Abstract
AISI 420 stainless steel is currently used in the manufacture of surgical and dental instrumentation due to its hardenability, acceptable biocompatibility and resistance to corrosion. However its resistance to wear is relatively low and therefore multiple strategies of surface modification are used to reduce the wear volume and to confer other specific properties on this steel. In this work, TiAlN coatings doped with five different content proportions of Ag and Cu nanoparticles (11 at.% to 20 at.%) were deposited onto 420 steel by means of DC magnetron sputtering, using two targets of Ti/Al and Ag/Cu (both 50/50 at.%), which were placed facing each other at 180° and spaced 42 cm apart. The microstructure, and chemical and phase composition, were analyzed by X-ray diffraction, scanning and transmission electron microscopy and energy dispersive X-ray spectroscopy, while roughness was determined using atomic force microscopy. Hardness and Young's modulus were evaluated by nanoindentation measurements. Finally, the tribological properties were assessed using the ball on disc test method. The composite coatings initially showed a continuous decrease in hardness and a significant reduction in the coefficient of friction and wear volume with the increase in Ag–Cu content, due to the solid lubrication effect of the metallic nanoparticles. However, above 17 at.% of Ag–Cu, the coefficient of friction and wear volume of the coating increased, due to the low hardness of the coating, which lead to the wear process being mainly cohesive type between coating and substrate, and adhesive type between coating and ball. The lowest wear volume, of 7.7 × 10−5 mm3, was exhibited by the coating deposited with 17 at.% Ag–Cu. This was much lower than that of uncoated steel which was 5.4 × 10−4 mm3. This new nanostructured coating could be considered for potential application in manufacturing processes where protection of tools against wear is required, due to its adequate balance between hardness and wear resistance.
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