Why Carbide Drills Are Often Coated

A carbide is a ceramic-adjacent compound formed of carbon and another element that is less electronegative, typically but not always a metal.

Carbides are extremely hard and stiff materials, which gives them good wear resistance. Despite this, carbide drills are more brittle than some alternatives like high-speed steel, or HSS.

So, while it is true that metal cutting tools like carbide drills will stay sharper longer than steel metal cutting tools, and that they can generally be run at higher speeds and temperatures, they are far more brittle and are likely to shatter or snap if misused. 

That being the case, carbide drills are often treated with special coatings such as AlTiN, TiCN, or DLC, which confer special attributes to the cutting tool. This post will dive into some of the reasons that specially-coated carbide drills deliver value. 

Carbide Drill Coatings: What’s the Point?

While different carbide drill coatings provide different benefits, there are numerous reasons that they are coated. For instance:

• Certain carbide drill coatings, like nitrides, increase the surface hardness of the tool. While carbide is hard to begin with, a nitride or diamond-like carbon treated carbide drill will be even harder. This improves cutting efficiency and potentially extends tool life. 
• A higher surface hardness rating, conferred by more than one type of carbide drill coating, can enable more efficient cutting and machining as compared to a comparable tool without such a coating. 
• Some surface coatings, like TiCN (titanium carbon nitride) or ZrCN (Zirconium Carbon Nitride) improve the permanent dry lubricity of the cutting tool. This means even at higher operating speeds, less friction will be produced, which will incur less thermal stress on the tool. 
• Some coatings, as a result of their higher lubricity, facilitate chip evacuation. Expedient chip evacuation not only reduces stress on the tool and improves cutting efficiency, but can improve the surface finish of the workpiece as well. 
• Certain surface finishes also reduce adhesion. When run at higher speeds and temperatures, some materials can have a habit of welding or sticking to the flutes of the carbide drill. Certain coatings discourage this phenomenon. 
• Some carbide drills get softer and less efficient when they overheat. This is referred to as “thermal softening”. By reducing friction and thereby thermal stress, some carbide drill coatings and finishes can help discourage this phenomenon. 

These are just some high-level examples of some of the types of benefits conferred by carbide tool coatings, but they do a good job of offering some insight into the value added. 

Where to Stock Up on Carbide Drills, End Mills and Other Metal Cutting Tools 

Want to learn more about specific carbide drill coatings and finishes, or just need a supplier that can help keep you equipped with carbide drills, end mills, and other metal cutting tools and machine tool accessories? Visit TMT Toolbox to learn more about what they sell.

For More Information About Lathe Chucks and Carbide End Mills Please Visit: TMT Toolbox.