About Hardness issue of PAC 6CO by Metco 9MB Gun
12-30-2008, 03:03 PM,
#1
About Hardness issue of PAC 6CO by Metco 9MB Gun
Hello everyone,

I'm a new member here. Really happy to know all of you.
Now we are coating the ST-6 wear coating (powder PAC 6CO) on Hula seal using Metco 9MB gun.
We tried both N2 and Ar as primary gas and H2 as secondary gas...different Amperes and Voltages...but we can't get required hardness (average 450 HV), normally we can get is from 300 HV to 430 HV...Sad
Could some experts can instruct how to get the high hardness? What's the key factors to get high hardness?

Thanks a lot!
Reply
12-30-2008, 05:36 PM,
#2
RE: About Hardness issue of PAC 6CO by Metco 9MB Gun
Hi Amanda

Sign0016 to the Surface Engineering Forum.

Sorry, no experience with PAC 6CO. A quick search only reveals that it primarily is designed for PTA (plasma transferred arc welding process).

The main factor in achieving the highest hardness for a specific material with plasma spraying is coating density. The higher the density (lower porosity) the higher (or more consistent) the hardness test reading.

Is the "required hardness (average 450 HV)" known to be achieved by plasma spray PAC 6CO or is it just the requirement for the coated part (not necessarily PAC 6CO). How is this hardness measured? - cross-section micro-hardness HV/0.3 or other? It may be that you are approaching the maximum achievable for plasma spray PAC 6CO, PTA coatings I would expect to be a little harder.

Can you use similar type coatings like T400, T800, Metco 45, Praxair Co-106, Stellite 6 etc. or are you bound by customer specification?
Reply
12-30-2008, 07:39 PM,
#3
RE: About Hardness issue of PAC 6CO by Metco 9MB Gun
(12-30-2008, 03:03 PM)Amanda Wrote: Hello everyone,

I'm a new member here. Really happy to know all of you.
Now we are coating the ST-6 wear coating (powder PAC 6CO) on Hula seal using Metco 9MB gun.
We tried both N2 and Ar as primary gas and H2 as secondary gas...different Amperes and Voltages...but we can't get required hardness (average 450 HV), normally we can get is from 300 HV to 430 HV...Sad
Could some experts can instruct how to get the high hardness? What's the key factors to get high hardness?

Thanks a lot!

Hi Amanda,

(links dead)

PAC Cobalt Base 6Co A coblat base chromium tungsten alloy suitable for high temperature corrosion and oxidation resistant applications by requiring moderate impact with slightly less wear resistance than PAC 1Co

RC 35-40 ?345�392 HV

Ion
Reply
12-31-2008, 02:31 AM, (This post was last modified: 12-31-2008, 02:37 AM by Amanda.)
#4
RE: About Hardness issue of PAC 6CO by Metco 9MB Gun
(12-30-2008, 05:36 PM)Gordon Wrote: Hi Amanda

Sign0016 to the Surface Engineering Forum.

Sorry, no experience with PAC 6CO. A quick search only reveals that it primarily is designed for PTA (plasma transferred arc welding process).

The main factor in achieving the highest hardness for a specific material with plasma spraying is coating density. The higher the density (lower porosity) the higher (or more consistent) the hardness test reading.

Is the "required hardness (average 450 HV)" known to be achieved by plasma spray PAC 6CO or is it just the requirement for the coated part (not necessarily PAC 6CO). How is this hardness measured? - cross-section micro-hardness HV/0.3 or other? It may be that you are approaching the maximum achievable for plasma spray PAC 6CO, PTA coatings I would expect to be a little harder.

Can you use similar type coatings like T400, T800, Metco 45, Praxair Co-106, Stellite 6 etc. or are you bound by customer specification?

Hi Gordon,

Thanks a lot for your quick response! We use cross-section micro-hardness HV/0.3 to measure the hardness. The 450HV was required by customer's coating specification...also plasma spray was required by customer's spec. And I know that some other vendors can achieve the hardness requirement by using this kind of powder.
You are right! We use HVOF with high density for some Stellite 6 coating and no hardness issue...
How to get higher density by plasma coating? Higher primary gas pressure and flow? the spraying distance? powder feed rate? or other?
I was told that more oxide content will also get higher hardness, and we tried 600A and DCV 84V with G nozzle and 9MB 63 electrode...but the nozzle was burnt only after a few times of coating, what's your suggestion about increase energy level by using 9MB gun?

