04-01-2010, 12:32 PM,
|
|
bepsi
Junior Member
|
Posts: 4
Threads: 2
Joined: Apr 2010
Reputation:
0
| |
How to decide grit size ?
Hello forum members,
I'm currently trying to plasma spray T400 & T800 onto Ni-based alloy substrate, and come across this problem.
Although GE specification P16TF5 mentioned the substrate has to be roughened by grit blasting to 80-150 Ra prior to coating, it didn't give the information of how the grit size should be decided. I did find specification D50TF5, which stipulated the grit composiion, but still, it didn't specify what grit size shall be applied in a specific situation.
So I just wondered, is there a GE specification which could answer my question? Or whatever the grit size I chose, it's just OK as long as I could obtain the required roughness defined by specification?
Does anyone have any suggetion?
Thanks a lot.
|
|
04-05-2010, 03:33 AM,
|
|
ykang
Active Member
|
Posts: 31
Threads: 10
Joined: May 2008
Reputation:
2
| |
RE: How to decide grit size ?
Quote:Or whatever the grit size I chose, it's just OK as long as I could obtain the required roughness defined by specification?
For my understanding, it is true with your statement. I am using Mesh#60. Never see any spec to restrict the used grit size, unless there is a call-out in blue print.
For GE spec, personally I think it is more concern with the interface contamination rather than the roughness (of course you have to meet the min requirement, 80 Ra uin), so you have to consider what grit size you wish to use.
Too fine -> take long blasting time to give required roughness -> might give high contamination.
Too course -> also may encounter interface problem with big embedded media.
However, there are many factors to decide the final roughness reading, i.e. distance, pressure, volumetric flow, hardness of media..... you need to experiment it to establish your own matrix.
|
|
04-29-2011, 03:14 AM,
|
|
ServiceTech
Senior Member
|
Posts: 58
Threads: 5
Joined: Feb 2011
Reputation:
3
| |
RE: How to decide grit size ?
Reference GE SPM 70-49-00 which specifies the use of 60 mesh AlO2 grit and allows coarser grit size only if using mechanical work handling.
(04-01-2010, 12:32 PM)bepsi Wrote: Hello forum members,
I'm currently trying to plasma spray T400 & T800 onto Ni-based alloy substrate, and come across this problem.
Although GE specification P16TF5 mentioned the substrate has to be roughened by grit blasting to 80-150 Ra prior to coating, it didn't give the information of how the grit size should be decided. I did find specification D50TF5, which stipulated the grit composiion, but still, it didn't specify what grit size shall be applied in a specific situation.
So I just wondered, is there a GE specification which could answer my question? Or whatever the grit size I chose, it's just OK as long as I could obtain the required roughness defined by specification?
Does anyone have any suggetion?
Thanks a lot.
|
|
04-29-2011, 05:56 AM,
(This post was last modified: 04-29-2011, 06:15 AM by wilfred1963.)
|
|
wilfred1963
Active Member
|
Posts: 23
Threads: 1
Joined: Jan 2011
Reputation:
2
| |
RE: How to decide grit size ?
36 grit works well for RA requirements as far as grit contamination try using a soft bristle brush after blast with high pressure air to remove excess from hardware have had repeatable results with 1/4 inch blast nozzle(ceramic) at 6 inch stand off
with 50 to 60 psi pressure at a 30-50 degrees deflection manual and automatic and being it's GE set a prescribed amount of git and usage time/pieces before grit change have done lots of GE hardware with plasma and hvof, they do love the full testing of all processes
Hey Gordan you asked me to let you know how things went with the WC-CO hardness that we chatted about a few months ago when i asked about parameters, hardness,and oxide stringers, sorry i didn't get in touch sooner but i was able to produce a coating (HVOF DJ8W) of 1190 to 1230 Dph (ten diamond drop) with Metco 2005NS repeatable with 4 different lots.carbide content was in the 28 to 40 % range, bond tinsel pulls 10500 Avg psi. with 10,000 being the min. and 11,000 being the high now here is the kicker went through all that to learn today that they now want to swap over to propylene for fuel gas.. go figure.. can some one please take me away???
|
|
|