Vol.:(0123456789) 1 3 Journal of Bio- and Tribo-Corrosion (2018) 4:51 https://doi.org/10.1007/s40735-018-0166-8 Tribo-Corrosion and Corrosion Behaviour of Titanium Alloys with and Without DLC Films Immersed in Synthetic Urine L. O. Paula 1  · A. C. Sene 1  · L. A. Manfroi 1  · A. A. Vieira 1  · M. A. R. Ramos 1  · N. K. Fukumasu 3  · P. A. Radi 1,2  · L. Vieira 1,2 Received: 6 May 2018 / Revised: 22 June 2018 / Accepted: 10 July 2018 © Springer Nature Switzerland AG 2018 Abstract Nowadays, potable water is becoming scarcer, and chemicals components present in wastewater increase corrosion of devices and decrease its lifespan, especially from bearings used in water recovery system. The bearings are subjected to severe corrosion due to harsh environmental conditions from urine composition. 60NiTi alloy which was developed to attend International space station requirements as a resistant material to recycle wastewater to potable water, together DLC flm as a solid lubricant, could be new protective material to avoid tribo-corrosion and corrosion from devices under hostile environ- ment. In this work, we compared the tribocorrosion resistance of 60NiTi, also named as NiTi60T and thermally treated, and Ti–6Al–4V alloys with and without diamond-like carbon (DLC) flm. The NiTi60T is a promising candidate to be used for the centrifuge bearings to expand their lifespan when in contact with synthetic urine. The DLC flm presented high levels of wear resistance, metallic adhesion, and corrosion protection for both tested alloys. 1 Introduction Materials that are suitable for use in sliding contact, such as bearings, are classifed in four broad categories [1]: (1) hard- ening steels; (2) superalloys and austenitic stainless steels; (3) ceramic; and (4) non-ferrous alloys, which include cop- per, zinc, and plastics [2–4]. Materials such as ceramics and silicon nitride possess high corrosion resistance. However, they have low thermal expansion coefcients and are brittle and are thus incom- patible to machine designs. Also, hardened steels such as 440C tool steel and M50 have poor corrosion resistance [5]. In most applications, design surface modifcations can be made to account for the shortcomings of the bearing mate- rials. However, in some instances, it may be benefcial to use material that provides corrosion resistance and hardness and is also both manufacturable and easy to incorporate into mechanical systems. Since 2004, NASA has been exploring any possible solu- tion ofered by NiTi intermetallic for bearing applications [2]. The manufacturable bearings which use NiTi alloys can be traced back to the early work of W. J.Buehler et al., from the Naval Ordinance Laboratory during the late 1950s [2]. The designation NITINOL often used for these alloys is an abbreviation for Nickel-Titanium Naval Ordinance Laboratory [5]. At that time, research was underway to develop high-temperature non-magnetic alloys for missile cone applications. Buehler’s early eforts identifed both the Nitinol 55 and Nitinol 60 alloys, which contain 55 and 60 wt% nickel, respectively. Nitinol 55 is soft and exhibits remarkable shape memory efects, while Nitinol 60 is hard and is also dimensionally stable. Both alloys have apparent elastic modularity, comparable to titanium. Buehler halted work on the hard Nitinol 60 because it was complicated to process and produce. Nitinol 60 also tended to spontane- ously fracture upon cooling after it had been cast [2]. Nowadays, by applying modern powder metallurgy manu- facturing methods, quality bearing balls and races have been routinely produced. This medium has opened the potential for bearings that exhibit excellent corrosion resistance and tribological behaviour [2]. Recent tests, using 60NiTi in col- laboration with Nanotecplasma laboratory at Univap, SP, Brazil, found improved corrosion protection when using amorphous carbon base materials. * L. Vieira lucia.vieira@univap.br 1 Research and Development Institute, IPD/UNIVAP, São José dos Campos, SP, Brazil 2 Technological Institute of Aeronautics, ITA/LPP, São José dos Campos, SP, Brazil 3 University of São Paulo, USP/Polytechnic school, São Paulo, SP, Brazil