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Temperature can have a significant effect on the extent of wear damage of metallic components. Thermal barrier coatings can improve the high temperature tribological and friction wear behavior. In this work the dry friction and wear behavior at low and high temperature of NiCoCrAlY and CoNiCrAlY laser cladding coatings were evaluated, as well as for the austenitic stainless steel AISI 304 used as substrate. Dense coatings, with good bonding to the substrate was obtained by coaxial laser cladding tracks (40% overlapping), with previously optimized laser parameters. Tribological wear tests were performed by sliding wear at room temperature and 500 1C, with an Al2O3 ball on disk configuration tribometer. The wear scar surface was evaluated by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) microanalysis. The 3D topography of the wear track was determined by inductive contact profilometer which enabled the wear rate calculation. The microstructure of the coatings consists of γNi/β-NiAl or γCo/β-(Co,Ni)Al phases depending on the chemical composition of the alloy, as confirmed by X-ray diffraction (XRD) analysis. The wear test results show a reduction in wear rate at high temperature for all materials tested. For the NiCoCrAlY coating, the high temperature also reduces the friction coefficient, while it significantly increases the friction coefficient of CoNiCrAlY coating. The main damage mode is abrasion and adhesion, caused by the oxide and partially-oxidized particles in the contact surface. The coatings and substrate results were compared, resulting in an improved wear behavior.

Degradation mechanisms of biomedical alloys involve two different phenomena, corrosion and wear, which simultaneously act and may cause the failure of implants and prosthesis. In this work, tribocorrosion of Ti6Al4V biomedical alloy in artificial saliva is studied at open circuit potential (OCP) by a new electrochemical technique that allows measuring the galvanic potential and current between the wear track (anode) and the passive material (cathode) through zero-resistance ammetry. The experimental set-up was conceived for physically separating the depassivated area from the passive material, thus allowing to quantify the mechanically activated corrosion at OCP. Two different counterparts, SiC and Al 2 O 3 , were used against the Ti6Al4V alloy in order to analyse the influence of the initial contact pressure on the tribocorrosion mechanisms. A galvanic model based on the cathodic reaction kinetics can describe the current and the potential evolution with time during sliding. It has been observed that at the highest initial contact pressures, wear follows the Archard law, while at lower contact pressures, third body appeared and wear can not be described by the Archard law. Quantification of the evolution of the depassivated wear track with time was obtained and the deviation from the Archard predictions was analysed.