| 1. |
- Ray, A. K., et al.
(författare)
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Damage resistance of a thermal barrier coated superalloy used in aero turbine blade under accelerated creep condition
- 2009
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Ingår i: High Temperature Materials and Processes. - 0334-6455 .- 2191-0324. ; 28:1-2, s. 35-53
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Tidskriftsartikel (refereegranskat)abstract
- This paper highlights the hot tensile and accelerated creep properties of a thermal barrier coated (TBC) AE 437A alloy used as a candidate blade material in aero engines. Acoustic emission technique has been utilised to characterise the ductile-brittle transition temperature of the bond coat. Results revealed that the DBTT (ductile to brittle transition temperature) of this bond coat is around 923 K, which is in close proximity to the value reported for NiCoCrAlY type of bond coat. Finite element technique used for analysing the equivalent stresses in the bond coat well within the elastic limit, revealed highest order of equivalent stress at 1073 K as the bond coat is ductile above 923 K. The lifetime of the TBC coated superai loy was superior to that of the bare substrate and that oxidation is likely the cause of the reduced life of the bare substrate as compared to the coated substrate while stress rupture or accelerated creep experiments are carried out in an oxidizing environment.. Delamination of the bond coat and that of the TBC at high stresses during accelerated creep was evident. During accelerated creep, the mode of fracture in the substrate at very high stresses was transgranular whereas that at low stresses was intergranular.
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| 2. |
- Kaur, N., et al.
(författare)
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Study of mechanical properties and high temperature oxidation behavior of a novel cold-spray Ni-20Cr coating on boiler steels
- 2015
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Ingår i: Applied Surface Science. - 0169-4332 .- 1873-5584. ; 328, s. 13-25
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Tidskriftsartikel (refereegranskat)abstract
- In the current investigation, high temperature oxidation behavior of a novel cold-spray Ni-20Cr nano-structured coating was studied. The nanocrystalline Ni-20Cr powder was synthesized by the investigators using ball milling, which was deposited on T22 and SA 516 steels by cold spraying. The crystallite size based upon Scherrer's formula for the developed coatings was found to be in nano-range for both the substrates. The accelerated oxidation testing was performed in a laboratory tube furnace at a temperature 900 degrees C under thermal cyclic conditions. Each cycle comprised heating for one hour at 900 degrees C followed by cooling for 20 min in ambient air. The kinetics of oxidation was established using weight change measurements for the bare and the coated steels. The oxidation products were characterized by X-ray Diffraction (XRD), Scanning Electron Microscopy/Energy Dispersive Spectroscopy (SEM/EDS) and X-ray mapping techniques. It was found from the results that the coating was successful in reducing the weight gain of SA213-T22 and SA 516-Grade 70 steel by 71% and 94%, respectively. This may be attributed to relatively denser structure, lower porosity and lower oxide content of the coating. Moreover, the developed nano-structured Ni-20Cr powder coating was found to perform better than its counterpart micron-sized Ni-20Cr powder coating, in terms of offering higher oxidation resistance and hardness. (C) 2014 Elsevier B.V. All rights reserved.
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| 3. |
- Lansford, Jennifer E, et al.
(författare)
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Corporal Punishment, Maternal Warmth, and Child Adjustment : A Longitudinal Study in Eight Countries
- 2014
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Ingår i: Journal of clinical child and adolescent psychology (Print). - : Informa UK Limited. - 1537-4416 .- 1537-4424. ; 43:4, s. 670-685
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Tidskriftsartikel (refereegranskat)abstract
- Two key tasks facing parents across cultures are managing children’s behaviors (and misbehaviors) and conveying love and affection. Previous research has found that corporal punishment generally is related to worse child adjustment, whereas parental warmth is related to better child adjustment. This study examined whether the association between corporal punishment and child adjustment problems (anxiety and aggression) is moderated by maternal warmth in a diverse set of countries that vary in a number of sociodemographic and psychological ways. Interviews were conducted with 7- to 10-year-old children (N = 1,196; 51% girls) and their mothers in 8 countries: China, Colombia, Italy, Jordan, Kenya, the Philippines, Thailand, and the United States. Follow-up interviews were conducted 1 and 2 years later. Corporal punishment was related to increases, and maternal warmth was related to decreases, in children’s anxiety and aggression over time; however, these associations varied somewhat across groups. Maternal warmth moderated the effect of corporal punishment in some countries, with increases in anxiety over time for children whose mothers were high in both warmth and corporal punishment. The findings illustrate the overall association between corporal punishment and child anxiety and aggression as well as patterns specific to particular countries. Results suggest that clinicians across countries should advise parents against using corporal punishment, even in the context of parent-child relationships that are otherwise warm, and should assist parents in finding other ways to manage children’s behaviors. © 2014 Copyright Taylor & Francis Group, LLC.
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