T400 plasma spray

[Bostick123]

Hi
Having trouble with F50TF32B, structure looks good but it wont stick to 6-4 TI, if i use INCO 718 the problem goes away, i've used the Metco 9mb and the SG100 gun and both produce the same results on TI. My tensiles are pulling 7,000 PSI on Inco 718 and my hardness is 85.6 15n Scale. is there any suggestion on this.

Ken

[Gordon]

Hi Ken

to the Surface Engineering Forum.

When you say "structure looks good but it wont stick to 6-4 TI" at what point does it fail?

What coating thickness are you trying to achieve?

What is the substrate preparation procedure prior to spraying? Are you getting problems with grit blasting debris retention on surface?

What is the preheat temperature and coating/part temperature during spraying? Also coating layer thickness per pass?

I will move this thread to surface engineering where I think it will be better suited.

[Bostick123]

Gordon,
Thanks for the RE.
The coating is failing at the Substrate, only applying .008 to .012 thick,
I was preheating the TI, and then i stopped, once i stop the preheat, the condition went away. i guess the TI was Oxidizing before the first coating pass. I'm using 60 grit Alum Oxide at 50 to 60 PSI, thickness per is .0004 to .0005 per pass, Now i have a slight unmelt problem that was present before, unmelts right on the border of failing, I've tryed everything with the current gun and had to drop down to a slower gun, to slow down the partical, i was using the Sg100 with the mach 2 package which gave me a good looking structure except the unmelts where to close. i went back to the subsonic package and now I'm fighting Delam again becasue of stress in the coating and trying to find away to get it out. I'm using the spray watch system to look at the flame and it is getting me closer to where i need to be. but the last 10% is always the hardest. and i still have a unmelt issue, it seems the Molly a melting point of 2600 C and everything else has a lower melting point and when i get the molly to melt i over heat the lower melting Alloys and i pull them out during grind. but the first problem seems to went away for now, now just fighting unmelts and delam from stress.

ken

Hi Ken

to the Surface Engineering Forum.

When you say "structure looks good but it wont stick to 6-4 TI" at what point does it fail?

What coating thickness are you trying to achieve?

What is the substrate preparation procedure prior to spraying? Are you getting problems with grit blasting debris retention on surface?

What is the preheat temperature and coating/part temperature during spraying? Also coating layer thickness per pass?

I will move this thread to surface engineering where I think it will be better suited.

[Gordon]

Hi Ken

Good to hear you are making progress

it seems the Molly a melting point of 2600 C and everything else has a lower melting point and when i get the molly to melt i over heat the lower melting Alloys and i pull them out during grind. but the first problem seems to went away for now, now just fighting unmelts and delam from stress.

I don't think molybdenum is in a non combined state in this powder - powder is alloyed not mechanically blended constituents. So everything should be molten after about 1600 C or so. To reduce unmelted particles first check that the powder injection into plasma is optimal (carrier gas flow, powder feed rate, powder port set-up). Assuming powder injection is ok, you will need to either increase plasma energy (thermally rather than kinetically) or reduce particle velocity (increase particle dwell time) by increasing secondary gas (or possible amps) or reducing primary gas flow or combination.

Delamination/stress problems may primarily be associated with controlling coating/substrate temperature.