ORIGINAL ARTICLE Tribocorrosion properties of Ti6Al4V after sinking ED machining with glycerin water solution and hydrocarbon dielectric fluids Carlos Augusto Henning Laurindo 1 & Bruna Michelle de Freitas 1 & Letícia Christina Muniz Bemben 1 & Paulo César Soares Jr 1 & Ricardo Diego Torres 1 & Fred Lacerda Amorim 1 Received: 1 April 2019 /Accepted: 13 June 2019 # Springer-Verlag London Ltd., part of Springer Nature 2019 Abstract Titanium alloys are usually selected for orthopedic implants because they are biomaterials that withstand biological environment with combined dynamical mechanical loads and very aggressive body fluids. However, these alloys are considered difficult to be processed by conventional machining, owing to their mechanical characteristics. Due to the ED-machining thermoelectric material removal nature, which is independent of material mechanical properties, it appears as an alternative to conventional machining processes and a technique suitable to modify surface mechanical properties. This work evaluates the ED-machining surface modification influences on the tribocorrosion properties of Ti6Al4V alloy using two different dielectric fluids, a hydro- carbon and deionized water (DI) mixed with a glycerin solution. The analysis shows that the ED machined with hydrocarbon dielectric produces a modified titanium surface with lower roughness and higher hardness due to the formation of TiC phase. The produced surface improves the tribocorrosion and wear properties of the Ti6Al4V samples. The hydrocarbon-machined samples present also a lower friction coefficient when compared with ED-machined glycerin water solution and control samples (Ti6Al4V). Keywords ED machining . Ti6Al4Valloy . Tribocorrosion . Wear . Surface modification 1 Introduction Most of the load-bearing implants like knee, hip, and spine prosthesis demand biomaterials that withstand biological en- vironment with combined dynamical mechanical loads and very aggressive body fluids [1]. Metallic biomaterials such as CoCrMo alloys, 316L stainless steel, and titanium alloys are usually selected for orthopedic implants. CoCrMo alloys and stainless steels present excellent mechanical and corrosion properties; however, the ion and particles release, especially Cr and Co ions, are associated with severe inflammatory re- actions, which can lead to implant loosening [2]. In load-bearing metallic prosthesis, there is a synergism between mechanic wear and corrosion, called tribocorrosion, which is the main degradation mechanism in orthopedic implants. Metallic biomaterials’ corrosion resistance is based on the spontaneous formation of a passive film on its surface, which protects the bulk material from electrochemical disso- lution. This thin protective film (few nanometers thick) could be continuously worn out under the effect of sliding or fretting wear, leading to the exposition of the base metal to the body fluids, accelerating the wear, and increasing the metal-ion levels to the adjacent tissues [3, 4]. CoCrMo alloys, 316L stainless steel, and titanium alloys are materials difficult to be machined by conventional pro- cesses (e.g., turning, milling, drilling) due to special mechan- ical characteristics, which affect the practical performance, quality, and cost of the manufactured products. As reported by Amorim et al. [5], titanium alloys due their mechanical properties are considered as materials difficult to be machined by conventional machining processes. Common failure modes occurring at the cutting tool when machining titanium alloys are the following: notching at the tool nose, flank and crater wear, and chipping and catastrophic cutting tool failure. Deshpande [6] reported that there are very limited works re- garding the machinability of CoCrMo alloys, and technolog- ical information for the adequate machining parameter * Fred Lacerda Amorim fred.amorim@pucpr.br 1 Mechanical Engineering Graduate Program – PPGEM, Pontifícia Universidade Católica do Paraná – PUCPR, R. Imaculada Conceição, 1155, Prado Velho, Curitiba, PR 80215901, Brazil The International Journal of Advanced Manufacturing Technology https://doi.org/10.1007/s00170-019-04011-7