Localized corrosion of laser marked M340 martensitic stainless steel for biomedical applications

Abstract

Martensitic stainless steels (SS) are used to produce dental drills and other cutting tools. Besides elevated hardness, in biomedical applications corrosion resistance to body fluids and cleaning substances is expected. It has been previously shown [1] that laser marking increases pitting susceptibility of Mo-containing austenitic SS for implants in 0.14M Cl- only if polarized anodically at potentials higher than 0.7V above the open circuit potential. In the case of surgical tools, laser marking is necessary for identification and to indicate the penetration depth of the cutting tool. In the present work, we studied the influence of laser marking on the localized corrosion of martensitic M340 (17.3wt% Cr, 1.1wt% Mo). Fig. 1 shows current maps obtained by the vibrating electrode technique (SVET) at increasing exposure times in 0.1M NaCl superposed to the “8” numeral drawing marked on M340. Laser marking not only increases the susceptibility to pitting, but also creates cathodic sites, probably due to increased conductivity of the oxide