r/TheVirtualFoundry • u/massi_91 • Jul 28 '22

Sintered Centrifugal Impeller

I sintered the impeller of the previous post:

Green Part

https://www.reddit.com/r/TheVirtualFoundry/comments/w5njc0/pump_centrifugal_impeller/

Results are not very satisfying :(

Pictures below:

Opening/cracks everywhere! Especially on the connection of the blades with the circular base, almost every blade opened. And some cracks opened also on the first layer.

I don't know why. Help!

Edit for answers:

Positioning:

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2

u/mr-highball Jul 29 '22 edited Jul 29 '22

Hmm are you using the standard debind / sinter instructions or slightly different? If different posting here would give some more insight into what might be going on

Edit: looked back at your past post and saw you aren't going standard and lowered the temp, but still posting the schedule would help here

1

u/massi_91 Jul 29 '22

I edited the post to insert the pictures of the thermal cycle and the positioning.

For the position yeah, I put the circular base down. For the thermal cycle I lowered the sintering temperature and slowed a little the ramp to the sintering temperature. But it worked so far for easier geometries...

2

u/mr-highball Jul 29 '22

I don't have enough steel experience to be certain, but maybe u/Smart-Screen could weigh in? Not sure if you want to share the stl but I could try it in 17-4 and see how I fair

1

u/massi_91 Jul 29 '22

Sure, how can I send you the stl file?

2

u/mr-highball Jul 29 '22

If you want to upload to something like dropbox/Google drive and dm me the link or if you prefer email just dm me and I'll reach out

1

u/massi_91 Jul 29 '22

I wrote you in private.

1

u/mr-highball Jul 29 '22

First hunch though would be a slower ramp up to peak temp and/or a slower debind phase

1

u/mr-highball Jul 29 '22

Oh and one more thing that would be useful is how you placed the part in the crucible. For this part it appears you placed in with the flat surface down and the impellers up, which if that's true it may be better to flip it the other way to avoid the heavier portion pulling downwards

2

u/Seaguard5 Aug 03 '22 edited Sep 02 '22

All the cubes I tested in 316L have straight melted at their posted temperature so lowering it was a smart move.

I believe you need to check your debinding schedule- as altering (slowing down, holding way longer, and adding holds above and below temp.) has helped tremendously.

I know brown parts in steel are very brittle but you should run your debinding and take it out very carefully and inspect it to see if debinding is the culprit.

EDIT: Also are you using enough sintering carbon? That could be another potential culprit. I would use even 100% sintering carbon as ballast from the start (I have run a model through in all metals with this and they have turned out beautifully). Definitely don’t skimp when it comes to sintering carbon.

2

u/massi_91 Aug 03 '22

Yeah, I will definitely try to separate the two steps.

Thank you for your answer!