There was a very good article on the subject of scratch testing of coatings, etc. in the April 2006 issue of ASM's Advanced Materials & Processes magazine. The authors are employees of CSM Instruments, which has quite a bit of technical information on their website. The new ASTM standard is ASTM C 1624 covers scratch testing. Hardness testing is covered by other standards. There is a good description of the various methods on the CSM site.
