The CoCrMo alloy is a biomaterial that has been employed for the production of permanent orthopedic implants, however, the release of metallic ions from debris due to tribocorrosion is the main ...drawback for its extended application. In this paper, we propose the use of the ball burnishing process to improve the surface properties of the CoCrMo alloy. A 32 factorial design of experiments (DoE) was conducted to achieve a basic understanding of the relationship between the surface hardness, roughness and corrosion current (response variables) and the force and number of passes of the burnishing tool (input factors). Statistical analysis showed that force is the most significant factor for changing the surface properties. At the best experimental conditions, hardness was improved by 41.4%, the roughness was decreased by 72.7% and the corrosion rate was noticeably reduced by 92.4%. Microscopy and X-ray diffraction analysis showed that ball burnishing introduces changes in the microstructure, generating a surface layer with improved properties. It is concluded that the ball burnishing process is suitable for improving the surface properties of the CoCrMo alloy under an appropriate combination of experimental conditions.
Living with degenerative diseases, such as arthritis and osteoporosis, is challenging if orthopedic devices manifest adverse effects caused by corrosion processes. Ti6Al4V alloy is used to ...manufacture orthopedic implants due to its excellent mechanical and osseointegration properties. Nonetheless, it has poor resistance to wear and corrosion by biological fluids and mechanical activity. This degradation process generates the need to improve the corrosion resistance of metallic biomaterials used as biomedical implants. Dip-coating technique is a wet coating method used to lessen wear damage on the metal surface and can produce coatings using a wide variety of molecules at a low cost. In this work, Ti6Al4V alloys were coated with ultra-high molecular weight polyethylene (UHMWPE) and Octadecylphosphonic Acid (ODPA) films forming a UHMWPE/ODPA bilayer coating by dip-coating method to improve protection efficiency against corrosion in phosphate-buffered isotonic saline solutions and proposed it as alternative coatings to delay the failure of medical implants. The optimization of individual coated systems were obtained with an immersion time of 40 s (Ti6Al4V/UHMWPE) and 30 h (Ti6Al4V/ODPA) with corrosion current densities of 1.51 × 10−9 A cm−2 and 6.8 × 10−8 A cm−2, respectively. The formation of bilayer coatings reduces the average roughness from 19.34 nm (Ti6Al4V/UHMWPE) to 12.67 nm (Ti6Al4V/UHMWPE/ODPA). ODPA deposition on UHMWPE films changes the corrosion rate by interfering with the anodic and cathodic reactions, reducing the corrosion rate to 7.46 × 10−4 μm y−1 and an estimated corrosion protection efficiency of about 99.99 %. The results show a superior performance as a protective barrier over the individual films (1.19 μm y−1 with 97.2 %, and 0.026 μm y−1 with 99.9 %, ODPA, and UHMWPE, respectively), improving the corrosion resistance of the Ti6Al4V alloys.
•ODPA inhibits the corrosion process on Ti6Al4V substrates.•Consistent morphology, sealing pores, was observed in bilayered UHMWPE/ODPA films.•ODPA films seal effectively the common pores formed in Ti6Al4V/UHWPE coatings.•ODPA films enhance corrosion resistance of Ti6Al4V/UHWPE systems using a PBS solution.•ODPA thin film is a promissory coating to be used in biomedical applications.
Structural evolution during the synthesis of B2–NiAl intermetallic compound by mechanical alloying of equiatomic elemental mixtures was studied by Rietveld analysis, DSC and HTXRD. The lattice ...parameter, crystallite size, microstrain, amount of phase and ordering of the B2 phase were monitored as a function of milling time. Formation of the B2–NiAl phase shows a sigmoidal behavior, which suggests that Johnson–Mehl–Avrami nucleation and interface-controlled growth are the responsible mechanisms in the transformation. Almost complete transformation (~ 97 mol%) was obtained after 25 h of milling. A specific phase transformation sequence during milling was not absolutely determined, however, the sequence Ni + Al → NiAl
3
→ Ni
2
Al
3
→ B2–NiAl was identified by HTXRD. This sequence was confirmed by DSC. The transformation temperature of the B2–NiAl phase and the presence of additional intermetallic compounds show a direct dependence on the Ni–Al layer spacing. Using a production-scale Simoloyer horizontal Attritor Mill, the presence of Ni
2
Al
3
phase was observed prior to the full synthesis of B2-NiAl.
Y
2
O
3
: Eu
3+
,Tb
3+
transparent, high density and optical quality thin films were prepared by the sol–gel dip-coating technique. Yttrium (III) 2,4-pentadionate was used as a precursor by its ...hydrolysis in ethanol. The doping agents were incorporated in the form of europium and terbium nitrate. Structural, morphological and optical properties of prepared films were investigated for different annealing temperatures in order to establish the ideal processing route that enhances the luminescent properties. X-ray diffraction (XRD) analysis shows the cubic phase for 10-layer films and annealing temperatures higher than 500°C. At 700°C, highly densified (4.52 g cm
−3
) and very smooth films (1.4 nm at 700°C) are produced, composed of crystallites with a grain size of 11 nm. The film thickness, refractive index and porosity, as well as the luminescent properties, were found to vary with treatment temperature.
