Ball cratering an efficient tool for 3 body microabrasion of coated systems

Ball cratering is a well established technique for assessment of coating thickness. The proposal of a pre-standard (ENV-1071-2) has been submitted to the European standardisation organization CEN. The present work is part of a completed standard measurement and testing programme "crater" addressing the subject of using this type of instrument for the determination of the intrinsic wear rates of thin coatings (for which the draft of a CEN standard prENV 12071-6 is being set up presently). The global composite wear after coating perforation is generally assumed to be a linear convolution of the substrate and the coating wear rates. It is shown that the applicability of such an approach depends on the local damage mechanisms in the coating and at the coating/substrate interface. In the case of high hardness DLC on steel or titanium alloy substrates, load carrying continues to be dominated by close to two body scoring abrasion insured by the highly wear resistant DLC annulus, while in the perforated centre rolling contact between the abrasive slurry and the substrate material prevails.