So just how tough is DLC? The best way to put it is that the watch industry is a second or third tier user of DLC coatings. The vast majority of research and application of DLCs goes into highly engineered components that depend on DLC’s hardness, friction reduction, corrosion resistance, and tribology advantages. (That’s the study of how one material interacts with another during contact and sliding.) You’ll find DLC coatings on shock absorbers and engine pistons in F1 cars, across the leading edges of fan blades in jet engines, coating critical medical implants, and the cutting tools inside the CNC mills and lathes that made the Apple Watch itself. (DLC extends cutter tool life, improves cut quality and allows for dramatic feed/speed increases.)
I was trying to find a break down of Apple Watch Materials and unfortunately, there’s not a ton of information out there from Apple directly. iMore did have a great break down of various materials and it seems Space Black Stainless Steel is the watch to get if you want the hardest and most scratch resistant use of materials.