Effect of CeO2 and Y2O3 on microstructure, bioactivity and degradability of laser cladding CaO–SiO2 coating on titanium alloy

Effect of Y2O3 Addition on Microstructure and Properties of Laser Cladded Al-Si Coatings on AZ91D Magnesium Alloy

The effect of Y₂O₃ addition on the microstructure and properties of the laser cladded Al-Si alloy coating on the surface of AZ91D magnesium alloy was investigated in this study. The experimental results showed that the Al-Si + Y₂O₃ cladding layers contained α-Mg, Mg₂Si, Al₄MgY and a small amount of Al₁₂Mg₁₇ phases. The coarse dendrites, reticulated eutectic structures and massive phases in the coatings tended to be refined and gradually uniformly distributed with the increased amount of Y₂O₃. The introduction of Y₂O₃ into the cladding layer favored the improvement of microhardness and wear resistance due to the grain refinement strengthening and dispersion strengthening. The addition of Y₂O₃ also promoted the reduction of localized corrosion sites and made the corrosion surface smoother, implying that the corrosion resistance of the Y₂O₃-modified coatings was better than that of the unmodified cladding layer.

Effects of La2O3contents on microstructure and properties of laser-cladded 5wt%CaB6/HA bioceramic coating

In the present work, 5wt%CaB6/HA bioceramic coatings with different La2O3contents (0-0.6wt%) have been fabricated by a laser cladding technique on Ti-6Al-4V. The effects of La2O3 contents on microstructure and properties of the laser-cladded 5wt%CaB6/HA coatings have been carefully investigated. The results show that the microstructure is obviously refined, and the structure is relatively uniform after doping 0.2-0.4 wt% La2O3. As the La2O3 content increases, the corrosion resistance are found to increase firstly and then gradually decrease. The XRD analysis confirms that the amount of HA and TCP in the coating reaches maximum after doping 0.2wt% La2O3. The La2O3-doped coatings show a significantly higher bone-like apatite precipitation after immersion in SBF compared with La2O3-free coating. In vitro experiment also shows that 5wt%CaB6/HA bioceramic coatings with 0.2-0.4wt% La2O3 are more suitable for the attachment and proliferation of MG63 cells, exhibiting superior bioactivity and biocompatibility.

Effect of Na2O and ZnO on the microstructure and properties of laser cladding derived CaO-SiO2 ceramic coatings on titanium alloys

To improve the bioactivity of titanium alloy (Ti-6Al-4V), CaO-SiO₂ coatings on titanium alloys were fabricated using laser cladding method. The effect of Na₂O and ZnO on the microstructure and properties of the prepared coatings was discussed. The microstructure of the CaO-SiO₂ coatings consists of cellular grains and cellular dendrites. The mutual diffusion of elements occurs between the coating and substrate. The base CaO-SiO₂ coating is composed of different phases including CaTiO₃, α-Ca₂(SiO₄), SiO₂, TiO₂ and CaO. The formation of CaTiO₃ in the ceramic layer was analyzed through thermodynamics. Na₂O has little influence on the microstructure, average hardness and wear resistance. When ZnO is added to the precursor, the microstructure turns to cell dendrite, and ZnO and Zn₂SiO₄ appear in the corresponding coating. The addition of ZnO reduces the average hardness and wear resistance of the ceramic layer. The in vitro soaking in SBF shows that the laser cladding coating has the ability to form an apatite layer.

ZrxCa30-xP70 thermoluminescent bio glass, structure and elasticity

Phosphate glasses of calcium oxide have been well proved materials for various bio bones and dental implants. However, still there is a lot of scope and demand to produce efficient elastic bio implants and resource. In view of this, Zr_xCa_30-xP₇₀ phosphate materials are prepared by using melt quenching method. Bio, physical, thermoluminescence and elastic techniques are used to characterize the samples. Additionally, simulated body fluid was prepared and it is used especially for bio techniques. Further, the glasses are taken for different dose (~0, 10, 20 & 50 kGy) of gamma irradiation around half an hour. And again similar techniques are used to characterize the samples. All the findings from bio, physical, thermoluminescence and elastic characterization results are analysed and took for better comparison with previous studies to develop various bio bone (or) bio dental resource. Structural reports suggests that the Zr_xCa_30-xP₇₀ materials were glassy before immersion in SBF solution and immersed (~720 h) samples are showing partial ceramic nature. The weight loss and pH reports suggests them for alternative bio resource as a bio bones and dental implants. Observed thermal stability, microhardness and elastic modulus evaluations of Zr_xCa_30-xP₇₀ materials in required standards are also additional advantage. Furthermore, thermoluminiscence (TL) under different γ-irradiation doses is reported for glasses with and without immersing in a simulated body fluid. The glasses lose TL intensity when immersed in simulated body fluid for nearly 720 h. This is useful to modulate bio-behaviour in terms of hydroxyapatite layer growth on the glass surface.