Thanks!
Amanda
(12-30-2008, 07:39 PM)plasmajet1990 Wrote:
(12-30-2008, 03:03 PM)Amanda Wrote: Hello everyone,

I'm a new member here. Really happy to know all of you.
Now we are coating the ST-6 wear coating (powder PAC 6CO) on Hula seal using Metco 9MB gun.
We tried both N2 and Ar as primary gas and H2 as secondary gas...different Amperes and Voltages...but we can't get required hardness (average 450 HV), normally we can get is from 300 HV to 430 HV...Sad
Could some experts can instruct how to get the high hardness? What's the key factors to get high hardness?

Thanks a lot!

Hi Amanda,

(links dead)

PAC Cobalt Base 6Co A coblat base chromium tungsten alloy suitable for high temperature corrosion and oxidation resistant applications by requiring moderate impact with slightly less wear resistance than PAC 1Co

RC 35-40 ?345�392 HV

Ion

Hi Ion,

Thanks for your prompt response! You mean 345~392 HV is the highest hardness which PAC6 Co can achieve?

Thank you very much!
Amanda
Reply
12-31-2008, 05:06 AM,
#5
RE: About Hardness issue of PAC 6CO by Metco 9MB Gun
Hi Ion

Thanks for your input. Happy0193 funny enough that's the first link i came across. Though, that is for PTA, which I would have thought would give higher hardness than plasma spray Question although, converting from HRC to cross-sectional micro-hardness HV/0.3 is very very shall we say hit and miss. Though I think 450+ HV/0.3 may be a hard target to meet consistently.

Hi Amanda

Quote:You are right! We use HVOF with high density for some Stellite 6 coating and no hardness issue...
How to get higher density by plasma coating? Higher primary gas pressure and flow? the spraying distance? powder feed rate? or other?
Sad Difficult to know without being in your shoes and knowing what your base line parameters and equipment etc.

Quote:I was told that more oxide content will also get higher hardness, and we tried 600A and DCV 84V with G nozzle and 9MB 63 electrode...but the nozzle was burnt only after a few times of coating, what's your suggestion about increase energy level by using 9MB gun?
Yes, sometimes higher oxide or higher temperature processing can yield higher hardness. Though, simple using higher energy plasma does not always give these conditions, it is a case of balance between thermal energy and velocity (and of course hardware life and deposit efficiency if cost efficiency is important Smile. What results do you get or would you get from say:

from Ar/H2 GE (731) nozzle, 400-500 A, 65-70 V, 100 Ar @ 75 psi/15 H2 @ 50 psi flows (old Metco FMR), spray rate 7 lb/hr @ 37 carrier gas flow (old FMR for 3MP,4MP etc.), spray distance 5" (~125 mm).
or
from N2/H2 G (730) nozzle, 400 - 500 A, 70-80 V, 100 N2/15 H2 flows (old Metco FMR @ 50 psi), Spray rate 15 lb/hr @ 37 carrier gas flow (old FMR for 3MP,4MP etc.), spray distance 5" (~125 mm). (possibly better deposit efficiency and possible hardness).

These are based on parameters for Metco 45-Ns, which I would consider as a good starting point for parameter development for your powder, though not necessarily the best Happy0193, but at least with hardness and good metallography results, it forms a good base in which I could make suggestions for further action.
Reply
01-04-2009, 03:56 AM, (This post was last modified: 01-04-2009, 04:09 AM by Amanda.)
#6
RE: About Hardness issue of PAC 6CO by Metco 9MB Gun
(12-31-2008, 05:06 AM)Gordon Wrote: Yes, sometimes higher oxide or higher temperature processing can yield higher hardness. Though, simple using higher energy plasma does not always give these conditions, it is a case of balance between thermal energy and velocity (and of course hardware life and deposit efficiency if cost efficiency is important Smile. What results do you get or would you get from say:
from Ar/H2 GE (731) nozzle, 400-500 A, 65-70 V, 100 Ar @ 75 psi/15 H2 @ 50 psi flows (old Metco FMR), spray rate 7 lb/hr @ 37 carrier gas flow (old FMR for 3MP,4MP etc.), spray distance 5" (~125 mm).
or
from N2/H2 G (730) nozzle, 400 - 500 A, 70-80 V, 100 N2/15 H2 flows (old Metco FMR @ 50 psi), Spray rate 15 lb/hr @ 37 carrier gas flow (old FMR for 3MP,4MP etc.), spray distance 5" (~125 mm). (possibly better deposit efficiency and possible hardness).

These are based on parameters for Metco 45-Ns, which I would consider as a good starting point for parameter development for your powder, though not necessarily the best Happy0193, but at least with hardness and good metallography results, it forms a good base in which I could make suggestions for further action.

