Winter spray problems

[Bacon]

Hi everyone

Does anyone of you have problems during the colder month of the year? I work for a company in northern Canada that plasma spray chromium oxide with 100he gun and, between December and March, we always have problems like coating spitting, rough bond coat or coating pull-offs at the grinding step. Outside temperature varies between -35C and -5C.

Our powders are stored in a heated closet. Gases are outside but there are enough tubing inside the building that the gas temperature entering the mass flow meters stay near room temperature (20C)

Any ideas what to look for? Now we are testing smoother parameters at lower feed rate.

Thank you

Mike

[Vadim Verlotski]

(01-18-2018 03:41 PM)Bacon Wrote:  Hi everyone

Does anyone of you have problems during the colder month of the year? I work for a company in northern Canada that plasma spray chromium oxide with 100he gun and, between December and March, we always have problems like coating spitting, rough bond coat or coating pull-offs at the grinding step. Outside temperature varies between -35C and -5C.

Our powders are stored in a heated closet. Gases are outside but there are enough tubing inside the building that the gas temperature entering the mass flow meters stay near room temperature (20C)

Any ideas what to look for? Now we are testing smoother parameters at lower feed rate.

Thank you

Mike

Hi Bacon,
All these problems can be caused by water condensation on cold metallic surfaces. If your parts are not preheated before sandblasting, condensation may adversely affect adhesion (cold blasted surface tends to corrode). Condensation in powder containers and powder lines is equally dangerous, which can cause spitting.

[demionkrishan]

Try to increase chiller water temperature by another 10F. Usually it will be 60F make it as 70-75. Is your gun getting moisture during spray? If it so then, try to dry

[ThePlummer54]

Reduce argon flow and pressure a little

[DMan]

Dear All
I use plasma coating for Cr2O3 ceramic coating.
Argon and Hydrogen is the carrier gases used.
My argon is 99 % pure but is kept outside my building premise during rainy season and winters.
Do we need to take any precautionary measure for the argon gas bottles like a thermal jacket to maintain a steady temperature.
In winters the outside temp is going down to 10-14 degrees .

Similarly, what more preventive measures can i take other than powder preheating (during rainy seasons) so that i have a constant chemistry for the plasma and coating quality is not effected.

Await to hear you all
DMan