Wear and corrosion of metal-matrix (stainless steel or NiTi)-TiC coatings

AbstractDifferent spraying technologies (plasma and High Velocity Oxi-Fuel) have been use to obtain TiC - stainless steel or NiTi matrix coatings. The starting feedstock powders have been obtained by SHS technology. After crushing and sieving, the fraction of particles between 20 and 63μm, have been selected for thermal spray. The obtained coatings have been characterized by XRD and SEM-EDS to observe the surface and cross section. The coatings adhesion, wear (ball-on-disk and rubber wheel tests) and electrochemical corrosion test have been carried out.Results show that the plasma sprayed coatings with NiTi have better adhesion than the stainless steel matrix coatings. However, the opposite happens for HVOF coatings. NiTi matrix coatings exhibit higher wear resistance both for plasma and HVOF spraying processes

Estudio sobre los coronavirus más relevantes en animales domésticos y su relación con coronavirus humanos

El SARS-CoV-2 (del inglés severe acute respiratory syndrome coronavirus 2) es un nuevo coronavirus identificado por primera vez en la ciudad china de Wuhan a finales de 2019. Este virus ha sido responsable de la COVID-19 (del inglés Coronavirus Disease), una enfermedad que rápidamente se fue extendiendo por todo el planeta y ha puesto el foco de atención de la comunidad científica y el público en general en este grupo de virus y los mecanismos que justifican su origen para causar una pandemia sin precedentes en las últimas décadas. El origen del SARS-CoV-2 se relacionó tempranamente con coronavirus de murciélagos y su posible paso a través de mamíferos como el pangolín (Mammalia, Pholidota) hasta alcanzar la especie humana. No obstante, los coronavirus son patógenos ampliamente reconocidos por los veterinarios como causantes de diversas enfermedades en los animales. En este trabajo de fin de grado se revisan algunos de los coronavirus más importantes en veterinaria y en el hombre, con especial referencia al SARS-CoV-2, incluyendo aspectos de su biología, patología y control, así como las relaciones filogenéticas entre estos coronavirus animales y los humanos.Los resultados del trabajo revelan la gran diversidad de los coronavirus, con 52 especies actualmente reconocidas, entre las cuales destacan algunas causantes de enfermedades de gran interés médico y económico, como la peritonitis infecciosa felina, gastroenteritis transmisible porcina, diarrea epidémica porcina, diarrea neonatal de los terneros o bronquitis infecciosa aviar. En humanos son siete las especies de coronavirus reconocidas hasta el momento, algunas implicadas en la etiología de cuadros catarrales, aunque tres especies del género Betacoronavirus (SARS-CoV, MERS-CoV y SARS-CoV-2) han sido responsables de epidemias con síndromes respiratorios graves, destacando esta última como causante de la pandemia de COVID-19. Los resultados confirman la importancia de los murciélagos como reservorios de coronavirus, al ser hospedadores de 13 especies, muchas de las cuales se consideran ancestros de coronavirus que infectan a mamíferos y aves, entre las cuales se incluye el SARS-CoV-2. El acúmulo de mutaciones o la recombinación genética se consideran clave en la emergencia de nuevos coronavirus, aunque su salto a la especie humana requiere normalmente el paso por diversos hospedadores intermediarios, circunstancia que se ve favorecida por factores como la globalización y un contacto estrecho del hombre con diversos animales domésticos y silvestres. No se ha podido confirmar cual es el hospedador intermediario a través del cual se ha producido el salto del SARS-CoV-2 al ser humano, aunque el perro mapache (Nyctereutes procyonoides) se considera entre los más probables. Asimismo, se constata que los coronavirus de mamíferos y aves domésticas no han tenido protagonismo en el origen del SARS-CoV-2, del cual están filogenéticamente distantes, aunque son receptivos a la infección por el virus desde el ser humano, lo que confirma la COVID-19 como zoonosis inversa.<br /

Wear resistance of nanostructured Cr-based WC hardmetals sintered by spark plasma sintering

Erratum to 'Wear resistance of nanostructured Cr-based WC hardmetals sintered by spark plasma sintering' [International Journal of Refractory Metals and Hard Materials Volume 87, February 2020, 105121]. DOI: https://doi.org/10.1016/j.ijrmhm.2020.105206Nanostructured Cr-based WC hardmetals are successfully sintered by spark plasma sintering. The wear behaviour of these Cr-based WC hardmetals with different C contents ranging from 5.57 wt% to 6.91 wt%, is evaluated performing sliding wear tests under two different wear conditions. This work analyses the influence of the C content on the wear performance through the study of the phase formation and WC grain size. The Cr-based hardmetal with 5.57 wt% C content exhibits a lower wear rate than Co-based WC hardmetals tested under similar dry ball-on-plate wear conditions, even considering that these Co-based WC hardmetals have higher WC content (90 wt%) than Cr-based WC hardmetals (83.2 wt%). The combination of a nanosized WC grain and the avoidance of brittle (Cr,Fe)7C3 or soft graphite phases leads to a superior wear performance. Thus, the use of Cr-based binders in the hardmetal industry, alternatively to Co-based binders, is promising in applications in which high wear resistance is needed

Effect of MRI on preterm infants and their families: a randomised trial with nested diagnostic and economic evaluation.

