Carbide stays sharper longer. While it might be more brittle than other end mills, we’re talking aluminum here, so carbide is great. The biggest downside to this type of end mill for your CNC is that they can get pricey. Or at least more expensive than high-speed steel. As long as you have your speeds and feeds dialed in, carbide end mills will not only cut through aluminum like butter, they will also last quite a while.
Aluminum is soft when compared to other metals. Which means chips can clog up the flutes of your CNC tooling, especially with deep or plunging cuts. Coatings for end mills can help alleviate the challenges that sticky aluminum can create. Alu Speed Coating-TiB2 base coatings are slippery enough to help keep chips moving, to avoid built-up edges and offering maximum coating adhesion.