What is the deal with Inconel

Over the past year or so I have been machining a lot of super alloys. Initially I thought "oh god this is gonna SUCK"

But after awhile it really is just like....okay this is another material to cut. Maybe it is because I have had to cut such a wide spectrum of materials over my career but I would honestly rather machine inconel over any ceramic material i have touched. I have done both 3D printed and bars.

As an example I am turning a 2" 718 shaft with about 60%+ material removal. I surely expected it would be eating my "general purpose" Kennametal inserts cut after cut. Well not so...1 4 sided insert lasted the entire roughing op on the first side. .06DOC...100SFM..0.004-0.005IPR and boom, she is squeeling and yelling but it is basically doing just fine.

Monel same deal. You just get the proper tools and the proper speeds and feeds and you are going to be fine. It isn't rocket math.

I have yet to touch Stellite or some of the cobalt alloys so I don't want to say those are easy by any means.

If you're going to be cutting 718HT and some of the tougher alloys...perhaps ceramics are going to be better. Just need the right tool for the job and the proper cutting data.

Am I crazy for actually liking cutting super alloys?

Carbide tooling has come a long way in the last thirty years, I'm sure the older posters here would agree. But the reputation of the tougher alloys stays the same, maybe that should change.

Everything is its own nightmare. There is that one guy on Youtube who cuts nothing but super alloys in an integrex and he does it all like its no biggie, because it is for him.

Not at all, I am in the chemical industry and primarily cut all of the above. Once you have the recipe figured out it's just another predictable process. The only materials I still fear are the especially gummy and heat resistant ones like hasteloy B, it seems you can either cut slow enough to make the tool last and deal with the stringy chips or cut fast enough to get chips and burn up the tools, never both. I also dislike zirconium because of the flammability. Stellite is just terribly abrasive, I find heavy cuts at slow feeds and slow sfm is the ticket. The most unmachinable material I deal with has got to be Haynes 25 though, unattainable, nigh un-cutable, atrociously expensive, and will practically will itself into the scrap bin, harder than a whores heart and filled with twice as much hate.

Kingbob said:

Not at all, I am in the chemical industry and primarily cut all of the above. Once you have the recipe figured out it's just another predictable process. The only materials I still fear are the especially gummy and heat resistant ones like hasteloy B, it seems you can either cut slow enough to make the tool last and deal with the stringy chips or cut fast enough to get chips and burn up the tools, never both. I also dislike zirconium because of the flammability. Stellite is just terribly abrasive, I find heavy cuts at slow feeds and slow sfm is the ticket. The most unmachinable material I deal with has got to be Haynes 25 though, unattainable, nigh un-cutable, atrociously expensive, and will practically will itself into the scrap bin, harder than a whores heart and filled with twice as much hate.

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Here's to hoping I never encounter Haynes 25! haha.

I actually think machining SOFT materials is harder...a non extreme example is this part that is the 2" bar. I made an aluminum test article to dial in the process and hit everything in spec (+0 -0.0006 on most of the 15 diameters...) and getting it dimensionally stable was a massive PITA. Nailed it first try on the Inco.

More extreme is UHMWPE...god that is awful. I can't believe people actually design parts from that material. PTFE is super soft but also quite dimensionally stable. Can be a pain but nothing is worse than UHMWPE.

Milland said:

Carbide tooling has come a long way in the last thirty years, I'm sure the older posters here would agree. But the reputation of the tougher alloys stays the same, maybe that should change.

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This probably has a lot to do with it, for sure. People always say carbide/tooling improvements have been incremental, but 30 years of incremental improvement leads to a massive gain in performance by the end of that time period.

kustomizingkid said:

Everything is its own nightmare. There is that one guy on Youtube who cuts nothing but super alloys in an integrex and he does it all like its no biggie, because it is for him.

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Edge Precision. He does a ton of oil and gas work. Here is his latest project...looks "simple" until you see the section view! Oh an it is some exotic Titanium alloy.

Titanium Part Plan Tools and Setup - YouTube

Agreed 100%, hard metals just seem more predictable.

They used to say Titanium alloy was hard to machine. Now it's just another material.

Looks like I might be cutting some Platinum Iridium alloy in the near future; doing my research.

I agree, once you learn to deal with it, it's not that bad. Just slow down and watch the tools more often.

We mostly cut 316SS. Another facility was overloaded and needed some assistance with Super Duplex 2507 (I know, not as difficult as 718, but difficult all by itself) so it was moved to my location. I was very familiar with it, but the operators were not. I had developed most of the Inconel, Hastalloy, and duplex processes about 10 years earlier at the original facility.

I tell you, it was like dealing with the 5 stages of grief...
Denial - There's no way this can be normal (tool life, chips, scrap parts etc...)
Anger - The Mfg. Engineer (that's me) doesn't know what he's doing...doesn't know how to make a process
Bargaining - Can't we test some new tools...can't you make them last longer
Depression - This sucks
Acceptance - This really isn't that bad....just need to watch my tools more often (this was almost a word-for-word quote two weeks later from the operator)

You would be signing a different tune if you were back in the day before insert tooling became common place.
I think the crap was called 52 nickel or the like. I was running it on a D series Citizen lathe, not sure if you would call it an NC or CNC. I had good old brazed carbide tools. Even though the parts were small and simple a set of tools lasted about a half dozen parts.