Hi, Gordon~
Happy New Year~Ashamed0002~
from Ar/H2 we tried these parameters:
GE (732) nozzle, 500 A, 74 V, 150 Ar @ 75 psi/15 H2 @ 50 psi flows (old Metco FMR), spray rate 6 lb/hr @ 30 carrier gas flow (old FMR for 4MP etc.), spray distance 4" (~125 mm).

from N2/H2:
GH/732 nozzle, 500 A, 72V, 150 N2/15 H2 flows (old Metco FMR @ 50 psi), Spray rate 15 lb/hr @ 40 carrier gas flow (old FMR for 4MP.), spray distance 4" (~125 mm)...and some parameters around this group, like raise AC&Voltage meanwhile reduce powder feed rate to enhance power,etc. But it seems no obvious improvement on hardness(still below 400hv on average).

Just as you said that N2 as primary gas seems melt powder better than Ar. I wonder why?
And is there any suggestions about spareparts?

Sincerely thanks for your great help~

Amanda
Reply
01-05-2009, 12:38 PM,
#7
RE: About Hardness issue of PAC 6CO by Metco 9MB Gun
Hi Amanda

First, I will apologies for making a typo, nozzle GE equivalent 9MB tap nozzle is 731 not 732 (GH equivalent) and G nozzle is 730 not 731 Ashamed0002 I will edit post above to read correct.

Quote:Just as you said that N2 as primary gas seems melt powder better than Ar. I wonder why?

Well, this really depends more on the parameters you set. Nitrogen plasma though can have the greater heating effect even though its plasma temperature is lower than that of argon. Nitrogen is a diatomic molecule, so in forming a plasma has to undergo dissociation to atomic form before ionisation. Large amounts of latent heat are involved in both these changes of state. Argon on the other hand is monatomic, so it only has one state change of ionisation to form a plasma. See plasma flame theory for more info.

Quote:from N2/H2:
GH/732 nozzle, 500 A, 72V, 150 N2/15 H2 flows (old Metco FMR @ 50 psi), Spray rate 15 lb/hr @ 40 carrier gas flow (old FMR for 4MP.), spray distance 4" (~125 mm)...and some parameters around this group, like raise AC&Voltage meanwhile reduce powder feed rate to enhance power,etc. But it seems no obvious improvement on hardness(still below 400hv on average).

GH/732 nozzle? If so I would recommend changing to a G/730 nozzle.

Lower primary gas flows i.e. 100 instead of 150 should provide extra particle heating (lower velocity, longer dwell time for particles). Though I would let metallography results (balance of porosity,unmelts, oxides etc.) guide me on parameter change direction rather than just hardness results.

I would suspect Ar/h2 parameters will give the "better coating" in terms of density, lower oxide and will be kinder to nozzle and electrode. N2/H2 I think may give a harder coating, with more oxide and will be bit more erosive on hardware (though cheaper process gas and better deposit efficiency).
Reply
01-23-2009, 05:01 AM, (This post was last modified: 01-23-2009, 10:50 AM by Amanda.)
#8
RE: About Hardness issue of PAC 6CO by Metco 9MB Gun
(01-05-2009, 12:38 PM)Gordon Wrote: Hi Amanda

First, I will apologies for making a typo, nozzle GE equivalent 9MB tap nozzle is 731 not 732 (GH equivalent) and G nozzle is 730 not 731 Ashamed0002 I will edit post above to read correct.

Quote:Just as you said that N2 as primary gas seems melt powder better than Ar. I wonder why?

Well, this really depends more on the parameters you set. Nitrogen plasma though can have the greater heating effect even though its plasma temperature is lower than that of argon. Nitrogen is a diatomic molecule, so in forming a plasma has to undergo dissociation to atomic form before ionisation. Large amounts of latent heat are involved in both these changes of state. Argon on the other hand is monatomic, so it only has one state change of ionisation to form a plasma. See plasma flame theory for more info.

Quote:from N2/H2:
GH/732 nozzle, 500 A, 72V, 150 N2/15 H2 flows (old Metco FMR @ 50 psi), Spray rate 15 lb/hr @ 40 carrier gas flow (old FMR for 4MP.), spray distance 4" (~125 mm)...and some parameters around this group, like raise AC&Voltage meanwhile reduce powder feed rate to enhance power,etc. But it seems no obvious improvement on hardness(still below 400hv on average).

GH/732 nozzle? If so I would recommend changing to a G/730 nozzle.

Lower primary gas flows i.e. 100 instead of 150 should provide extra particle heating (lower velocity, longer dwell time for particles). Though I would let metallography results (balance of porosity,unmelts, oxides etc.) guide me on parameter change direction rather than just hardness results.

I would suspect Ar/h2 parameters will give the "better coating" in terms of density, lower oxide and will be kinder to nozzle and electrode. N2/H2 I think may give a harder coating, with more oxide and will be bit more erosive on hardware (though cheaper process gas and better deposit efficiency).

