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Harpreet Singh Grewal

Bio: Harpreet Singh Grewal is an academic researcher from Shiv Nadar University. The author has contributed to research in topics: Friction stir processing & Corrosion. The author has an hindex of 22, co-authored 89 publications receiving 1281 citations. Previous affiliations of Harpreet Singh Grewal include Korea Institute of Science and Technology & Indian Institute of Technology Ropar.


Papers
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Journal ArticleDOI
TL;DR: Enhanced erosion resistance of HEA was attributed to its high work-hardening behavior and stable passivation film on the surface and no evidence of intergranular corrosion likely due to the absence of secondary precipitates.

134 citations

Journal ArticleDOI
TL;DR: In this paper, the effect of alumina content on the microstructure and various mechanical properties viz. microhardness, fracture toughness, density, residual stress and scratch resistance was studied.
Abstract: In the current work, Ni–Al 2 O 3 based composite coatings were fabricated using High Velocity Flame Spray (HVFS) system. The effect of alumina content on the microstructure and various mechanical properties viz. microhardness, fracture toughness, density, residual stress and scratch resistance was studied. Microstructure of the coating was characterized with the help of Scanning Electron Microscope (SEM) equipped with Energy Dispersive Spectroscopy (EDS), Optical Microscope (OM) and X-ray Diffraction (XRD). It was observed that microstructural properties such as splat size, porosity, un-melted particles and surface roughness are highly affected by the alumina content in the coatings. Microhardness improved with the rise in alumina fraction and a maximum of 1151 HV could be achieved with 60 wt.% alumina blending. Cracking and spallation were found to be the mechanisms responsible for damage of coatings during scratch testing. A model has been proposed to explain the variation in surface roughness and porosity of the Ni–Al 2 O 3 coatings based on coating build-up mechanism.

91 citations

Journal ArticleDOI
TL;DR: In this article, the effect of some of these operating parameters on erosion mechanism of generally used hydroturbine steel, CA6NM (13Cr4Ni), is reported.
Abstract: Performance of hydropower plant is severely affected by the presence of sand particles in river water. Degree of degradation significantly depends on the level of operating parameters (velocity, impingement angle, concentration, particle size and shape), which is further related to erosion mechanism. In this investigation, the effect of some of these operating parameters on erosion mechanism of generally used hydroturbine steel, CA6NM (13Cr4Ni), is reported. Morphology and variation in the martensite and austenite phases of the eroded surfaces were investigated using SEM and XRD. It was observed that velocity and impingement angle affect the erosion mechanism of CA6NM steel. Erosion mechanism was also significantly affected by the radial distance from the impact zone. Primary mechanism responsible for the removal of material at normal impingement angle was the formation and removal of platelets. At acute impingement angle, ploughing was observed to be one of the prime mechanisms responsible for the loss of the material. Other than these two well-known erosion mechanisms, the presence of another two erosion mechanisms was also observed. Models have been proposed for these unfamiliar erosion mechanisms. Interaction amongst different operating parameters was studied using line and contour plots. It was observed that the interaction between velocity and concentration was most significant. Using the experimental results, a statistical model based on regression approach was developed. Validity of this statistical model was checked using the experimental results from the literature and present study.

80 citations

Journal ArticleDOI
TL;DR: In this article, a study of a commonly employed hydroturbine steel, 13Cr4Ni, was conducted using optical microscopy, scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS), X-ray diffraction and electron back scatter diffraction (EBSD) techniques.

75 citations

Journal ArticleDOI
TL;DR: In this paper, WC-Co-Cr coatings were applied on some hydroturbine 13Cr4Ni and 16Cr5Ni steels by the detonation-gun spray process and an in-depth characterization of the as-sprayed coating was done using X-ray diffraction (XRD) and scanning electron microscopy (SEM)/energy-dispersive (EDS) techniques.
Abstract: WC-Co-Cr coatings were deposited on some hydroturbine 13Cr4Ni and 16Cr5Ni steels by the detonation-gun spray process. An in-depth characterization of the as-sprayed coating was done using X-ray diffraction (XRD) and scanning electron microscopy (SEM)/energy-dispersive X-ray spectroscopy (EDS) techniques. Microhardness and porosity measurements were also made. The coating was found to have a typical splat-like morphology with some indications of unmelted carbide particles. The XRD results showed the presence of WC as the primary phase along with W2C and Co6W6C as secondary phases. Furthermore, the slurry erosion behavior of the coatings was investigated to ascertain the usefulness of the coatings to reduce the slurry erosion of the steels. The effect of four operating factors viz. the velocity, impact angle, concentration, and particle size on the slurry erosion of coated and bare steels has been studied using a high-speed jet-type test rig. The sand used as an erodent was collected from a power plant to replicate the actual turbine conditions. It has been observed that the given cermet coating can enhance the erosion resistance of the steel. Velocity was found to be the most significant factor affecting the erosion behavior of the coating, whereas it was the erodent particle size in the case of uncoated steel. As evidenced from the SEM images, the platelet mechanism of erosion seemed to be the prominent one, causing the removal of material from the surface of the steel, whereas for the coating, the formation and interlinking of cracks resulted in the removal of material.

72 citations


Cited by
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[...]

08 Dec 2001-BMJ
TL;DR: There is, I think, something ethereal about i —the square root of minus one, which seems an odd beast at that time—an intruder hovering on the edge of reality.
Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

33,785 citations

28 Jul 2005
TL;DR: PfPMP1)与感染红细胞、树突状组胞以及胎盘的单个或多个受体作用,在黏附及免疫逃避中起关键的作�ly.
Abstract: 抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1(PfPMP1)与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用,在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员,通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

18,940 citations

Journal ArticleDOI
TL;DR: A comprehensive review of surface composites via friction stir processing is presented in this article, where the underlying mechanisms in strengthening of FSP-processed surface composite are discussed with reported models.

408 citations

Journal ArticleDOI
TL;DR: The passive film formed on the equiatomic CoCrFeMnNi high-entropy alloy (HEA) is enriched in Fe and Mn but depleted in Cr.

405 citations

Journal ArticleDOI
TL;DR: In this article, a comprehensive understanding of the fundamentals of the microstructural evolution during FSW/P has been developed, including the mechanisms underlying the development of grain structures and textures, phases, phase transformations and precipitation.

390 citations