Wear of elements subjected to friction and sliding is among the main causes of low tribological performance and short lifetime of strategic materials such as titanium alloys. These types of alloys are widely used in different areas such as aerospace and the biomechanics industry. In this sense, surface modification treatments allow for the overcoming of limitations and improvement of features and properties. In the case of titanium alloys, improvements in the main weaknesses of these materials can be obtained. Laser texturing of UNS R56400 (Ti6Al4V) alloy, according to Unified Numbering System designation, surface layers in a non-protective atmosphere produces an increase of the oxides, especially of titanium dioxide (TiO2) species. The presence of oxides in the alloy results in color tonality variations as well as hardness increases. In addition, specific roughness topographies may be produced by the track of laser beam irradiation. In this research, thermochemical oxidation of UNS R56400 alloy has been developed through laser texturing, using scan speed of the beam (Vs) as the process control variable, and its influence on the sliding wear behavior was analyzed. For this purpose, using pin on disc tribological tests, wear was evaluated from the friction coefficient, and wear mechanisms involved in the process were analyzed. Combined studies of wear mechanisms and the friction coefficient verified that by means of specific surface treatments, an increase in the wear resistance of this type of alloys is generated. The most advantageous results for the improvement of tribological behavior have been detected in textured surfaces using a Vs of 150 mm/s, resulting in a decrease in the friction coefficient values by approximately 20%.

Surface engineering is widely used in different areas, such as the aerospace industry or the biomechanical and medical fields. Specifically, laser surface modification techniques may obtain specific surface finishes for special applications. In texturing laser procedures, the control of processing parameters has a great influence on the geometry and characteristics of the treated area. When these processes are carried out on titanium alloys, thin oxide layers are usually developed on the irradiated surface, formed through the thermochemical combination of vaporized material with atmospheric oxygen in the air. In thermal oxidation treatments of Ti6Al4V, the highest concentration of oxides is mainly composed by rutile (TiO 2 ), producing surface property modifications such as hardness, among others. In this research, a thermochemical oxidation of Ti6Al4V alloy has been performed through laser texturing, using laser scanning speed (V s ) and pulse rate (f ) as process control variables, and its influence on the beam absorption capacity of the modified layer have been analyzed. Combined evaluations of microgeometrical features and mechanical properties, such as hardness, verified that, by means of laser texturing treatments, the ability to generate specific topographies and increase the initial hardness of the alloy is obtained. The most advantageous results for the increase of hardness by thermochemical oxidation have been detected in low scan speeds of laser beam treatments, resulting in an increase of approximately 270% using a scanning speed of 10 mm/s. On the other hand, a dependence between roughness values, in terms of R a and R z , and the energy density of pulse (E d ) has been observed, showing higher values of roughness for a 17.68 J/cm 2 energy density of pulse.

Ti-5Al-5V-5Mo-3Cr (Ti5553) is a metastable β titanium alloy with a high potential use in the aeronautic industry due to its high strength, excellent hardenability, fracture toughness and high fatigue resistance. However, recent research shows this alloy has a limited weldability. Different welding technologies have been applied in the literature to weld this alloy, such as electron beam welding (EBW), gas tungsten arc welding (GTAW) or laser beam welding (LBW) under keyhole regime. Thus, in tensile tests, joints normally break at the weld zones, the strength of the welds being always lower than that of the base metal. In the present work, a novel approach, based on the application of LBW under conduction regime (with a High-Power Diode Laser, HPDL), has been employed for the first time to weld this alloy. Microstructure, microhardness and strength of obtained welds were analyzed and reported in this paper. LBW under conduction regime (LBW-CR) leads to welds with slightly higher values of Ultimate Tensile Strength (UTS) than those previously obtained with other joining processes, probably due to the higher hardness of the fusion zone and to lower porosity of the weld.

The selection of appropriate surface pretreatments is one of the pending issues for the industrial application of cerium-based chemical conversion coatings (CeCC) as an alternative for toxic chromate conversion coating (CrCC). A two-step surface pretreatment based on commercial products has been successfully used here to obtain CeCC on AA2024-T3 and AA7075-T6. Specimens processed for 1 to 15 min in solutions containing CeCl3 and H2O2 have been studied by scanning electron microscopy coupled with energy-dispersive X-ray analysis (SEM-EDX), glow discharge optical emission spectroscopy (GDOES), potentiodynamic linear polarization (LP), electrochemical impedance spectroscopy (EIS), and neutral salt spray (NSS) tests. SEM-EDX showed that CeCC was firstly observed as deposits, followed by a general coverage of the surface with the formation of cracks where the coating was getting thicker. GDOES confirmed an increase of the CeCC thickness as the deposition proceed, the formation of CeCC over 7075 being faster than over 2024. There was a Ce-rich layer in both alloys and an aluminum oxide/hydroxide layer on 7075 between the upper Ce-rich layer and the aluminum matrix. According to LP and EIS, CeCC in all samples offered cathodic protection and comparable degradation in chloride-containing media. Finally, the NSS test corroborated the anti-corrosion properties of the CeCC obtained after the commercial pretreatments employed.

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