Stellite 6

[RobinHood]

I most likely have a project coming up where I’ll be working with Stellite 6 (6B in particular). First time for me.

Already spoke with Kennametal / Stellite in Belleville, ON, to source the metal/get info. Carbide or Ceramic tooling should work I am told. “Going to go through lots of inserts/edges“. Speeds and feeds are much different from regular SS they said. There will probably be some grinding as well and for sure lapping to get the parts to mate.

One-off part(s) for now. May need more in the future as the part(s) wear out again.

No CNC, all manual machines in the shop.

Anyone ever worked with this stuff? Any hints and tips would be appreciated. Thanks.

Cheers, Rudy

 

[Brent H]

Hey Rudy,

The valve seats on our main engines are Stellite. It is very very hard. Only ever ground or lapped it in. Takes the pounding and heat with valves closing at 175 HP and 420 degree exhaust. Probably need to have the coolant flowing great guns to keep any tool life?

 

[RobinHood]

Thanks Brent for your input.

The project is a valve/valve seat for a homogenizer used in the food industry. It looks something like this.



According to documents from Kennametal, Stellite 6B has a hardness of 33-42RC. Hence they say that I should be able to turn it at slow speed/ feed (slow for Carbide that is). We’ll see.

 

[Brent H]

That looks quite detailed for a valve - several seats and valve faces. must have some pressure behind it - hopefully you can get it really close and only have a bit of lapping.....

 

[RobinHood]

Yes, 2500+ PSI I heard. But it corrodes fast due to the acids in the liquids passing through. Ends up looking like this:


They are now redesigning the valve and seat to try and make it last longer. This is where I come in to make the newly designed, one-off parts - if the project goes ahead.

 

[PeterT]

No experience with that material, sorry. I bought an Ali CBN insert a while back as an order add-on after watching either or Stefan/Renzetti video. I would think the Kennametal folks know their stuff but the project I had in mind has been shelved, so if you want to give it a go let me know. What the 'real' specs are is anyone's guess.
https://www.aliexpress.com/item/32898158898.html?spm=a2g0s.9042311.0.0.27424c4duHQOfZ

 

[trlvn]

I take it this a similar alloy to the Stellite lathe tool bits?

http://www.conradhoffman.com/stellite.htm

I have a couple of pieces of Deloro Stellite and Tantung "G" that I got in an auction box lot. The page I linked to recommends not quenching the bit while grinding. I found that bit of wisdom after I'd done just that. Sure enough, the ground end snapped off when I was taking a moderate cut...and this on my tiny Atlas 6" lathe. The Stellite was noticeably harder to grind than regular HSS. I've been thinking to make a threading tool with this material since it ought to have superior wear resistance compared to HSS. Haven't got around to it, though.

Does the "6B" alloy have similar thermal shock restrictions? Would it hit those high-low temperatures in your application?

Craig

 

[johnnielsen]

My experience with stellite is only as a cutting edge for machining steel and it is fantastic for that but a file skipped across rather than marked the stellite so harder than Stellite 6B. Solid machines and ceramic tooling are an absolute requirement.

 

[RobinHood]

Thanks for all your replies, appreciate your comments/info. Thanks for the offer Peter, I’ll let you know.

Yes, there are cutting tools made of Stellite - I found out that they are a different composition and way, way harder than the Stellite 6B that the client is considering for the valve. Just found out that they are now also considering using Tungsten Carbide (Silver Soldered onto a base of SS) as the valve / valve seat - getting more and more interesting / exotic by the minute...

Here is a link to Kennametal’s Stellite info.

https://www.stellite.com/us/en/products/stellite-6b.html

 

[Rusty Metalhead]

For high corrosion applications our choice of metals at the university was Hastelloy.
Also a tough to machine metal. Toughest job I remember was drilling a .017 hole on the lathe.....
-G

"HASTELLOY alloy shows unsurpassed resistance to corrosion in seawater atmosphere. Exposed at Kure Beach, N. C., since 1942,
HASTELLOY C sample continues to keep its original surface finish while the rest of the test allots have disintegrated long ago."

http://www.haynesintl.com/tech-brie...formance-alloys-for-seawater-service-(H-2102)

 

[PeterT]

Likely the answer is no, but any chance the part can be made from high grade tool steel - ie. machined in annealed state, then hardened?
https://www.moldmakingtechnology.co...hree tool steel,, form presses, and extruders.

 

[RobinHood]

The valve and seat are coming in contact with food. There are quite tight regulations as to what metals may be used - so I am told. Pretty much all SSs are a go. Obviously Stellite is approved as this is the original material. So not sure about “traditional” tool steel (like 4140 and the like). I like the idea of hardening after machining...

