Topographic and Electrochemical Ti6Al4V Alloy Surface Characterization in Dry and Wet Reciprocating Sliding

This present paper shows the behavior of functional integrity of the state Ti6Al4V alloy under reciprocating sliding wear conditions in acomparative way for two different counter materials, steel and ceramicballs in dry and corrosive environment (3.5% NaCl). The surface integrity analysis of the dry reciprocating wear tests was based on the evolution of The roughness parameters with the applied load. In the case of reciprocating wear tests in corrosive environment the surface integrity analysis was based on electrochemical parameters. Comparative analysis of the evolution of the roughness parameters with the applied load shows a higher stability of the Ti6Al4V/Al2O3 contact pair, while from the point of view of the electrochemical parameters the Tribological properties are worse than Ti6Al4V/steel ball contact pair

Multi-material Ti6Al4V & PEEK cellular structures produced by Selective Laser Melting and Hot Pressing: A tribocorrosion study targeting orthopedic applications

This work was supported by FCT through the grants SFRH/BD/128657/2017 and SFRH/BPD/112111/2015, the project PTDC/EMSTEC/5422/2014 and also by project NORTE 01–0145_FEDER-000018. Additionally, this work was supported by FCT with the reference project UID/EEA/04436/2013, by FEDER funds through the COMPETE 2020 – Programa Operacional Competitividade e Internacionalização (POCI) with the reference project POCI-01–0145-FEDER-006941.Ti6Al4V-alloy is commonly used in dental and orthopedic applications where tribochemical reactions occur at material/bone interface. These reactions are one of the main concerns regarding Ti6Al4V implants due to the generation of wear particles, linked to the release of metallic ions in toxic concentration which occurs when TiO2 passive film is destroyed by means of wear and corrosion simultaneously. In the present study, a multi-material Ti6Al4V-PEEK cellular structure is proposed. Selective Laser Melting technique was used to produce Ti6Al4V dense and cellular structured specimens, whilst Hot-Pressing technique was employed to obtain multi-material Ti6Al4V-PEEK structures. This study investigates the tribocorrosion behavior of these materials under reciprocating sliding, comparing them with commercial forged Ti6Al4V. Open-circuit-potential was measured before, during and after sliding while dynamic coefficient of friction was assessed during sliding. The results showed an improved wear resistance and a lower tendency to corrosion for the multi-material Ti6Al4V-PEEK specimens when compared to dense and cellular structures mono-material specimens. This multi-material solution gathering Ti6Al4V and PEEK, besides being able to withstand the loads occurring after implantation on dental and orthopedic applications, is a promising alternative to fully dense metals once it enhances the tribocorrosion performance.info:eu-repo/semantics/publishedVersio

Tribocorrosion behaviour of hot pressed CoCrMo−Al2O3 composites for biomedical applications

Alumina/alumina wear couple can lower the wear rates and thus metallic ion releasing on load bearing metallic implant materials. However, the low fracture toughness of ceramics is still a major concern. Therefore, the present study aims to process and to triboelectrochemically characterise the 5 and 10 vol.-%Al2O3 reinforced CoCrMo matrix composites. Corrosion and tribocorrosion behaviour of the composites were investigated in 8 g L21 NaCl solution at body temperature. Corroded and worn surfaces were investigated by a field emission gun scanning electron microscope equipped with energy dispersive X-ray spectroscopy. After tribocorrosion experi- ments, wear rates were calculated using a profilometer. Results suggest that Al2O3 particle addition decreased the tendency of CoCrMo alloy to corrosion under both static and tribocorrosion conditions. However, no significant influence on the corrosion and wear rates was observed in composites mainly due to increased porosity and insufficient matrix/ reinforcement bonding.This study was supported by the Portuguese Foundation for Science and Technology (FCT-Portugal), under project no. EXCL/EMS-TEC/0460/2012, and The Calouste Gulbenkian Foundation through 'Programa de Mobilidade Academica para Professores'. The authors also would like to thank Professor A. Ramalho (Universidade de Coimbra) for the provision of profilometry facilities

Ti6Al4V cellular structures impregnated with biomedical PEEK: New material design for improved tribological behavior

This work was supported by FTC through the grant SFRH/BPD/112111/2015 and the project PTDC/EMS-TEC/5422/2014. Additionally, this work was supported by the project NORTE 01–0145_FEDER-000018 and by FCT with the reference project UID/EEA/04436/2013, by FEDER funds through the COMPETE 2020 – Programa Operacional Competitividade e Internacionalizaç~ao (POCI) with the reference project POCI-01-0145-FEDER-006941.In the present work, a new material design of Ti6Al4V-PEEK hybrid cellular structure with improved wear resistance is proposed. Samples with different dimensions of the open-cells (350, 400, 450, 500 μm) were fabricated by Selective laser melting (SLM) technology, while Hot pressing (HP) technology was employed to produce Ti6Al4V-PEEK hybrid cellular structures. The tribological tests were performed in Phosphate Buffered Saline solution at 37 ± 2 C. Results demonstrated that the addition of the biomedical PEEK protected the Ti6Al4V cellular structures, thus improving these hybrid structures wear resistance when increasing the amount of PEEK. The obtained results indicated that the Ti6Al4V-PEEK hybrid cellular structure with the dimensions of the opencells of 500 μm is a suitable structure for orthopedic implants, with improved properties.info:eu-repo/semantics/publishedVersio

Laser surface structuring of Ti6Al4V substrates for adhesion enhancement in Ti6Al4V-PEEK joints

