Polycystic Ovary Syndrome (PCOS) is associated with a chronic low-grade inflammation and predisposition to hemostatic and atherosclerotic complications. This case-control study evaluated the ...microparticles (MPs) profile in patients with the PCOS and related these MPs to clinical and biochemical parameters. MPs derived from platelets (PMPs), leuckocytes (LMPs) and endothelial cells (EMPs) were evaluated, as well as MPs expressing tissue factor (TFMPs), by flow cytometry, comparing women with PCOS (n = 50) and a healthy control group (n = 50). PCOS women presented increased total MPs, PMPs, LMPs and EMPs levels when compared to control group (all p < 0.05). TFMPs was similar between the groups (p = 0.379). In conclusion, these MPs populations could be useful biomarkers for association with thrombosis and cardiovascular disease in PCOS women.
•PCOS women present increased total microparticles (MPs).•MPs derived from platelets and leuckocytes are increased in PCOS group.•PCOS women present higher MPs derived from endothelial cells.
The corrosion susceptibility of borided CoCrMo alloy exposed to a diffusion annealing process (DAP) and immersed during 7 days in a Hank's solution was evaluated, being compared with the results ...obtained in the borided CoCrMo alloy and the CoCrMo alloy. Firstly, the CoCrMo alloy was exposed to the powder-pack boriding process during 5 h at 1273 K, to obtain a biphasic layer (CoB-Co2B) with a total thickness around 33 μm. Then, the DAP was performed on the borided CoCrMo alloy during 2 h at 1273 K in an inert argon atmosphere to obtain a 29 μm of monophasic Co2B layer. The corrosion tests were performed by the potentiodynamic polarization technique to estimate the corrosion resistance (Rp) and the corrosion current density (jcorr) by means of the linear polarization and the Tafel extrapolation techniques, respectively. The results showed, in the 7th day of immersion in the Hank's solution, that the borided CoCrMo alloy exposed to the DAP exhibited a corrosion value ~22 times higher (~357 kΩ cm2) than that obtained in the borided CoCrMo alloy (~15 kΩ cm2), reaching a value close to the CoCrMo alloy (~385 kΩ cm2). The corrosion performance of the borided CoCrMo alloy exposed to the diffusion annealing process was attributed to i) the presence of the monophasic Co2B layer and high contents of Cr and Mo on the outer-zone of the borided surface, and ii) the depletion of the B2S3 and CrPO4 species at the surface of the borided CoCrMo alloy. Finally, the borided CoCrMo alloy exposed to the DAP exhibited a corrosion susceptibility around 7%, meanwhile the borided CoCrMo alloy obtained a value of 96%, approximately.
•The corrosion resistance of the cobalt boride layer was improved by the DAP.•The DAP increased the Cr and Mo contents on the outermost zone of the Co2B layer.•Depletion of B2S3 and CrPO4 was observed in the boride layer exposed to the DAP.•The boride layer exposed to the DAP showed a corrosion susceptibility of ~7%.
The kinetics of the FeB/Fe2B layers and diffusion zone at the surface of AISI 316 steels exposed to the powder-pack boriding process were studied in this work. FeB/Fe2B layers and diffusion zone ...measurements were taken at different temperatures and exposure times to validate diffusion-controlled growth during the boriding process. In order to obtain the boron diffusion coefficients at the FeB/Fe2B layers and diffusion zone, a mathematical model based on the mass balance at the growing interfaces was proposed. The activation energy values estimated for the FeB and Fe2B layers were 204 and 198kJmola degree 1 respectively. In addition, the activation energy value obtained for the diffusion zone was 116kJmola degree 1. The diffusion model was extended to estimate the FeB/Fe2B layer thicknesses, and the depth of the diffusion zone at the temperature of 1243K with 3 and 5h of exposure, based on the experimental parameters ascribed to the boriding process. Finally, the effects of the FeB/Fe2B growth and diffusion zone, on the weight gain of borided steels and on the instantaneous velocity of the interfaces were incorporated in the model.