BACKGROUND: We tested the hypothesis that routine MRI would improve the care and well-being of preterm infants and their families. DESIGN: Parallel-group randomised trial (1.1 allocation; intention-to-treat) with nested diagnostic and cost evaluations (EudraCT 2009-011602-42). SETTING: Participants from 14 London hospitals, imaged at a single centre. PATIENTS: 511 infants born before 33 weeks gestation underwent both MRI and ultrasound around term. 255 were randomly allocated (siblings together) to receive only MRI results and 255 only ultrasound from a paediatrician unaware of unallocated results; one withdrew before allocation. MAIN OUTCOME MEASURES: Maternal anxiety, measured by the State-Trait Anxiety inventory (STAI) assessed in 206/214 mothers receiving MRI and 217/220 receiving ultrasound. Secondary outcomes included: prediction of neurodevelopment, health-related costs and quality of life. RESULTS: After MRI, STAI fell from 36.81 (95% CI 35.18 to 38.44) to 32.77 (95% CI 31.54 to 34.01), 31.87 (95% CI 30.63 to 33.12) and 31.82 (95% CI 30.65 to 33.00) at 14 days, 12 and 20 months, respectively. STAI fell less after ultrasound: from 37.59 (95% CI 36.00 to 39.18) to 33.97 (95% CI 32.78 to 35.17), 33.43 (95% CI 32.22 to 34.63) and 33.63 (95% CI 32.49 to 34.77), p=0.02. There were no differences in health-related quality of life. MRI predicted moderate or severe functional motor impairment at 20 months slightly better than ultrasound (area under the receiver operator characteristic curve (CI) 0.74; 0.66 to 0.83 vs 0.64; 0.56 to 0.72, p=0.01) but cost £315 (CI £295-£336) more per infant. CONCLUSIONS: MRI increased costs and provided only modest benefits. TRIAL REGISTRATION: ClinicalTrials.gov NCT01049594 https://clinicaltrials.gov/ct2/show/NCT01049594.EudraCT: EudraCT: 2009-011602-42 (https://www.clinicaltrialsregister.eu/)

Microstructural effects of strain aging on NiTi pseudoelastic wires by synchrotron X-ray micro-diffraction

In this work, we explore the consequences of strain aging pseudoelastic NiTi wires (2.46 mm diameter) at moderate temperatures (100ºC). The changes of the stress-strain behaviour on aged, as compared with non-aged wires, with comparatively smaller changes in thermal transformation, indicate the existence of relevant strain fields on these wires. The fact that thinner wires perform differently on aging suggests the possibility of radial dependence of the strain fields. Measurements were performed at CELLS-ALBA synchrotron, BL04 Materials Science Powder Diffraction beam-line. X-ray micro-diffraction for near 10 (μm)2 (FWHM) zones on cross-sections of samples was done, aiming to detect residual strains as function of radial position on the wire. The results show very small changes of diffraction peaks position, with more relevant variations near the surface. This might be interpreted as a high sensitivity of the transformation on stresses enabling defined paths of transformation.

NiTi splat features during vacuum thermal spraying onto several substrates

Postprint (author’s final draft

Analysis of iron aluminide coated beams under creep conditions in high-temperature four-point bending tests

Recent research is focused on the possibility to coat a metallic alloy with intermetallics or ceramics to improve wear and corrosion resistance, as well as creep behaviour at high temperatures, next to other properties of the alloy. Nowadays, this gains importance due to stricter environment guidelines. Here, we present a model to describe a non-symmetric compound in a high-temperature four-point bending test, performed at 400°C. The substrate material is an aluminium alloy AlSi10MgT6, and the coating material is the iron aluminide Fe24Al0.6Nb. Up next, a layer-wise theory is introduced to calculate the forces between substrate and coating. Furthermore, required material parameters are identified, and a new procedure to determine Young’s modulus of a coating is presented. Finally, simulation results are compared to experimental data, illustrating that the presented model is able to describe the material behaviour accurately

Mechanical and nanoindentation behavior of NiTi and NiTi-TiC coatings obtained by thermal spray

Postprint (published version