I'd go to a coated positive shear insert so you can get under the surface and peal it. I'd bet the insert your using is rubbing and work hardening the surface. Inconel has some peculiar properties that must be dealt with and the main is to keep the insert sharp and positive, especially when taking a light finish pass. some inserts have a land on the edge and you want the sharpest positive in a good grade insert. For roughing it is a little bit different but similar, just keep watch on the insert and when it starts to feel dull get it out quick and start fresh with new corner. The harder you push inconel the harder it is going to push back at you. It is tough and abrasive yet appears gummy at the tool point. you have to keep the chip flowing smooth or it will pile and push.