查看更多>>摘要：In this study, different surface textures (Diamond, Cylinder, and Sin) have been designed and produced on Ti6Al4V alloys by selective laser melting technology. TiO2/Ag composite coatings were prepared on these textures by merging anodic oxidation and spray deposition methods. Tightly arranged TiO2 nanotubes (TNTs) with tube diameters of about 100 nm are found on the top and lateral sides of the textures. On the bottom of the textures, dense nanopores were found with a pore diameter of about 50 nm. Compared with the untreated titanium alloy surface, both texture and TNTs structures would endow the titanium alloy surfaces with higher in vitro bioactivity. All three textures have an enhanced antibacterial property and a complete bactericidal effect was achieved by spray deposition of Ag nanoparticles (AgNPs) on all the surfaces. The MC3T3-E1 cells can adhere to the surfaces and proliferate normally, indicating good cytocompatibility of TiO2/Ag surfaces. Besides, the deposited AgNPs have been found to promote cell proliferation.
查看更多>>摘要：Al2O3 nanoparticles incorporated NiCoW ternary alloy coatings were synthesized by direct current electrode-position from sulphate-citrate electrolyte. The influence of applied current density and electrolyte composition on the evolution of surface morphology, element composition, microstructure, microhardness and sliding wear behavior of the as-deposited coatings was investigated. The as-deposited coatings exhibit colony surface morphology and the inter-colony boundaries lead a leaf vein-like cross-sectional structure. The composition of the as-deposited coatings is controlled by the induced co-deposition mechanism and the competition among the reductions of Ni, Co, Ni-W and Co-W. The as-deposited coatings change from crystalline to amorphous structure with the decrease of Ni content in coatings and the critical Ni content for the transformation is about 40 at.%. The incorporation of Al2O3 nanoparticles leads to a little increase of microhardness, degrades adhesive wear and oxidation wear, then significantly improve wear resistance. Variations in electrodeposition conditions lead the as-deposited coatings with different wear behavior, including abrasive wear, adhesive wear and oxidation wear, accompanying with plastic deformation. An attempt is made to establish the relationship between the electro-deposition conditions and wear behavior.
Schuette, Waynie M.Brewer, Luke N.Perez-Andrade, Lorena I.Bhattiprolu, Venkata Satish...
10页
查看更多>>摘要：This paper studies the microstructural evolution of commercially pure titanium (CP-Ti) and Ti6Al4V powders manufactured by the Armstrong process deposited by cold spray with nitrogen and helium. The unique, coral-like morphology of the powders resulted in high density deposits sprayed with both nitrogen and helium carrier gasses. The plastic deformation of the CP-Ti and Ti6Al4V particles upon impact leads to refinement of the equiaxed grains present in the starting powder. CP-Ti deposits sprayed with nitrogen result in a grain size of 1 +/- 0.6 mu m while deposit processed with helium results in a grain size of 0.7 +/- 0.2 mu m with no clear difference between the grain size at particle interiors and at prior particles boundaries. The low levels of intragranular misorientation in the CP-Ti helium deposit indicated the presence of recrystallized grains. The higher grain refinement when using helium as carrier gas resulted in a weak basal plane (0001) fiber texture. Regions of ultrafine grains are also identified in the microstructure of Ti6Al4V analyzed by SEM. Microhardness values of the deposits made with these coral-like morphology powders were similar to CP-Ti and Ti6Al4V cold sprayed deposits produced with spherical powders.
查看更多>>摘要：In order to meet the clinical demand for titanium implants, the heterogeneous structure of TiO2/SrTiO3 coating was in situ fabricated on the surface of Ti6Al4V alloy by a facile way. The well-designed Ti6Al4V/TiO2/SrTiO3 composite exhibits a strong photocatalytic antibacterial efficiency against Escherichia coli (E. coli). The suitable energy band structure, improved light absorption and enhanced carrier separation of TiO2/SrTiO3 heterojunction facilitate the generation of bactericidal reactive oxygen species (ROS) under the illumination of UV light. The biocompatible SrTiO3 component effectively favors the adhesion, proliferation and osteogenic differentiation of human bone mesenchymal stromal cells (hBMSCs) in vitro. It is worth noting that the dense oxide coating provides a reliable barrier against tribocorrosion for the titanium alloy substrate, and the wear volume loss of the Ti6Al4V/TiO2/SrTiO3 reduces to 1/8 of that of the bare Ti6Al4V alloy in simulated body fluid. In this work, a multifunctional coating system was proposed to provide inspiration for the development of novel artificial bone implant materials.
查看更多>>摘要：To enhance the adhesion strength and tribological properties of hydrogenated diamond-like carbon (H-DLC) films, the multi-layered H-DLC films consisting of a function layer with chromium and boron doping, Cr-C and Cr-H-DLC transition layer and a Cr bonding layer were prepared on 52100 steel through the unbalanced magnetron sputtering system. The influence of Cr and B doping on the mechanical properties and tribological performance were investigated. The results indicated that the structure of H-DLC, Cr-H-DLC and B-H-DLC films was compact. There were no peelingflake, delamination, and crack between the films and substrate. Raman spectra showed that the value of I-D/I-G increased with the Cr and B doping, which indicated that the sp(3) content inside the H-DLC film decreased. Compared with the atmospheric condition, the coefficient of friction and wear rate of those films were higher than that in vacuum. According to the Raman spectra of the wear track, it was found that the graphitization of sliding interface theory had its limitations. The mechanical wear of those films was dominated by the abrasive and oxidative wear in the atmospheric environment. Owing to the passivation of the hydrogen atoms, the abrasive wear and adhesive wear was the main failure mechanism in vacuum.