Some SSs can be hardened after the fact. I have no way of doing that properly though.

I did read about Hastalloy: quite the material. More impressive since it (and Stellite for that matter) were first discovered (“brewed“ may be a better term maybe?) over a 100 years ago!

 

[Brent H]

Our old bow thruster was designed with a Ferralium Stainless steel shaft as it was a design based on a pulp and paper mill. The alloy of stainless was very good at resisting corrosive damage form Chlorine used to bleach the pulp and also very good for wear caused by sand and pulp. Not sure how it would work as a valve? It was hard and took some time for the lads to machine. We use it as bolts to hold our rudder posts to the rudder and also for the bolts the hold the rudder Gudgeon on for the pintle bearing: https://www.hpalloy.com/Alloys/desc...uplex,fatigue strength in marine applications.

Don't ask me why I have this in my cabin but here is the bolt:

 

[YYCHM]

Our old bow thruster was designed with a Ferralium Stainless steel shaft as it was a design based on a pulp and paper mill. The alloy of stainless was very good at resisting corrosive damage form Chlorine used to bleach the pulp and also very good for wear caused by sand and pulp. Not sure how it would work as a valve? It was hard and took some time for the lads to machine. We use it as bolts to hold our rudder posts to the rudder and also for the bolts the hold the rudder Gudgeon on for the pintle bearing: https://www.hpalloy.com/Alloys/descriptions/FERRALIUM255.aspx#:~:text=FERRALIUM 255 is a duplex,fatigue strength in marine applications.

Don't ask me why I have this in my cabin but here is the bolt:

View attachment 10845

That was made in your ship's shop?

 

[Brent H]

@YYCHobbyMachinist , it was made at the machine shop in old Port Weller ship yard circa 2002. They machined one of our original bolts by error and this was a spare in case the "oops" did not pass inspection.

There are four of these holding on the lower rudder gudgeon (bushing retainer).


@RobinHood : sorry I goofed with the Ferralium - although that might help with your project - the bolts are made from Aquamet 22 : https://www.aquamet.com/aquamet-22 another very tough stainless steel.

 

[Brent H]

I do not want to hack @RobinHood's thread - here are a couple pics of the installation so you know what I am discussing : the Kort nozzle also has a welded stainless wear ring going around the inside and this was done to prevent cavitation wear caused by the low pressure to high pressure zone at the propeller tips.




The Ferralium shaft was fitted at the bow thruster. It may be a material to experiment with??

Does the valve open and close frequently to dump after the product is blended?

 

[Johnwa]

@RobinHood that looks like a good application of EDM or ECM.
https://www.voxelinnovations.com/post/ecm-vs-edm

 

[Chicken lights]

Our old bow thruster was designed with a Ferralium Stainless steel shaft as it was a design based on a pulp and paper mill. The alloy of stainless was very good at resisting corrosive damage form Chlorine used to bleach the pulp and also very good for wear caused by sand and pulp. Not sure how it would work as a valve? It was hard and took some time for the lads to machine. We use it as bolts to hold our rudder posts to the rudder and also for the bolts the hold the rudder Gudgeon on for the pintle bearing: https://www.hpalloy.com/Alloys/descriptions/FERRALIUM255.aspx#:~:text=FERRALIUM 255 is a duplex,fatigue strength in marine applications.

Don't ask me why I have this in my cabin but here is the bolt:

View attachment 10845

Now that’s a bolt

 

[RobinHood]

Does the valve open and close frequently to dump after the product is blended?

Brent, if I understand the homogenization process properly, that valve does not move. The GAP between the valve and valve seat is set (and adjustable) to get the result. The raw product (milk) enters through the valve seat orifice at high volume and pressure (up to 20000 l/h and 2500 psi, depending on the design of the valve & the size of the homogenizer). As the product is forced through the tiny gap, the velocity increases even more and the pressure drops. This causes both turbulence and cavitation. Both of these phenomenon cause the little fat globules to be reduced in size and made uniformly small. This is called homogenization (of the fat molecules).

Here is a link to the U of Guelph‘s description of the process:
https://www.uoguelph.ca/foodscience/book/export/html/1908

My brother used to work @ the U of G in the food science department. He now works for a private company that maintains and (re)designs food processing equipment.

This is what this project is all about: improve on an old design to see if they can make it better. So basically a one-off design change, proof of concept and then (possibly) small series production.

Yes, EDM /ECM is certainly a possibility. Not sure on the cost associated with that and who would want to just make one part to see if it works?

 

[Brent H]

Ah, ok Rudy, now that is making sense with the various annular rings to re-direct flow. Should be very interesting to see the final design! Would titanium coating assist with wear resistance? I believe the milk coolers are titanium plates? - same style as our Alpha- Laval sea water coolers.