Effect of doping different Si source on Ca-P bioceramic coating fabricated by laser cladding

The doping of silicon (Si) has been proved to improve the bioactivity of Ca-P ceramics. In light of this thinking, in the present study, Ca-P coatings with La₂O₃ by addition of 10 wt% SiO₂ and 10 wt% diatomaceous earth (DE) were fabricated by laser cladding on Ti6Al4V, respectively. Coating doped without Si was also fabricated as the comparison group for the experiment. The effect of two different Si sources on the surface morphology, microstructure, microhardness, and bioactivity was systematically studied. The experimental results show that the Si-doped coating is of rough surface morphology, and the addition of DE significantly reduces the number of cracks and improves the microhardness. The X-ray diffraction results reveal that the amount of bioactive phase tricalcium-phosphate (TCP) and hydroxyapatite (HA) reaches maximum in the DE-doped coating. After soaking in simulated body fluid (SBF), the precipitate of bone-like apatite in the DE-doped coating is significantly higher than that of the other coatings.

Laser Cladding of Al0.5CoCrCuFeNiSi High Entropy Alloy Coating without and with Yttria Addition on H13 Steel

Al0.5CoCrCuFeNiSi high entropy alloy coating without and with a 1 wt.% Y2O3 addition was fabricated by laser cladding technique on H13 substrate. The results showed that the laser cladding coatings without and with Y2O3 addition consist of a mixture of body centered cubic (BCC) dendrites and face centered cubic (FCC) interdendrites. With the addition of Y2O3, the peaks of BCC dendrites in the coating shifted to leftwards, which is caused by the distortion of lattice due to the dissolution of Y with larger atomic radius. There exist cracks and porosities in the coating without Y2O3 addition. With Y2O3 addition, the cracks and porosities in the laser cladding coating were inhibited greatly. In addition, the microstructure of the coating with Y2O3 addition was refined due to the improving of the ratio of nucleation. The enhancement of properties, such as hardness, wear resistance and corrosion resistance, of the coating with Y2O3 addition came from the inhibition of cracks and porosities and the refinement of microstructure.

Study on microstructure, microhardness, bioactivity, and biocompatibility of La2 O3 -containing bioceramic coating doping SiO2 fabricated by laser cladding

To solve the lack of strength of calcium phosphate ceramic coatings in load-bearing applications, gradient Ca-P bioceramic coatings doped with La₂ O₃ and SiO₂ are fabricated by laser cladding on Ti-6Al-4 V. The effect of SiO₂ on microstructure, microhardness, bioactivity, and biocompatibility of coatings was investigated. The experimental results illustrate that the coating doped with La₂ O₃ and SiO₂ has excellent metallurgical bonding. The XRD analysis confirms that the amount of hydroxyapatite and tricalcium phosphate in the coating reached maximum when doping amount of SiO₂ is 10 wt %. SiO₂ -doped coatings show a significantly higher bone-like apatite precipitation after immersion in SBF than that of other coatings. in vitro experiment also shows that coating with 10 wt % SiO₂ is more suitable for the attachment and proliferation of MG63 cells, indicating that coating with 10 wt % SiO₂ exhibits best bioactivity and biocompatibility. These results suggest that the addition of SiO₂ improves the bonding strength, bioactivity, and biocompatibility of coatings.

