Poor Flame
12-17-2008, 05:00 PM,
#1
Poor Flame
Hi Guys,

We are trying to spray some Metco 58NS through our 3MB but not having much joySad We getting an unacceptabel level of oxides.
The flame doesn't look right but I'm not sure how to adjust it. The flame seems to be split into 2 pieces with the main section pointing down a little. We have played with the carrier gas, going from 3 lpm to 8 but this does not move the flame as I would expect. There is also what looks like unmelted powder to the top of the flame.
Any suggestions as to where we should be looking or is this the expected flame pattern given this particular powder (we haven't sprayed this before)?

Roll on Christmas!!

Thanks

Jim


Attached Files
.pdf   flame.pdf (Size: 9.97 KB / Downloads: 322)
Reply
12-17-2008, 05:18 PM,
#2
RE: Poor Flame
Hi Jim

Could you let us know the spray parameters used?
Reply
12-17-2008, 07:21 PM,
#3
RE: Poor Flame
Hi Gordon,

Certainly, we are running the following parameters;
Argon 36.6 nlmp
Hydrogen 7 nlmp
500 amp
Achieving around 62 volt
All Metco recommended settings.

Carrier gas is Agron at 4.3 nlpm and the wheel set to 14 rpm to give the required 45gram/min deposit rate.

We stipped the gun and rebuilt it with new parts, renewed the powder feed and rebuild the hopper with NL suction/spreaders(we tried L type too but these were no better).

The flame is constant and not plusing.

Thanks
Jim
Reply
12-18-2008, 03:47 AM,
#4
RE: Poor Flame
Hi Jim

Those parameters should give you the desired coating. When you say excessive oxide, is this a judgement from your lab based on comparative photomicrographs or similar? Oxides should be around 1% or less typically for these parameters. Sorry, I always question lab results first, before I start chasing may tail Happy0193

I assume you are using crossed air jets (crossed @ 4.5" with 40 psi). This may be why you are seeing a split spray stream when the gun is spraying off the job. Are you traversing a rotating work piece or ladder scan? Are the air jets set in a vertical or horizontal plane or should I say in-line or perpendicular to axis of rotating part or in direction of gun movement when ladder scanning?

4.3 NLPM argon carrier gas sounds a bit on the low side to me. Is that what Sulzer recommend? Metco old flow meter readings usually 37 in old money Happy0193, which should be roughly 6 - 7 NLPM based on 100 psi. I would check this out.

I would not deviate away from standard parameters unless all other options fail. In this case I would consider increasing argon primary gas flow a little say by 2.5 - 5 nlpm, this should increase the plasma energy a tiny bit (slight rise in voltage) but will in fact have a slight cooling effect on particles because of higher velocity. Be careful though, as oxides may reduce, unmelts may increase. Alternately, you could just reduce secondary hydrogen, but you seem to already be on the lower end of the 60 -70V range, so my preference would be increasing primary gas.
Reply
12-18-2008, 05:35 PM,
#5
RE: Poor Flame
Hi Gordon,

Smile Our lab man wasn't to impressed with your comment, cost me a cup a coffee that!

Well we've had a few other issues to deal with today but we managed to get a couple of test pieces sprayed. We upped the Argon to 41 nlpm and it does seem to have reduce the oxides and oxide clusters without introducing too many unmelts into the coating. Out last sample completely delaminated so first job of the day is to spray some more 58 onto a 450 base and have a proper look. I'll keep you posted

Thanks,
Jim
Reply




Possibly Related Threads…
Thread Author Replies Views Last Post
  Poor flame with Ni-based metallic powder - HVOF process Roy 2 2,995 02-26-2016, 12:30 AM
Last Post: Roy
  Poor integrity and oxides in Metco450NS DUYGU 6 4,872 11-24-2014, 01:49 PM
Last Post: DUYGU



Users browsing this thread: 1 Guest(s)





Surface Engineering Forum Sponsor - Alphatek Hyperformance Coatings Ltd