You have to be careful when you get into the world of coatings. Different coatings give you different advantages on different materials. The main advantage of the TiAlN coating is wear resistance. The coating is considerably harder than the carbide that it will cover so the edges of the tool will last longer. This particular coating needs to reach a certain "activation" temperature before it will work, however(I think it's around 700-800 degrees). The way it was explained to me is that when activiated, the coating provides the wear resisitance of a ceramic cutter with the strength of a carbide substrate. One of the ways to activate it (or reach the temp) is to increase the rpm. Since Feedrate = RPM x Feed per tooth x # of flutes, the higher the rpm, the higher your feedrate.
That's some of the theory behind the coating.
However also keep in mind that no matter what coating you have on an endmill,you can only push a 1/4" endmill through 316 S.S. so fast before....BINK!!! you lose it.
To make a long story short, the wear resistance of the coating is well worth the price in difficult materials. As far as feedrate gains, that's up to the machinist. Remember no guts no blue chips!  |