Stainless steel gear help (galling conserns)
Stainless steel gear help (galling conserns)
(OP)
Any advise on preventing galling on stainless steel gears running dry (no lube). Spur gears are running about 120 rpm and dp24. I was thinking of using gall-tough, but it is not so easy to source. So I am thinking of DLC (diamond like coating), or some other coating.
Thanks for any advice.
Steve Krause
Thanks for any advice.
Steve Krause





RE: Stainless steel gear help (galling conserns)
RE: Stainless steel gear help (galling conserns)
I read a thread about molykote 106 from Dow and I am looking into this also.
RE: Stainless steel gear help (galling conserns)
Mike Halloran
Pembroke Pines, FL, USA
RE: Stainless steel gear help (galling conserns)
I just sent a sent a set of gears out for TiN coating using vapor deposition. The thickness is about 1.6 micron, so I shouldn't have dimensional issues.
I will let you know the results.
RE: Stainless steel gear help (galling conserns)
Does it have to be austenitic stainless? Heat treating is out? You'll have to watch this TIN. Not all Coaters do a good job and it tends to flake off.
RE: Stainless steel gear help (galling conserns)
RE: Stainless steel gear help (galling conserns)
You say this is a medical device application. Is contamination an issue? If so, then any DFL or hard coating will present a problem because they ALL will eventually flake off and create debris.
You also said that you experienced galling in a similar application with Custom 455 at an H900 condition (Rc 48/230 ksi UTS), so it is unlikely that you would fare any better with a "coated" part. Any coating you apply would be very thin and will only be capable of supporting loads within the limits of the underlying gear material itself.
Your best bet would be to enclose the gears and seal/lubricate them with autoclave compatible materials.
RE: Stainless steel gear help (galling conserns)
Currently the device works well with a moly lubricant, but this is a prototype. I need to get the gears to run smoothly with no lubricant. We don't want to seal the unit.
My understanding is the TiN coating is HRc 70. I need it for wear resistance and lubricity purposes, not for load capacity. The 455 H900 application was not a gear, it was a shaft in a bore. The loads I calculate create minimal deflections in the gear teeth, so maybe I can "get away" with the coating.
The device with be used approximately 100 rotations per surgery, so I don't think it will wear away that quickly. It will also be disassembled after every surgery and flushed with hot soapy water, then reassembled and autoclaved.
RE: Stainless steel gear help (galling conserns)
parameters too. Can't you use mineral oil?
Would be better than nothing and non toxic.
RE: Stainless steel gear help (galling conserns)
http://www
There is a fairly new process for specifically surface hardening Austenitic SS from Germany that was to be offered in the US by Swagelock. My information came from Industrial Heating Magazine.
I would also look at Nitronic 60 for both gears, self mated, or as a mate for something like 17/4 PH that has been liquid nitrided. Another material is Gall-Tough that has similar properties as Nitronic 60.
Nitronic 60 Check the full brochure
http://www.hpalloy.com/DataSheets/ni60.htm
Gall-Tough
http://
RE: Stainless steel gear help (galling conserns)
RE: Stainless steel gear help (galling conserns)
One of our medical customers does use a sodium stearate solution that can be applied wet and then dried on. It works well as a lubricant for single piece use, but likely won't work well if the gear is to be used for multiple patients w/ intermittent washing & baking.
RE: Stainless steel gear help (galling conserns)
How is your surface finish?
RE: Stainless steel gear help (galling conserns)
There are some many coatings out there it boggles my mind.
I am getting protos of custom 465 H900 gears and sending them out for TiN coating. The surface finish is Ra=.8 or 32 microinch.
I really wanted to get a DLC coating, but I could not find a vendor to do a proto quick turn around.
Steve
RE: Stainless steel gear help (galling conserns)
RE: Stainless steel gear help (galling conserns)
RE: Stainless steel gear help (galling conserns)
We used PM output gears on high production runs for fractional gearmotor drives. In one demanding application showing premature failures under test, we opted for oil quench after sintering by recommendation of mfr. Not only did it serve as a quenching medium, it provided internal lube. PM being porous to some extent provides space for lube in the matrix. Highly recommended.
RE: Stainless steel gear help (galling conserns)
Just interesting to see how the competition is doing things. Thanks for the update!