What exactly were you trying to determine with your extremely un-scientific test? I don't generally, (or ever), drill liquids. The oxide coated bit will wear out just about as fast as an uncoated high speed steel bit, except in wood that has high acidity resins, like oak and some hickory. The carbide bit is a good all purpose bit for wood and most metal. Masonry bits have carbide tips also. The cobalt bit is for cast iron and hardened steel. The titanium coated bits are usually poor quality steel and break very easily.

Now i know what i need for drilling that hno3/hf container

Much easier to pull electrons from gold oxide. Gold metallic bonds are much stronger so thermodynamicly less favourable to break

Cobalt are for stainless steel and work fine. The rest dunno.

So what?

try in milk. you could be surprised.

Black oxide was a huge surprise. I love this channel! It's sort of a do it yourself / extreme reagents channel. I would recommend this channel to anyone who likes @ExplosionsAndFire, the Australian shed chemistry channel.

who is going to do this to a drill bit? lol