I run a machine shop where we run 80% high strength Inconel and other high nickel exotics. These type of materials practically REFUSE to be cut fast. You can do SOME high speed machining with ceramics, but its hard on the part(warping) and the machine and you are limited to mainly large areas that do not have small detail.
I use to work in a shop where we built plastic injection molds. We were milling a pocket in some P20(which is similar to 4130) that was approx. 2" deep and 14" x 14" square. The plate was only 2.5" x 16" x 16", so a majority of the material was being machined away.
With the conventional method using HS cobalt roughing endmills we would get .050"-.060" warpage in the plate and would have to mill the top and bottom of it flat and re-grind the surfaces. This was also rough on the machine as it was a small 30 taper machine. It also took a long time. Its been years, so I dont remember how long it took.
I called the local Iscar pimp and told him what we were doing. The next day he shows up with a 1" diameter 4 flute Iscar HELI 2000, with I think, a 3" or 4" length to it. IC950 I believe was the grade of insert. He tells me to run it 4000rpm, 110 IPM, .030" deep at full diameter, and no coolant, just air blast. I knew the guy was crazy(known him for a long time), but I also knew he was good. I had my doubts. The length of the tool, the rpm, the feed rate, no coolant. It was all too weird, but he was paying for the tool if it fried.
This thing threw a glowing orange rooster tail of shavings and went to removing metal at a rate I had never seen before in steel. The machine was actually handling it quite well also. We would stop every 1/2" of depth and change inserts. The tool was barely warm and the part had NO heat in it. When we were done, it took about 2/3 the time and the plate was only warped .002"-.003". It was the coolest thing since I discovered my dads micrometers were precision measuring tools, not some weak-ass c-clamps. lol
Call your tool rep and see what they have for your situation. For nickel base alloys, I like a 1" 5 flute high helix carbide endmill with a .030" corner radius for removing large amounts of material where a face mill cannot be used. We will go .300" deep at full diameter with these in heat treated 718 Inconel! Your machine has to be stout though.
At times when the latest and greatest new carbide/coating grade will not do what its price tag says it should, I will buy the grade that says its for cutting cast iron. It works well on Inconel believe it or not.
