30+ years in metal cutting... Tungsten ("W") and carbon ("C") are combined in an alloy typically called "carbide" in the manufacturing. The high strength of tungsten, as well as good thermal properties, make it a good choice for cutting tools that can take a beating. Alloying it with carbon gives it a good crystalline lattice structure that allows it to be tougher (less prone to fracturing) than just tungsten, less prone to deformation, and able to be more easily formed into cutting tools through sintering or other production methods. Rotating tools (drills, endmills) that are used for cutting exotic materials, or that can be used for long tool life, are typically made from solid carbide. Less expensive tools can be made with carbide tips that are brazed onto a tool steel body. Such tools can also be made with replaceable carbide cutting tips or edges that can be quickly and easily replaced. Non-rotating tools (such as used on a lathe) typically use a replaceable cutting tip, generally called an "insert." In most cases, the carbide used on cutting tools is coated with a titanium- or aluminum- based coating that serves as a 'shield' of sorts that helps remove the cut material and the heat generated by the cutting forces, allowing the carbide to last longer before wearing down. That's a 'quick' answer; do you need more specific info?