Tungsten carbide inserts are naturally gray in color, but you’ll often see them in a variety of other hues. This isn’t for decoration — the colors come from the coating material applied to the insert. If an insert has more than one coating, the visible color will be that of the outermost layer.
The coating on an insert is there to improve performance. Plain carbide by itself is tough, but coating it with harder materials like titanium nitride or titanium carbonitride increases wear resistance and tool life.
Interestingly, tungsten carbide’s hardness isn’t just useful in cutting tools — it’s also why tungsten carbide jewellery stays lustrous and scratch-proof over time. Unlike softer metals like silver or gold, a tungsten carbide ring won’t easily mar, and because it’s hypoallergenic it’s less likely to cause reactions for people sensitive to metals.
On the Moh’s scale of hardness, tungsten carbide scores about 8.5 out of 10, with diamond at the top of the scale. That’s why carbide inserts hold up so well under heavy cutting loads and harsh machining conditions.