PEEK is a promising polymer possessing high mechanical strength and biocompatibility and therefore it can be associated to titanium for biomedical applications. This study aimed at producing Ti6Al4V-PEEK joints with enhanced adhesion through laser-structuring Ti6Al4V treatments. Ti6Al4V cylindrical substrates were prepared by two types of surface treatments: alumina blasting and laser structuring. The holes number and size in laserstructured surfaces was varied. PEEK was then hot pressed against the metallic substrate to completely filling the surface cavities. The adhesion of the PEEK/Ti6Al4V joint was assessed by a shear bond strength test. Fracture surfaces and interfaces were investigated by SEM/EDS. Significant differences were found in the shear bond strength between alumina blasted and laser-structured samples. Bond strength improvement (exceeding 300%) was registered for the laser-structured specimens relative to grit-blasted ones. The laser-structuring technique showed to be very promising in the production of specifically designed surfaces for high strength andmechanically stable Ti6Al4V/PEEK joints.This work has been supported by FCT (Fundação para a Ciência e Tecnologia - Portugal) in the scope of the projects UID/EEA/04436/2013, EXCL/ EMSTEC/0460/2012 and NORTE-01-0145-FEDER-000018 – HAMaBICo.info:eu-repo/semantics/publishedVersio

Comparison between PEEK and Ti6Al4V concerning micro-scale abrasion wear on dental applications

In the oral cavity, abrasive wear is predictable at exposed tooth or restorative surfaces, during mastication and tooth brushing. Also, wear can occur at contacting surfaces between theTi-based prosthetic structures and implants in presence of abrasive compounds from food or tooth paste. Thus, the aim of this work was to compare the abrasive wear resistance of PEEK and Ti6Al4V on three-body abrasion related to different hydrated silica content and loads. Surfaces of Ti6Al4V or PEEK cylinders (8 mm diameter and 4mm height) were wet ground on SiC papers and then polished with 1 mm diamond paste. After that, surfaces were ultrasonically cleaned in propyl alcohol for15 min and then indistilled water for 10 min. Micro-scale abrasion tests were performed at 60 rpm and on different normal loads (0.4, 0.8 or 1.2 N) after 600 ball revolutions using suspensions with different weight contents of hydrated silica. After abrasive tests, wear scars on flat samples were measured to quantify the wear volume and characterized by scanning electron microscope (SEM) to identify the dominant wear mechanisms. Results showed a higher volume loss rate on PEEK than that recorded on Ti6Al4V, when subjected to three-body abrasion tests involving hydrated silica suspensions. An increase in volume loss was noted on both tested materials when the abrasive content or load was increased. PEEK was characterized by less wear resistance than that on Ti6Al4V after micro-scale abrasion wear in contact with hydrated silica particles, as commonly found in toothpastes.This work has been supported by FCT (Fundacao para a Ciencia e Tecnologia - Portugal) in the scope of the project UID/EEA/04436/2013 and EXCL/EMS-TEC/0460/2012.info:eu-repo/semantics/publishedVersio

Effects of poly-ether-ether ketone (PEEK) veneer thickness on the reciprocating friction and wear behavior of PEEK/Ti6Al4V structures in artificial saliva

Poly-ether-ether-ketone (PEEK) veneers are attractive materials for biomedical contacting surfaces. In the present study, PEEK veneers with thicknesses between 0.1 and 2 mm were synthesized on Ti6Al4V substrates by hot pressing. The influence of PEEK thicknesses on the friction and wear behavior of veneering PEEK to Ti6Al4V structures was studied under reciprocating sliding conditions against an alumina counterbody immersed in artificial saliva at 37 °C. Additionally, numerical simulations were carried out to evaluate the influence of PEEK thickness on the contact stress. Theresults revealed that the coefficient of friction and the wear rate increased with decreasing the PEEK thickness. It was revealed that the increase of both coefficient of friction and wear rate are correlated with increased contact stress level on PEEK veneer. Such factors are determinant on the long term success of veneering biomedical PEEK to Ti6Al4V for oral applications.This work has been supported by FCT (Fundação para a Ciência e Tecnologia – Portugal) in the scope of the project UID/EEA/ 04436/2013 and EXCL/EMSTEC/0460/2012.info:eu-repo/semantics/publishedVersio

Abrasive and sliding wear of resin composites for dental restorations

The aim of this work was to study the abrasive and reciprocating sliding wear resistance of four commercial resin composites for dental restorations. Resin composite samples were divided into four groups considering the different materials and then separated for compressive, abrasive and sliding tests (n=10). Micro-abrasion tests were performed against a stainless steel rotating ball on 3 N normal load for 300 revolutions in the presence of a suspension containing a commercial whitening and abrasive tooth paste. Reciprocating sliding ball-on-plate friction tests were performed against an alumina ball on 20 N normal load at 1 Hz in the presence of artificial saliva at 37 °C for 30 min.The wear volume was evaluated for the different groups of resin composites and correlated with their mechanical properties and inorganic composition in terms of size and volume percentage of filler particles. Resin composites with high volume content of inorganic fillers (82 wt%) consisting of microparticles( 0.1–2.5 μm) combined with small nanoparticles (20–60 nm) revealed the most proper mechanical and tribological response. The dominant wear mechanisms consisted on fine micro-scale abrasion for abrasion tests and surface fatigue and abrasion for reciprocating sliding tests.This work has been supported by FCT (Fundação para a Ciência e Tecnologia -Portugal) in the scope of the project UID/EEA/04436/ 2013 and EXCL/EMS-TEC/0460/2012.info:eu-repo/semantics/publishedVersio