Electrochemical and mechanical behavior of laser processed Ti–6Al–4V surface in Ringer’s physiological solution

Laser surface modification of Ti–6Al–4V with an existing calcium phosphate coating has been conducted to enhance the surface properties. The electrochemical and mechanical behaviors of calcium phosphate deposited on a Ti–6Al–4V surface and remelted using a Nd:YAG laser at varying laser power densities (25–50 W/mm 2 ) have been studied and the results are presented. The electrochemical properties of the modified surfaces in Ringer’s physiolog- ical solution were evaluated by employing both potentio- dynamic polarization and electrochemical impedance spectroscopy (EIS) methods. The potentiodynamic polar- izations showed an increase in the passive current density of Ti–6Al–4V after laser modification at power densities up to 35 W/mm 2 , after which it exhibited a decrease. A reduction in the passive current density (by more than an order) was observed with an increase in the laser power density from 25 to 50 W/mm 2 . EIS studies at the open circuit potential (OCP) and in the passive region at 1.19 V showed that the polarization resistance increased from 8.274 9 10 3 to 4.38 9 10 5 X cm 2 with increasing laser power densities. However, the magnitudes remain lower than that of the untreated Ti–6Al–4V at OCP. The average hardness and modulus of the laser treated Ti–6Al–4V, evaluated by the nanoindentation method, were deter- mined to be 5.4–6.5 GPa (with scatter \±0.976 GPa) and 124–155 GPa (with scatter \±13 GPa) respectively. The corresponding hardness and modulus of untreated Ti–6Al–4V were *4.1 (±0.62) and *148 (±7) GPa respec- tively. Laser processing at power densities [35 W/mm 2 enhanced the surface properties (as passive current density is reduced) so that the materials may be suitable for the bio-medical applications

Sliding Wear Behavior of Al2O3-TiO2 Coatings Fabricated by the Suspension Plasma Spraying Technique

[EN] The friction and dry sliding wear behavior of alumina and alumina-titania near-nanometric coatings were examined. Coatings were obtained by the suspension plasma spraying technique. Dry sliding wear tests were performed on a ball-on-disk tribometer, with an Al2O3 ball as counterpart material, a normal load of 2 N, a sliding distance of 1200 m and a sliding speed of 0.1 m/s. The effect of including TiO2 in the fabricated coatings on friction coefficient behavior, wear rates and wear damage patterns was determined. The addition of TiO2 to the coatings was found to greatly increase wear resistance by, for example, 2.6-fold for 40 wt% of TiO2. 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Tribology of laser modified surface of stainless steel in physiological solution

The laser surface treatment of stainless steel (SS) 316L, an important alloy for biomedical applications, was used to improve its corrosion and wear-corrosion resistance in bio-environment. Microstructural and X-ray diffraction (XRD) pattern analysis showed presence of an austenitic phase in both untreated and laser-treated SS316L. Laser melting produced homogenized and refined microstructure on the surface with higher hardness (143–171 HV) compared to untreated SS316L (131 HV). Increase in intensity of γ (200) peaks in XRD pattern for laser-treated ( > 800 W) SS316L indicated possible crystallographic orientation along γ (200) plane. Passive currents were reduced to + 344 mV for samples laser surface treated at greater than 1200 W. The volume-loss and wear-rate of laser-treated SS316L were significantly reduced compared to untreated sample. Abrasive wear was the main wear mechanism for both untreated and laser surface treated SS316L. Wear particles/debris were found to be cold welded on the surface of SS316L and showed brittle cracking with further wear-straining

Corrosion degradation and prevention by surface modification of biometallic materials

Metals, in addition to ceramics and polymers, are important class of materials considered for replacement of non-functional parts in the body. Stainless steel 316, titanium and titanium alloys, Co-Cr, and nitinol shape memory alloys are the most frequently used metallic materials. These alloys are prone to corrosion in various extents. This review briefly discusses the important biomaterials, their properties, and the physiological environment to which these materials are exposed. Corrosion performance of currently used metallic materials has been assessed and threat to the biocompatibility from corrosion products/metal ions is discussed. The possible preventive measures to improve corrosion resistance by surface modification and to increase the bioactivity of the metallic surfaces have also been discussed. Importance of the formation of oxide layers on the metal surface, another aspect of corrosion process, has been correlated with the host response. The gap areas and future direction of research are also outlined in the paper

Laser Surface Modification of Ti–6Al–4V: Wear and Corrosion Characterization in Simulated Biofluid

Laser surface melting (LSM) of Ti–6Al–4V is performed in argon to improve its properties, such as microstructure, corrosion, and wear for biomedical applications. Corrosion behavior is investigated by conducting electrochemical polarization experiments in simulated body fluid (Ringer’s solution) at 37 C. Wear properties are evaluated in Ringer’s solution using pin-on-disc apparatus at a slow speed. Untreated Ti–6Al–4V contains þ phase. After laser surface melting, it transforms to acicular embedded in the prior matrix. Grain growth in the range of 65–89 mm with increase in laser power from 800 to 1500 W due to increase in associated temperature is observed. The hardness of as-laser- processed Ti–6Al–4V alloy is more (275–297 HV) than that of the untreated alloy (254 HV). Passivation currents are significantly reduced to <4.3 mA/cm2 after laser treatment compared to untreated Ti–6Al–4V (12 mA/cm2). The wear resistance of laser-treated Ti–6Al–4V in simulated body fluid is enhanced compared to that of the untreated one. It is the highest for the one that is processed at a laser power of 800 W. Typical micro-cutting features of abrasive wear is the prominent mechanism of wear in both untreated and as-laser-treated Ti–6Al–4V. Fragmentation of wear debris assisted by microcracking was responsible for mass loss during the wear of untreated Ti–6Al–4V in Ringer’s solution

Influence of laser surface modification on corrosion behavior of stainless steel 316L and Ti-6Al-4V in simulated biofluid

Laser surface engineering has been explored as a possible method for improving the functional surface properties of biomedical materials such as stainless steels and titanium alloys. This study emphasises the influence of laser surface processing, carried out at a range of laser powers from 500 to 1500 W in ambient atmosphere, on the surface microstructure and corrosion behaviour of stainless steel 316L (SS316L) and Ti-6Al-4V, and metal ions released during the corrosion process. A homogeneous surface microstructure includes columnar dendrites and fine grains in the resolidified region of SS316L. A gradual increase in grain size from the processed surface towards the substrate was revealed, The laser processing of Ti-6Al-4V produced a surface full of dendrites followed by acicular martensite in the interface region. The corrosion studies in Ringer's physiological solution showed an increase in the open circuit potential (OCP) as a result of laser surface treatment of both SS316L and Ti-6Al-4V (more noble than untreated). After laser processing, the corrosion properties of SS316L were seen to deteriorate, and those of Ti-6Al-4V to improve, as compared to their respective untreated counterparts. The variation of laser power influenced the corrosion resistance of SS316L, while that of Ti-6Al-4V did not vary significantly. Laser surface treatments at higher powers (> 1000 W) reduced the leaching of specific metallic ions from SS316L and Ti-6Al-4V during corrosion in Ringer's physiological solutio