Influence of Thickness and Ti Interlayer on Scratch and Wear Resistance of CoCrNi Medium Entropy Alloy Coatings

CoCrNi-based medium entropy alloys (MEAs), as one of the derivatives of the Cantor (FeNiCoCrMn) high entropy alloy, have attracted extensive research interest due to their remarkable mechanical properties and outstanding radiation and corrosion resistance. In this work, scratch and wear testing was carried out on various MEA CoCrNi coatings (of different thicknesses, both with, or without, the presence of a Ti interlayer) to study the effects of both coating thickness and the inclusion of the Ti interlayer on scratch adhesion strength and wear performance. For the MEA coatings directly deposited onto the substrates, the coating adhesion strength weakened with an increase in coating thickness. Counterintuitively, the introduction of a Ti interlayer was found to be detrimental for the scratch adhesion strength compared with the samples prepared without an interlayer, where severe surface fracture was observed for the thicker MEA CoCrNi coatings. Additionally, the wear results show that thinner CoCrNi or CoCrNi/Ti coatings demonstrate better wear resistance than their thicker counterparts. It is believed that the residual compressive stresses present in these coatings contribute a significant role in influencing their wear performance. © ASM International 2024.