Hi, Gordon,Ashamed0002

How you doing these days? Thanks a lot for your information~
Resently we went on to try on promoting this kind of coating hardness. Lots of groups parameters has been applied but still no evidence on a big hardness improvement.
now I'm suspecting that if we vickers microhardness test method has problems. Do you know that how much force shall we select to test around thickness 0.018" hardface and Cobalt Based coating normally?
Documents suggested to use 300gf force but I'm not sure if it's reasonable for such a thin coating.
I'm confusedSad
Reply
01-26-2009, 04:32 PM,
#9
RE: About Hardness issue of PAC 6CO by Metco 9MB Gun
Hi Amanda

Quote:now I'm suspecting that if we vickers microhardness test method has problems. Do you know that how much force shall we select to test around thickness 0.018" hardface and Cobalt Based coating normally?
Documents suggested to use 300gf force but I'm not sure if it's reasonable for such a thin coating.
I'm confusedSad

300gf force or HV/0.3 is pretty standard for coating cross-section hardness testing. 0.018" (~0.45 mm) coating thickness with support from substrate and mounting medium should give you plenty of space. The distance between the centre of any indentation and any edge of the test piece or edge of another indentation should not be less than 2.5 times the diagonal of the indentation. Diagonal for 450HV/0.3 around 0.035 mm so keeping towards mid thickness distance will keep you well within recommendation Smile

I suggest you try HV/1 and compare results with HV/0.3. Usually HV/1 will give a lower reading than HV/0.3, but is easier to measure and less error prone. If you get higher readings, then suspect the reading accuracy at HV/0.3.

I can't help but think you are already reaching the upper hardness limits for this coating.
Reply
02-01-2009, 07:13 AM,
#10
RE: About Hardness issue of PAC 6CO by Metco 9MB Gun
(01-26-2009, 04:32 PM)Gordon Wrote: Hi Amanda

300gf force or HV/0.3 is pretty standard for coating cross-section hardness testing. 0.018" (~0.45 mm) coating thickness with support from substrate and mounting medium should give you plenty of space. The distance between the centre of any indentation and any edge of the test piece or edge of another indentation should not be less than 2.5 times the diagonal of the indentation. Diagonal for 450HV/0.3 around 0.035 mm so keeping towards mid thickness distance will keep you well within recommendation Smile

I suggest you try HV/1 and compare results with HV/0.3. Usually HV/1 will give a lower reading than HV/0.3, but is easier to measure and less error prone. If you get higher readings, then suspect the reading accuracy at HV/0.3.

I can't help but think you are already reaching the upper hardness limits for this coating.

Hi, Gordon,
Yes we followed your suggestion but microhardness of HV/1 nearly the same as HV/0.3Sad
Maybe you're right, I searched this kind of powder on net that it's typical hardness is 40HRC. but some other plants use this powder and 9MB gun to make this coating hardness up to more than 500, it's really strange..
It was really a big challenge..

Anyway, Sincerely thanks for your kindhearted help and professional information. I've learnt a lot from you.Smile

Thanks a lot..
Reply
02-02-2009, 11:35 AM,
#11
RE: About Hardness issue of PAC 6CO by Metco 9MB Gun
Have you spoken to your local Deloro Stellite agent? I know that Deloro used to change the carbon content of some of the Stellite powders to either increase or decrease the hardness. Stellite 6 (40-46Hrc), Stellite 6LC (38-44Hrc) or Stellite 6HC (43-53Hrc). What is the carbon content of the powder you are using?
Reply
02-03-2009, 02:15 AM,
#12
RE: About Hardness issue of PAC 6CO by Metco 9MB Gun
(02-02-2009, 11:35 AM)adam wintle Wrote: Have you spoken to your local Deloro Stellite agent? I know that Deloro used to change the carbon content of some of the Stellite powders to either increase or decrease the hardness. Stellite 6 (40-46Hrc), Stellite 6LC (38-44Hrc) or Stellite 6HC (43-53Hrc). What is the carbon content of the powder you are using?

Hello, adam wintle,

Thanks for ur response~Smile
The C content stellite 6 powder we used is 1.15%,and the PAC 6CO powder is 0.98%
I searched on there offical .com that the Stellite 6 HRC is 40~46 just as you said, and the PAC 6CO HRC is 40 typically.
All of them were tested at the same coating parameters but the microhardness result seems no abvious difference..
What is your suggestion? Have u ever used these kinds of powders?
Reply
02-03-2009, 12:39 PM,
#13
RE: About Hardness issue of PAC 6CO by Metco 9MB Gun
No, I only sell the powders for Deloro. Contact them through their website or let me know what area you are in and your e-mail address and I will see what I can do.
Reply




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