Real world? No.
Diamond is the hardest known natural substance, and is harder than anything but a couple of exotic materials created in the past 5 years.
However, it has a property called perfect cleavage (insert jokes here) which is due to its crystalline structure. If struck at the proper angle, diamond will cleave into 2 pieces along a perfectly smooth plane (slicker than teflon).
However, in a fantasy world, there's nothing to say that a specially treated diamond couldn't have such properties. Indeed, its very perfection should make it an ideal subject for enchantment. I'd probably use it for an arrow of slaying, if anything.