Europium actived Lu
2
O
3
sol–gel transparent and crack free films were deposited by dipping on silica substrates. The film microstructure was studied by waveguide Raman spectroscopy (WRS) with ...annealing temperatures from 400 up to 1,000 °C and X-ray diffraction. The WRS results and TEM observations were correlated and showed that crystallization of the lutetium oxide phase into cubic phase occurs at 600 °C and is stable up to 1,000 °C, the crystallite size increasing between ±38 nm with annealing temperature ranging from 600 to 1,000 °C. Opto-geometrical parameters were determined by m-lines spectroscopy using four different wavelengths of laser sources in order to confirm the step-index profile of the as-prepared waveguides. The Eu
3+
doped films heat-treated at 1,000 °C presented a constant thickness for the wavelengths 493, 543, 594 and 632.8 nm and a density of 8.4 g cm
−3
. High-resolution X-ray images were obtained.
A study of titanium nitride (TiN) films microstructural and mechanical properties at nanoscale using resonance tracking acoustic force atomic microscopy is presented. Also for this study, the work ...function (Φ
e
) measured for Kelvin Probe Force Microscopy of TiN films deposited by pulsed dc magnetron sputtering is analysed. The films were deposited on Si and glass substrates using a gas mixture ratio Ar-N
2
10 and 12% of N
2
and power density from 7.4 to 10.8 W cm
−2
using the Pulsed DC Magnetron Sputtering. Mechanical properties at nanoscale are measured and a relation between microstructure and nanoscale elastic domains is seen. It was found that the hardness increases when the Φ
e
increases. This directly proportional relationship between hardness and work function, for the first time observed and reported in this contribution, is more accurate and shows a stronger dependence than the relation between hardness and microstructural properties independently.
The ASTM A-36 steel is the main alloy, used in the metal-mechanical industry. In the present study, the effect of boron-carbon coating on the hardness and corrosion resistance of the steel ASTM A-36 ...was reported. Boronizing thermochemical treatment was carried out at 950 °C for 4 h followed by the carburizing process at 930 °C for 6 h. The corrosion study was conducted using the polarization technique (Tafel) and electrochemical impedance spectroscopy (EIS), which employed a fused deposition modeling-based 3D printing electrochemical cell made of polylactic acid (PLA). A commercial platinum foil and an Ag/AgCl (3.5 M KCl) electrode were used as the counter and reference electrode, respectively. The working electrode used an area of 1 cm2 of the sample. Optical microscopic analysis shown that borides formed on the surface of steels has a saw-tooth morphology and a uniform coating with a thickness of about 60 µm in both samples. The carburizing over boride promoted the formation of coatings on the outermost layer of the samples with a thickness of about 17 µm over the boride layer. Boride formation was verified by X-ray diffraction (XRD) analysis indicating only the formation of the Fe2B phase. Results showed that boride samples exhibited inferior corrosion resistance compared to original samples, but after carburizing, an outer layer was formed, with the hardness and corrosion resistance like that of the original sample.
This study investigates the corrosion potential of ASTM A-36 steel after slide burnishing using different applied forces. Turned samples of ASTM A-36 steel were subjected to slide burnishing surface ...treatment. The burnishing process was carried out with forces of 150 N, 300 N, and 450 N, at a travel speed of 100 mm/min. The effects of burnishing on the chemical composition of the material were analyzed using Grazing Incidence X-ray Diffraction and X-ray photoelectron spectroscopy, which indicated no changes in the chemical composition of the material. Corrosion potential measurements were performed using the Tafel test. The results showed that as the burnishing force increased, the corrosion potential shifted to lower values. Additionally, roughness analysis suggested that the change in corrosion potential was attributed to plastic deformation caused by the burnishing process. The increased mechanical work exerted on the material during burnishing may be the underlying reason for the observed shift towards lower corrosion potentials with higher applied forces.
La cinética de engrosamiento y la evolución morfológica de precipitados coherentes β’ (Fe, Ni)Al en una matriz ferrítica se estudió en la aleación Fe-10 % Ni-15 % Al. Se solubilizaron muestras a ...1.100 °C por 24, y posteriormente, se envejecieron a 750, 850 y 920 °C por diferentes tiempos. Los resultados de DRX, MEB y MET mostraron la descomposición, αsss → α + β, durante su envejecido. La distribución de precipitados dentro del grano cambia, gradualmente, de aleatoria a un alineamiento preferencial sobre las direcciones cristalográficas de la matriz. Asimismo, la evolución morfológica de los precipitados fue: esféricos → cúbicos → paralelepípedos → placas. La variación del tamaño de partícula, r3, y la densidad de precipitados en función del tiempo se comportan linealmente, como lo predice la teoría de Lifshitz, Slyosov y Wagner (LSW) para el engrosamiento controlado por difusión. La cinética de crecimiento (K) se incrementó a temperaturas de envejecido mayores. La energía de activación para el proceso de engrosamiento fue de alrededor de 220 kJ/mol.
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