H.S. Grewal
Shiv Nadar University
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Featured researches published by H.S. Grewal.
Tribology Letters | 2013
H.S. Grewal; Anupam Agrawal; Harpreet Singh
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.
Journal of Thermal Spray Technology | 2014
H.S. Grewal; Anupam Agrawal; Harpreet Singh; Barbara A. Shollock
In this paper, slurry erosion performance of high velocity flame-sprayed Ni-Al2O3 based coatings was evaluated. The coatings were deposited on a hydroturbine steel (CA6NM) by varying the content of Al2O3 in Ni. Using jet-type test rig, erosion behavior of coatings and bare steel was evaluated at different impingement angles. Detailed investigation of the surface morphology of the eroded specimens was undertaken using SEM/EDS to identify potential erosion mechanism. A parameter named “erosion mechanism identifier” (ξ) was used to predict the mode of erosion. It was observed that the coating prepared using 40xa0wt.% of Al2O3 showed a highest resistance to erosion. This coating enhanced the erosion resistance of the steel by 2 to 4 times. Spalling in the form of splats and chunks of material (formed by interlinking of cracks) along with fracture of Al2O3 splats were identified as primary mechanisms responsible for the loss of coating material. The erosion mechanism of coatings and bare steel predicted by ξ was in good agreement with that observed experimentally. Among different parameters,
Ultrasonics Sonochemistry | 2018
Rakesh B. Nair; Harpreet Singh Arora; Sundeep Mukherjee; S. Singh; Harpreet Singh; H.S. Grewal
Scientific Reports | 2015
H.S. Grewal; Hong Nam Kim; Il-Joo Cho; Eui-Sung Yoon
left( {K_{text{IC}}^{2} H} right)^{1/3}
Bioinspiration & Biomimetics | 2015
H.S. Grewal; Il-Joo Cho; Eui-Sung Yoon
Surface Engineering | 2014
H. S. Arora; H.S. Grewal; M. Veligatla; Harpreet Singh; S. Mukherjee
KIC2H1/3, a function of fracture toughness (KIC) and hardness (H) showed excellent correlation with erosion resistance of coatings at both the impingement angles.
Transactions of The Indian Institute of Metals | 2012
H.S. Arora; Harpreet Singh; B. K. Dhindaw; H.S. Grewal
Cavitation erosion and corrosion of structural materials are serious concerns for marine and offshore industries. Durability and performance of marine components are severely impaired due to degradation from erosion and corrosion. Utilization of advanced structural materials can play a vital role in limiting such degradation. High entropy alloys (HEAs) are a relatively new class of advanced structural materials with exceptional properties. In the present work, we report on the cavitation erosion behavior of Al0.1CoCrFeNi HEA in two different media: distilled water with and without 3.5wt% NaCl. For comparison, conventionally used stainless steel SS316L was also evaluated in identical test conditions. Despite lower hardness and yield strength, the HEA showed significantly longer incubation period and lower erosion-corrosion rate (nearly 1/4th) compared to SS316L steel. Enhanced erosion resistance of HEA was attributed to its high work-hardening behavior and stable passivation film on the surface. The Al0.1CoCrFeNi HEA showed lower corrosion current density, high pitting resistance and protection potential compared to SS316L steel. Further, HEA showed no evidence of intergranular corrosion likely due to the absence of secondary precipitates. Although, the degradation mechanisms (formation of pits and fatigue cracks) were similar for both the materials, the damage severity was found to be much higher for SS316L steel compared to HEA.
Science and Technology of Advanced Materials | 2014
Harpreet Singh Arora; Sanghita Mridha; H.S. Grewal; Harpreet Singh; Douglas C. Hofmann; Sundeep Mukherjee
We investigate the role of viscous forces on the wetting of hydrophobic, semi-hydrophobic, and hydrophilic textured surfaces as second-order effects. We show that during the initial contact, the transition from inertia- to viscous-dominant regime occurs regardless of their surface topography and chemistry. Furthermore, we demonstrate the effect of viscosity on the apparent contact angle under quasi-static conditions by modulating the ratio of a water/glycerol mixture and show the effect of viscosity, especially on the semi-hydrophobic and hydrophobic textured substrates. The reason why the viscous force does not affect the apparent contact angle of the hydrophilic surface is explained based on the relationship between the disjoining pressure and surface chemistry. We further propose a wetting model that can predict the apparent contact angle of a liquid drop on a textured substrate by incorporating a viscous force component in the force balance equation. This model can predict apparent contact angles on semi-hydrophobic and hydrophobic textured surfaces exhibiting Wenzel state more accurately than the Wenzel model, indicating the importance of viscous forces in determining the apparent contact angle. The modified model can be applied for estimating the wetting properties of arbitrary engineered surfaces.
Advanced Materials Research | 2012
H.S. Grewal; H. Singh; Anupam Agrawal; H.S. Arora
Superhydrophobicity facilitates the development of self-cleaning, anti-biofouling, and anti-corrosion surfaces. The leaves of the lotus (Nelumbo nucifera) and taro (Colocasia esculenta) plants are well known for their self-cleaning properties. A hierarchical structure comprising papillae epidermal cells superimposed with epicuticular wax crystalloids of varying shapes, sizes, and orientations is an important aspect of the surface of these plant leaves. We fabricated two types of hierarchical structures biomimicking the surface topography of the lotus leaf. The hierarchical patterns successfully demonstrated the superhydrophobic state in comparison with nano and micro patterns. We used the finite element method (FEM) to simulate and understand the wetting process. The FEM simulations showed good correlation with the experimental results. FEM was helpful in understanding the wetting of enormously complex biological surfaces with relative ease, and it qualifies as a potential tool for designing superhydrophobic surfaces. Using the FEM framework, we further designed surfaces to optimize the order of the shapes in hierarchy. The results showed that the superhydrophobic surface with the lowest wetted area was obtained by placing shapes with smaller geometric angles at the top of the hierarchy. This arrangement of shapes provides the optimum combination of superhydrophobicity and surface integrity. This observation explains why the hierarchical structure of many superhydrophobic leaves follows this order. We also investigated the complex hierarchical structure of Salvinia minima. Owing to its remarkable ability to entrap air and pin the contact line, it exhibits superhydrophobicity along with the much-required Cassie state. These properties of Salvinia minima make it an excellent candidate for developing omniphobic surfaces.
Advances in Friction-Stir Welding and Processing | 2014
H.S. Arora; H.S. Grewal; Harpreet Singh; B. K. Dhindaw
Abstract An in situ composite coating on pure aluminium substrate was prepared by novel microwave processing of iron based metallic glass powder precursor. The microstructure obtained after processing comprised of a molybdenum rich harder phase uniformly distributed in iron rich softer phase. The hardness and modulus of each phase were obtained by nanoindentation. Scratch test across the substrate coating indicated good interface strength and strong adhesion of the coating with the substrate.