In this study the mechanical behavior of FeB and Fe2B layers formed at the surface of AISI D2 steels was estimated by the Berkovich nanoindentation technique. The boriding of AISI D2 steels was ...developed by the powder-pack method at temperatures of 1223, 1273 and 1323K with exposure times of 3–7h for each temperature. The mechanical characterization was performed to determine the effect of the set of experimental parameters of the boriding process with three experimental procedures: first, nanoindentation was performed along the depth of the surface layers at a constant load of 250mN to determine the hardness gradient and the state of the thermal residual stresses in the boride layers; then, loads in the range of 10 to 300mN were applied to the “pure” zone of the FeB layer at a distance of 10μm from the surface, and in the “pure” zone of the Fe2B layer (40μm), respectively. Finally, the fracture toughness, compressive residual stresses, and brittleness of the boride layers were evaluated using the length of the cracks that originated from the corners of the Berkovich nanoindentation site after the application of loads ranging from 300 to 500mN.
For a constant load of 250mN, the results showed that the state of thermal residual stresses and the hardness of both the FeB and Fe2B layers were a function of the temperature and exposure time of the process. Moreover, the presence of the indentation size effect (ISE) in the FeB and Fe2B layers was verified in the range of applied loads (10–300mN), in which the apparent or real hardness was estimated by the elastic recovery (ER) model according to the boriding experimental parameters. Finally, the estimated values of the fracture resistance and brittleness of the boride layers fell within the range of 1.48–3.02MPam and 2.01–4.65MPam, with the presence of compressive stresses in the range of 428 to 1604MPa for the FeB and Fe2B layers, respectively.
► Mechanical properties of the FeB and Fe2B layers were evaluated by nanoindentation. ► The thermal residual stresses across the boride layers were compressive. ► The presence of the indentation size effect was verified in both FeB and Fe2B layers. ► The FeB layer showed low fracture resistance with high brittleness.
New results about the scratch adhesion resistance of nickel boride layer on Inconel 718 superalloy were estimated in the present study. The nickel boride layer was developed on the surface of Inconel ...718 superalloy by means of the powder-pack boriding process conducted at 1173K with 2, 4, and 6h of exposure. The microstructure of the nickel boride layer was analyzed from optical microscopy, X-ray diffraction and energy dispersive spectroscopy (EDS). Furthermore, and before the scratch tests, indentation properties of the nickel boride layers such as hardness, Young's modulus, and the distribution of residual stresses were evaluated using Berkovich nanoidentation tests applying a constant load (50mN) across the diffusion layers. The scratch tests were performed over the surface of the nickel boride layer-substrate systems using a Rockwell-C diamond indenter with a continuously increasing normal force from 1 to 80N, whereas the behavior of the coefficient of friction and the residual depth as a function of the scratch length were monitored during the tests. For the determination of the critical loads, the combination of acoustic emission signal with microscopic observations of the worn tracks were used; the critical loads were estimated at which the layer cracks (cohesive failure) or is detached (adhesive failure) and they explained according to the mechanical properties of the nickel boride layer-substrate system. For all the set of experimental conditions, the presence of three types of failure mechanisms over the worn tracks were detected, while the results showed that the critical loads increase with enhancing nickel boride layer thickness.
•New results about the adhesion resistance of nickel boride layer were obtained.•From scratch test, the critical loads of the layer-substrate system were estimated.•Tensile residual stresses decrease the practical adhesion resistance of the layer.•The adhesion resistance increases as a function of the boride layer thickness.•Hertzian cracking, chipping and spalling were observed over the scratch tracks.
New data for micro-abrasion wear resistance of CoB/Co2B coating was obtained through a ball cratering test. The coating was formed on the surface of a CoCrMo alloy using the powder-pack boriding ...method. The boriding process was carried out at 1223K over 5h of treatment resulting in the formation of CoB/Co2B coating with a total thickness of 28μm approximately. Both hardness and Young's modulus profile through the cobalt borides were evaluated by Berkovich depth-sensing indentation using a load of 25mN. The wear coefficients of CoB and Co2B formed on CoCrMo alloy were evaluated by a Plint TE-66 micro-abrasion tester using SiC particles dissolved in deionized water as abrasive slurry. The results demonstrated that the cobalt borides have wear coefficients higher than CoCrMo and improve their micro-abrasion wear resistance. Furthermore, a wear-mode map was developed to identify the two and three body abrasion mechanisms and the transition between them modifying the concentration of SiC in the slurry and the magnitude of applied load.
