This can be a vague term, but usually hardcoat refers to a very thick and hard anodic coating.
This kind of anodizing is accomplished with a bath similar to the standard sulfuric process, but with the temperature reduced to about 0 degrees Celsius to slow the dissolution rate.
A higher voltage is applied to enable the coating to continue to build after the insulation value of the coating starts slowing down the coating formation.
Hardcoats are generally used in military applications or areas of very high abrasion.
SAF does not currently offer a hardcoat anodized finish, but we encourage you to call for a referral.