DMLS inconel718 part questions

[aroundhere]

Im thinking of having a part made since the EDM shop is backed up. Is there any reason that I couldnt use this part on a downhole tool with temps of 350F at 15k psi? Its not a pressure vessel. I know the temp should be fine. I am concerned about the corrosion if there are microscopic voids in the part. Ive never used a 3d metal sintered part, so I don't know much about them. The price on this part is not that bad and I can have it quickly. If anyone has tried this, please let me know.

 

[KENAT]

aroundhere, the material properties of a sintered piece may not be the same as a cast/forged/machined piece - have you allowed for this in any calculations of loading etc.?

Posting guidelines faq731-376

http://eng-tips.com/market.cfm?

(probably not aimed specifically at you)
What is Engineering anyway: faq1088-1484​

 

[aroundhere]

KENAT,
The material spec had an AS BUILT that looked ok except the elastic modulus was blank but still had a yield strength of 95ksi unless I am reading it wrong. Then has a AMS5662 and 5664 solution anneal and age hardening that has specs that are similar to bar stock. I have to find out if they do this or not. The part is a retainer and doesnt see any loading, but would still like to know. I am finding that some of these DMLS services do not have an engineer on staff that can help. This is all good info and I do need to determine what I would get.

see spec sheet attached and I added the link to the spec sheet site

thanks

Link

 

[tbuelna]

aroundhere-

The Inconel 718 powder will be laser sintered in an inert atmosphere, but as Kenat noted the microstructure of the DLMS part will not be as good as forged (AMS 5662) or wrought (AMS 5664) bar. At best you might get something similar to an investment cast material (AMS 5383). The mechanical properties shown in the data sheet you linked seem overly optimistic since they are at the upper end of what MMPDS-01 lists for forged and wrought bar. For your reference I've attached the relevant pages from MMPDS-01 showing min mechanical properties for AMS 5383, AMS 5662 and AMS 5664.

As to whether a laser sintered material would be a suitable replacement for forged/wrought material in your particular application, first you should review the requirements contained in your engineering documentation and/or your customer's PO. It is never a good idea to make a material substitution for a demanding application like this without getting approval from everyone involved.

Your concerns about defects in the laser sintered material are valid. For example, since the material is built-up in discrete horizontal layers the surface a DLMS part has numerous tiny steps where the laser is started/stopped. These abrupt fusion boundaries might pose a stress problem, but they can be eliminated by making the part over-sized and removing the outer surface layers. The material data sheet you linked seems to acknowledge this problem, since it had a footnote stating that the properties listed only applied in one direction relative to build-up.

If internal material defects like voids or incomplete fusion are a concern, you can employ the same NDI techniques used with fusion welds to check for them. Or you could even have the parts HIP'd to consolidate these internal defects.

Having said all this, the reality for your particular case is that it is probably much more cost effective and expedient to simply make the parts the same way you have been (wire EDM from wrought bar) except using an outside vendor.

Best of luck to you.
Terry

 

[aroundhere]

thanks tb...I am going to get in touch with someone at one of these DMLS services and see if I can get more info. I considered this for one prototype part due to lead time, and we can still test while waiting on the edm shop. To be honest, I didnt even know that inconel and 17-4 could be built like this. I do remember the titanium 3d printer that was around years ago when we bought our plastic printer.