•New wear resistance data for cobalt borides were estimated by micro-abrasion tests.•The wear coefficients were determined for CoB and Co2B phases.•The wear-mode map was obtained for CoB phase.•The two-body, three-body, and mix mode wear mechanism were identified in CoB phase.
New results about the influence of a small iron borided layer (~ 36
µ
m) obtained by the powder-pack boriding process (PPBP) and diffusion annealing post-process (DAP) were evaluated. Dry sliding ...wear tests on PPBP, PPBP + DAP and untreated AISI 1018 steel were performed under the pin-on-disc configuration, and balls of Al
2
O
3
and WC were used as a counterpart at different sliding distances. Also, the contact pressures of the layer/substrate system were evaluated using the finite element model with the aid of the ABAQUS software. The results showed that the Al
2
O
3
ball presented the major coupling (ball-disc), and the PPBP + DAP reduces the specific wear rate around ~ 304 times related to the untreated AISI 1018 steel to 500 m under severe sliding conditions.
Graphical Abstract
•Boriding reduced friction by up to 30% compared to heat-treatment in dry tests.•In dry tests, the borided steel showed mild wear and the heat-treated steel showed severe wear.•Grease lubrication ...reduced friction similarly in the borided and heat-treated steel.•The wear resistance of the borided steel improved by about 10 times using grease.
This work presents new results about the dry and grease-lubricated wear resistance of borided AISI 52100 steel. Boriding was conducted at 850 °C for 1 h. The reciprocating wear tests were conducted with an alumina ball of 6 mm of diameter, with normal load of 20 N and sliding distances of 100, 150 and 200 m; a lithium grease was employed for lubrication. In comparison with heat-treated AISI 52100 steel, boriding reduced the coefficient of friction by 15–30% in dry conditions, although both stabilized similarly in grease-lubricated tests. In addition, the results showed that, for the longer sliding distance, boriding increased the wear resistance up to 8 times in dry conditions and up to 10 times using grease for lubrication. The implementation of boriding significantly improved the tribological performance of AISI 52100 steel in both tests conditions.
The boriding process is a branch of materials heating treatments that studies the improvement of the mechanical properties in steels and alloys. Recently, the borided trends have been studied by a ...selected group of researchers around the world with an interest to divulge the new results on borided materials for different industrial and biomedical applications. The aim of this study is to provide an overview of the historical review of the boriding process using the Bibliometric analysis. In total, 1227 documents in the Scopus database have used the boriding process as keyword with a growth rate of 7.3% every year from 1962 to 2020. The papers were written by around 2434 authors, mainly from Mexico, Turkey, and Poland, representing 37.7% of the total publications analyzed. The data obtained show that the boriding process has been global and fast-growing in the scientific publications of the last ten years.
Graphic Abstract
In this study, new data about the growth kinetics and indentation properties of cobalt boride layers formed on the surface of the ASTM F-75 biomedical alloy were estimated. The boron diffusion at the ...surface of the biomedical alloy was conducted using a powder-pack boriding process at temperatures of 1223–1273K with different exposure times for each temperature. Two mathematical approaches were proposed to determine the boron diffusion coefficients of the CoB and Co2B layers in the range of boriding temperatures, in which the experimental results of the kinetics of the cobalt boride layers were compared with those estimated using diffusion models.
Finally, the mechanical characterization of the cobalt boride layers was evaluated by indentation techniques with applied loads of 0.98N and 50mN, respectively. According to the nanoindentation tests, a maximum hardness value (30GPa) and a maximum Young's modulus (380GPa) were obtained near the surface region (5μm) of the borided cobalt alloy.
•New data about the growth kinetics of cobalt boride layers were estimated.•The diffusion models can be adopted to determine the thickness of the boride layer.•Indentation properties were evaluated along the depth of the CoB and Co2B layers.•Vacuum aging should be the preferred aging method for most of the beef industry.•Vacuum aging should be the preferred aging method for most of the beef industry.
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