It can happen. The carbide coating has a mechanical bond to the screw surface. If the screw surface moves or flexes, the bond can be weakened which may lead to a release of coating. What can cause this movement? Excess heat such as a torch or cleaning oven can expand the screw surface. A cold start can result from operating equipment before sufficient heat input (soak) to soften any remaining polymer in the system. Non-compressible tramp material will gouge the screw surface and remove coating at the contact point.