Hardness Inconsistent

[rhortonaz]

Hello I am new to this forum and in dire need of some help.

I am based out of Chandler arizona where it seems that the summer months wreck havoc on my ability to register a good hardness test.

I am running a 6P-2 gun with the Durabrade 2222 powder.

We can run the same settings day to day even shift to shift and end up with a hardness ranging anywhere from 62 to 22.

My requirement is 50 +/- 10.

We have tried to modify our gas pressures and flows so far the only thing that has helped to keep us in the low 40's to to crank out Acetylene flow to 15psi, which has my Maintenance manager worried because of the danger of sucking acetone into the lines.

Ideally we should be at 10-12 psi.

Any ideas?

Thanks

[Gordon]

Hi Rhortonaz

to the Surface Engineering Forum.

Durabrade 2222 powder I think is pretty much the same as Metco 307. For the 6P-II gun and Metco 307 powder it is recommended that to adjust coating hardness:
* increase powder feed rate to reduce hardness
* reduce powder feed rate to increase hardness
keeping all the other parameters unchanged.

Hope that helps

[rhortonaz]

Thanks, That is usually the first thing we try,
then if that doesnt work you start to adjust the pressures and flows.
The funny thing is this only happens in the summer months where the humidity gets at or above 30%.
Any other time of the year we can run for ever and never run into a hardness problem.

Hi Rhortonaz

to the Surface Engineering Forum.

Durabrade 2222 powder I think is pretty much the same as Metco 307. For the 6P-II gun and Metco 307 powder it is recommended that to adjust coating hardness:
* increase powder feed rate to reduce hardness
* reduce powder feed rate to increase hardness
keeping all the other parameters unchanged.

Hope that helps

[Gordon]

Hi Rhortonaz

Can't quite see how the change in seasons or weather will have any significant effect on the process. Powder changes from batch to batch would probably be much more significant.

Looking through my old nickel graphite powders technical bulletin, I see typical hardness is 40 HR15Y +or- 10 for 307NS* (75Ni/25C) coatings which I think is pretty much the same stuff as Durabrade 2222. While 309NS-3 (80Ni/20C) typical hardness is 50 +or- 10. It may be that you are chasing the top end of the hardness capabilities of this powder

[erick212]

make sure you keep your powder in an oven..... warm and dry

[Gordon]

make sure you keep your powder in an oven..... warm and dry

Very good tip for any powder

Damp and clumpy powder may well lead to problems with powder feeding, coating quality and inconsistency in hardness. Though, I would have thought ~ 30% humidity is pretty dry conditions, well compared to the August/September weather we are having in the UK this year

[chromalloymachi112]

It may be old news by now I am in phoenix az and have similar problems with hardness except it has to do with 307ns and ambient temperature changes. Weird readings especially with the hardness! Untill I started hardness testing after 1 hour of dwell time. Then the readings were constant right where metco says it would be.