查看更多>>摘要：In this study the possibility to employ magnetron-based gas aggregation source for the effective and facile production of mesoporous vanadium films composed of individual vanadium nanoparticles is investigated. It is demonstrated that due to the high deposition rate of V nanoparticles under optimized conditions, their low impact energies, and the directionality of the deposition process, it is possible not only to produce porous nanoparticle coatings, but also coatings with columnar structures. Furthermore, it is shown that such produced coatings may be easily transformed into vanadium pentoxide ones by their annealing in air at the temperature of 550 ?C, without loosening the mesoporous character of resulting films.
查看更多>>摘要：In view of the good thermal insulation, good high-temperature phase stability, high thermal expansion coefficients and ferroelastic transformation of YTaO4 ceramics, which can be prepared as thermal insulation and anti-oxidation coating material on Ti6Al4V alloy (TC4). Herein, a bond coating (BC, NiCrAlY) and top coating (TC, YTaO4) were deposited on a TC4 surface via atmospheric plasma spraying (APS), the microstructure, multi scale mechanical properties and failure mode of TC were investigated. XRD results demonstrate YTaO4 coating has good phase stability below 900 ?, both average particle size and intrinsic strain are calculated by Williamson-Hall (W-H) method. The surface hardness, wear resistance and service life of YTaO4 coating deposited on TC4 is higher than that of pure TC4, and thermal shock tests results (> 300 times at 900 ?; 269 times at 1000 ?; 79 times at 1100 ?) exhibits YTaO4 coating has an excellent protective effect against thermal shock and oxidation for TC4.
查看更多>>摘要：This study aims to investigate friction and wear performance of a novel volcano-shaped textured PVD coating, hoping to find the influence mechanism of volcano-shaped texture on the tribological behavior of textured coated surface. The volcano-shaped texture was fabricated on the sample surface by laser, and then PVD coating was deposited. For samples with different texture diameters or texture area ratios, reciprocating pin-on-disk wear tests were conducted to study tribological properties. After tests, wear topographies of samples and counter pins were observed to analyze wear details. The results showed volcano-shaped texture with suitable diameters and area ratios was conducive to lowering friction coefficient and reducing adhesive wear. The optimal texture diameter and area ratio were 310 mu m and 25%, respectively. Meanwhile, the texture with large area ratios increased friction. These results indicated this texture's potential for friction control. Finally, the influence mechanism of volcano-shaped texture was proposed.
查看更多>>摘要：During plasma spraying, interactions between successive impacting particles/droplets are critical to the interfacial bonding properties between splats and the microstructural development of the bulk coating. The transient spreading process of two successive plasma- sprayed Ni20Cr droplets with different impacting spacing was numerically studied while the interfacial features between these two solidified splats were experimentally characterized by focused ion beam (FIB) microscope and transmission electron microscope (TEM). Droplets directly impacting onto the center of a previously deposited splat solidified quickly, inducing splashed fingers and smaller solidified grains. A higher droplet impact temperature could remelt the bottom splat and promote metallurgical bonding along the splat-splat interface more readily. For droplets impacting away from the previously solidified splat, the second molten droplet could either climb over the periphery of the previous splat inducing significant finger splashing, or spread beneath the curling-up splat modifying the solidification process. The solidification behavior of the subsequent droplet at the splat-splat interaction region played an important role in influencing the formation of inter-splat pores and grain growth.
查看更多>>摘要：Spiral blades are the main working mechanism of shearers, and the service life of blades directly affects the coal-rock cutting progress and enterprise production efficiency. To repair the damaged spiral blade and improve the wear resistance, FeCrSiB coatings having different amounts of reinforcing TiC particles were fabricated on the blade material 34CrNiMo6 by laser additive manufacturing technology. The effects of the TiC particle weight fraction on the microstructure, phase, hardness and wear resistance of the TiC/FeCrSiB composite coating were systematically studied. A laser additive remanufacturing repair experiment of damaged spiral blades based on reverse engineering technology was performed. The results indicated that the composite coating had good metallurgical bonding with the 34CrNiMo6 substrate, and the TiC particles converged towards the top of the coating via Marangoni convection and dynamic viscosity. The composite coatings mainly consisted of gamma-(Fe, Cr) solid solution, M23C6, Fe2B/Cr2B and TiC. By increasing the TiC concentration in the composites, the hardness and wear resistance of the coating were significantly improved. The Rockwell hardness, microhardness and wear rate of the 30%-TiC-reinforced coating were 74.82 HRC, 1143.61 HV0.5 and 0.45 x 10(-2) mm(3)N(-1) mm(-1), respectively, and the wear resistance of the composite coating was 9 times higher than that of the substrate. The experimental results show that the laser additive remanufacturing TiC reinforced coating was an effective method to repair damaged spiral blades and improve the service performance.
NSTL
Elsevier