Is graphite lubricant safe for metal parts?
While I am not a chemist, this goes against anything I understand about carbon and its common chemical forms. In the crystalline diamond form, carbon is extremely hard and quite useful as an abrasive. However, in the form of graphite, carbon lies in sheets that are very loosely bonded to each other. These sheets can easily slide against each other under shear stresses because of the very weak bonds, so graphite forms an excellent lubricant.

I would suggest your source is incorrect.