Q: How do I tell if my hard drive has suffered mechanical failure to the platter surface?
A: Platter damage is typically caused by a head fault or contamination within the drive’s chassis.
In most cases the heads, or a foreign object, make contact with the platter and damage it. Most commonly this damage is localised to a specific area of the platter, in some more rare cases, this damage can destroy the platter surface entirely and leave only dust within the drive.
In these circumstances, the only way to assess the level of damage to the platter, is to take the hard drive apart, and visually inspect it under an appropriate microscope.
This should only really ever be done in a certified clean room as the danger is that you may introduce dust particles into the hard drive and compound the problem.