/acetylene flame only requires about 43% of the stoichiometric oxygen requirement. Highest flame temperature occurs at about 60%. So the answer to your question is yes