Bioactive glass S520 laser cladding on ultrafine-grained pure titanium substrates

Nowadays, titanium alloys are commonly used for different biomedical applications instead of pure titanium because of their superior mechanical properties. Presence of some alloying elements, such as aluminium and vanadium, can be harmful to human health, and can be considered as disadvantage in long term applications. Potentially, there is a possibility of replacing the commercial titanium alloys with ultrafine-grained commercially pure Ti (cpTi). The yield and ultimate strength of cpTi can exceed 1000 MPa [1]. When manufacturing medical devices, laser cladding is known as one of the most promising methods for manufacturing of modern medical implants with improved osseointegration, where bioactive glass coatings are imposed on metallic substrates [2, 3]. Experimental Methods: In this work, S520 bioactive glass was imposed on ultrafine-grained cpTi using laser cladding technique. Cross-sectional SEM images of titanium substrate and bioactive glass were analyzed. The interface between bioactive glass and metallic titanium substrate was also studied using SEM/EDX. Results and Discussion: The refined microstructure of cpTi was locally modified in the areas affected by the laser beam. Figure 1 shows the cross-section of the ultrafine-grained cpTi substrate after the laser cladding process. The cross-section of the cladded bioactive glass is presented in figure 2. Some pores of up to 200 µm diameter were found within. Conclusion: The S520 bioactive glass was successfully cladded onto the ultrafine-grained cpTi substrate. The application of cpTi allows for exclusion of potential toxic elements from the human body and its refined microstructure allows to achieve strength properties similar to those of Ti6Al4V alloy

Characterization of nanocrystallised multilayered metallic materials produced by the SMAT followed by constrained compression

Nanocrystallised multilayered metallic material was obtained via duplex technique combining the surface mechanical attrition treatment (SMAT) with a novel constrained compression (CC) process. At the initial stage the 1 mm thick sheets of 316L austenitic stainless steel were processed by the SMAT in order to form a nanocrystalline structure. At the final stage disc-shaped plates excised from SMATed sheets, were assembled in a package and compressed in order to produce metallurgical bonding between individual plates. The characterization of such a multilayered structure was studied both experimentally and numerically. The microscopic examination revealed that the bonding occurred in the central portions of the package where the oxide scale covering each plate was fragmented by high shear strains. The numerical analysis confirmed that the strains at the interior interfaces are significantly higher than at the external ones. A high degree of structural inhomogeneity was observed via TEM studies in the regions where the successful bonding was achieved. Regions characterised by fine band structure with the presence of α′-martensite phase as well as coarse cellular structure within a single γ-austenite phase were identified

Impact of the Direct Ageing Procedure on the Age Hardening Response of Al-Mg-Si 6101 Alloy

Al-Mg-Si alloys are used not only as construction material, but also as a material for electrical conductors. For this application, it is crucial for the alloy to achieve a balance between strength and electrical properties. This is achieved in practice by a combination of strain and precipitation hardening. The current paper focuses on a heat treatment procedure in which the EN AW 6101 alloy is cooled by a flowing air stream from the solutionizing temperature down to the artificial ageing temperature. The proposed procedure, unlike the common heat treatment leading to the T6 temper, allowed for the precipitation of the coarser β” phase with the presence of relatively wide precipitate-free zones. The age hardening response was investigated by Brinell hardness measurements, eddy current testing and microstructural observations using transmission electron microscopy (TEM). The applied heat treatment resulted in slightly lower strength (compared to the T6 temper), but improved electrical performance of the alloy

Microstructural characterization of nanostructured supersonic sprayed Ni-Sn coatings after wear tests at elevated temperature

The paper presents results of the wear behavior, as well as the microstructural (scanning and transmission electron microscopy) and compositional (microanalysis with using energy dispersive and X-ray photon emission spectroscopy) characterization of nanostructured Ni-20Sn (wt.%) coatings, deposited on an Inconel 718 substrate by supersonic cold gas spraying at different spraying parameters. Coatings were examined in the as-deposited state and after testing in a linearly reciprocating sliding wear test at room temperature, 200, 400 and 550 °C. It was found that the Ni–Sn coatings exhibit superior wear resistance compared to benchmark materials. This is attributed to an appropriate balance of soft (Ni) and to hard (Ni3Sn – intermetallic) phases and to the nanostructure of the matrix, as well as to the presence of an NiO oxide tribo-layer, as revealed by the microanalysis and electron microscopy Read More: http://www.hanser-elibrary.com/doi/abs/10.3139/146.111244status: publishe

Laser cladding of bioactive glass coating on pure titanium substrate with highly refined grain structure

Free from toxic elements biomaterial potentially applicable for load bearing biomedical implants was obtained for the first time by laser cladding of S520 bioactive glass onto ultrafine-grained commercially pure titanium. The cladding process affected the refined structure of the substrate inducing martensitic transformation near its surface. The α’ acicular martensite gradually passes into relatively large grains with increasing distance from the substrate surface, which subsequently are transformed into smaller grains of about 2 μm in diameter. Both the melted zone, where the martensite crystalline structure was found, and the HAZ are characterized by relatively lower hardness in comparison with that of the substrate core indicating increased ductility. Such a combination of zones with different properties may have a synergistic effect and is beneficial for the obtained biomaterial. A characteristic region in the form of about 3 µm width band was formed in the melted zone at about 10 µm below the titanium surface. The results of EDS analysis indicate that several glass elements moved into the region while the titanium content in the same area was decreased. High bioactivity of the coated S520 glass was revealed by in vitro testing with SBF solution and almost complete reduction of P concentration occurred after 14 days