Laser Cladding of Ti-Based Ceramic Coatings on Ti6Al4V Alloy: Effects of CeO2 Nanoparticles Additive on Wear Performance

Ti-based ceramic coatings on Ti6Al4V substrates were successfully prepared through a laser cladding process using pre-placed starting materials of TiCN + SiO2 mixed powder without or with adding a 3 wt % CeO2 nanoparticles additive, aiming at improving the wear resistance of the Ti6Al4V alloy for biological applications. The effects of the CeO2 nanoparticles additive on the microstructure, microhardness, and wear performance of the coatings were analyzed in detail. The observations showed that the main compositions of the cladding coating were TiCN and TiN phase. Compared to the coatings without CeO2, the coatings modified with CeO2 nanoparticles led to more excellent mechanical properties. The average microhardness of the coatings modified with CeO2 nanoparticles was approximately 1230 HV0.2, and the wear volume loss of the coatings modified with CeO2 nanoparticles was approximately 14% less than that of the coatings without CeO2 under a simulated body fluid (SBF) lubrication environment. The major reasons included that the microstructure of the coatings modified with CeO2 nanoparticles was refined and compact granular crystalline. The wear mechanisms of the coatings were investigated from the worn surface of the coatings, wear debris, and the worn surface of the counter-body balls. The wear mechanisms of the coatings without CeO2 included abrasive wear, adhesive wear, and fatigue wear, while the wear mechanisms of the coatings modified with CeO2 nanoparticles included only abrasive wear and adhesive wear, because the fine microstructure of the coatings had an excellent resistance to fatigue wear.

Effect of CeO₂ on Microstructure and Wear Resistance of TiC Bioinert Coatings on Ti6Al4V Alloy by Laser Cladding

To solve the lack of wear resistance of titanium alloys for use in biological applications, various prepared coatings on titanium alloys are often used as wear-resistant materials. In this paper, TiC bioinert coatings were fabricated on Ti6Al4V by laser cladding using mixed TiC and ZrO₂ powders as the basic pre-placed materials. A certain amount of CeO₂ powder was also added to the pre-placed powders to further improve the properties of the TiC coatings. The effects of CeO₂ additive on the phase constituents, microstructures and wear resistance of the TiC coatings were researched in detail. Although the effect of CeO₂ on the phase constituents of the coatings was slight, it had a significant effect on the microstructure and wear resistance of the coatings. The crystalline grains in the TiC coatings, observed by a scanning electron microscope (SEM), were refined due to the effect of the CeO₂. With the increase of CeO₂ additive content in the pre-placed powders, finer and more compact dendrites led to improvement of the micro-hardness and wear resistance of the TiC coatings. Also, 5 wt % content of CeO₂ additive in the pre-placed powders was the best choice for improving the wear properties of the TiC coatings.

Effect of phosphate additives on the microstructure, bioactivity, and degradability of microarc oxidation coatings on Mg-Zn-Ca-Mn alloy

Calcium phosphate coatings were prepared on the surface of self-designed Mg-Zn-Ca-Mn alloy using microarc oxidization technology. To characterize the microstructures, cross-section morphologies, and compositions of the coatings, the authors used scanning electron microscopy equipped with an energy-disperse spectrometer, x-ray diffraction, and Fourier transform infrared spectroscopy. Potentiodynamic polarization in the simulated body fluid (SBF) was used to evaluate the corrosion behaviors of the samples. An SBF immersion test was used to evaluate the coating bioactivity and degradability. After the immersion tests, some bonelike apatite formed on the coating surfaces indicate that bioactivity of the coatings is excellent. The coating prepared in electrolyte containing (NaPO3)6 had slower degradation rate after immersion test for 21 days.

Preparation and characterization of laser cladding wollastonite derived bioceramic coating on titanium alloy

The bioceramic coating is fabricated on titanium alloy (Ti6Al4V) by laser cladding the preplaced wollastonite (CaSiO3) powders. The coating on Ti6Al4V is characterized by x-ray diffraction, scanning electron microscopy coupled with energy dispersive spectroscopy, and attenuated total reflection Fourier-transform infrared. The interface bonding strength is measured using the stretching method using an RGD-5-type electronic tensile machine. The microhardness distribution of the cross-section is determined using an indentation test. The in vitro bioactivity of the coating on Ti6Al4V is evaluated using the in vitro simulated body fluid (SBF) immersion test. The microstructure of the laser cladding sample is affected by the process parameters. The coating surface is coarse, accidented, and microporous. The cross-section microstructure of the ceramic layer from the bottom to the top gradually changes from cellular crystal, fine cellular-dendrite structure to underdeveloped dendrite crystal. The coating on Ti6Al4V is composed of CaTiO3, CaO, α-Ca2SiO4, SiO2, and TiO2. After soaking in the SBF solution, the calcium phosphate layer is formed on the coating surface.