Ceramic inserts, up to 60 Rc, not happy with interrupted cuts. 2000 FPM so the chip rises red and loops over turning darker before it hit's the lathe, around .010" max DOC and a fine feed, watch your insert nose, but they last quite a while.
Also, regular negative carbide inserts run around 100 FPM, still can't take deep cuts but still works under 50 Rc OK, of course the speed shouldn't make the light grayish blue.
I don't claim to know it all but these things seem to work well for me.
Just the cylindrical part at the top ? Should be a picnic. Tranny gears are normally carburized, use any old carbide, take off .050 or so on a side, and the core should be about 35 Rc. I usually nail it in one pass with negative rake. After that anything works.