Showing papers by "Harpreet Singh Grewal published in 2020"

Enhanced Biocorrosion Resistance and Cellular Response of a Dual-Phase High Entropy Alloy through Reduced Elemental Heterogeneity

Abstract: The leaching out of toxic elements from metallic bioimplants has serious repercussions, including allergies, peripheral neuritis, cancer, and Alzheimer’s disease, leading to revision or replacement...

Biocompatible High Entropy Alloys with Excellent Degradation Resistance in a Simulated Physiological Environment

Abstract: Bioimplants are susceptible to simultaneous wear and corrosion degradation in the aggressive physiological environment. High entropy alloys with equimolar proportion of constituent elements represe...

Complex concentrated alloy bimodal composite claddings with enhanced cavitation erosion resistance

Abstract: In this current study, we developed SiC (10 wt%) reinforced AlCoCrFeNi complex concentrated alloy composite claddings with different particle sizes (micro, nano and bimodal) on stainless steel 316L substrate using microwave irradiation. Microstructural analysis showed cellular structured claddings with intermetallic phases occupying the intercellular regions along with low porosity (

Facile fabrication of superhydrophobic brass surface for excellent corrosion resistance

Abstract: In this study, superhydrophobic surfaces were fabricated using 1H,1H,2H,2H-perfluorooctyltriethoxysilane monolayer deposition on thermally oxidized brass. The superhydrophobic surface showed a cont...

Enhanced cavitation erosion resistance of a friction stir processed high entropy alloy

Abstract: Friction stir processing of an Al0.1CoCrFeNi high entropy alloy (HEA) was performed at controlled cooling conditions (ambient and liquid submerged). Microstructural and mechanical characterization of the processed and as-cast HEAs was evaluated using electron backscat-ter diffraction, micro-hardness testing and nanoindentation. HEA under the submerged cooling condition showed elongated grains (10 µm) with fine equiaxed grains (2 µm) along the boundary compared to the coarser grain (∼2 mm) of as-cast HEA. The hardness showed remarkable improvements with four (submerged cooling condition) and three (ambient cooling condition) times that of as-cast HEA (HV ∼150). The enhanced hardness is attributed to the significant grain refinement in the processed HEAs. Cavitation erosion behavior was observed for samples using an ultrasonication method. All of the HEAs showed better cavitation erosion resistance than the stainless steel 316L. The sample processed under a submerged liquid condition showed approximately 20 and 2 times greater erosion resistance than stainless steel 316L and as-cast HEA, respectively. The enhanced erosion resistances of the processed HEAs correlate to their increased hardness, resistance to plasticity, and better yield strength than the as-cast HEA. The surface of the tested samples showed nucleation and pit growth, and plastic deformation of the material followed by fatigue-controlled disintegration as the primary material removal mechanism.

Facile and Green Engineering Approach for Enhanced Corrosion Resistance of Ni-Cr-Al2O3 Thermal Spray Coatings.

Abstract: Thermal spray coatings (TSCs) are widely utilized for limiting degradation of structural components. However, the performance of TSCs is significantly impaired by its inherent non-homogeneous micro...

Effect of topography and chemical treatment on the hydrophobicity and antibacterial activities of micropatterned aluminium surfaces

Abstract: Superhydrophobic surfaces with high adhesion have attracted huge attention in recent research work due to their versatile applications including transportation of microdroplet without any loss. Modification of metallic surfaces to achieve such properties is important to extend their applications. Especially, the superhydrophobic surfaces with very low bacterial adhesion have attracted intense attention in medical, food, and pharmaceutical industries. Here, we have fabricated different micropatterns on aluminium surfaces using a simple and cost-effective micro-imprinting technique. The surface chemistry was modified through a coating of low surface energy material 1H,1H,2H,2H-Perfluorooctyl-trichlorosilane (FOTS) using vapor deposition technique. Surface morphology of the samples was investigated using scanning electron microscopy (SEM) and contact profilometer. Results show a significant influence of the surface morphology on the wetting, adhesion and anti-bacterial properties. Surfaces composed of discrete micropillars showed higher de-wetting compared to surface containing continuous zig-zag micro lines even despite lower roughness factor. However, the opposite trend was observed in case of adhesion. These results are explained based on wetting state and difference in liquid-air interface pinning. Further, the developed samples showed higher water-retaining ability compared to rose-petal along with superhydrophobicity. The surface with micropillar structures with higher roughness factor exhibited improved non-fouling behavior which has been quantified by spot assays and atomic force microscopy (AFM). This study opens up the possibility of fabricating multifunctional metal surfaces on a large scale by a cost-effective, environment friendly and easily scalable processing route.

Enhanced Cavitation Erosion–Corrosion Resistance of High-Velocity Oxy-Fuel-Sprayed Ni-Cr-Al 2 O 3 Coatings Through Stationary Friction Processing

Abstract: Cavitation erosion is a huge problem in engineering structures working under hydrodynamic conditions. The synergistic effect of erosion and corrosion can aggravate the material removal by several orders of magnitude. Surface coatings are widely used to address material degradation by erosion–corrosion. However, non-homogenous microstructure and presence of defects leads to premature coating failure under erosion–corrosion conditions. Thus, it is imperative to identify plausible solutions to address cavitation-related material degradation. In this study, Ni-Cr-5Al2O3 coatings were deposited on stainless steel substrate using high-velocity-oxy-fuel technique. The as-sprayed coating showed highly non-homogeneous microstructure comprising splats, pores, intermetallic compounds and elemental segregation. A new thermo-mechanical processing technique, stationary friction processing (SFP), was utilized for achieving through-thickness microstructural refinement in as-sprayed coating. As-sprayed and SFP-treated coatings were tested in pure cavitation erosion, corrosion in 3.5% NaCl solution and erosion–corrosion. SFP treatment resulted in 5-times enhancement in the erosion and corrosion resistance compared to as-sprayed coating. The remarkable performance of Ni-Cr-5Al2O3 coatings after SFP treatment is attributed to significant enhancement in the mechanical properties including hardness and fracture toughness which is the consequence of complete removal of splat boundaries, pores, intermetallic compounds and uniform element distribution up to the coating–substrate interface.

Structural rejuvenation of thermal spray coating through stationary friction processing

Abstract: In this study, a novel processing technique for microstructural refinement of Ni-Cr-5Al2O3 composite coating developed using high velocity oxy-fuel (HVOF) technique is demonstrated. The processing technique, known as stationary friction processing (SFP) is an adaptation of the well-known friction stir processing (FSP). The as-sprayed coating showed a typical lamellar microstructure along with non-homogeneous elemental distribution. The SFP treatment resulted in significant microstructural refinement with complete elimination of splat boundaries and pores together with fully homogeneous elemental distribution. The performance of as-sprayed and processed coatings was evaluated in slurry erosion, erosion-corrosion and pure corrosion in 3.5% NaCl solution. At oblique impingement angle, the SFP treated sample showed minimum erosion rate of nearly 0.1 mm3/h which is 3–5 times lower than the as-sprayed coating and the substrate. For normal impingement, the erosion rate of SFP specimen was nearly 30% lower compared to the as-sprayed coating and the substrate. This is attributed to higher hardness as well as fracture toughness of the SFP treated coating as a result of microstructural refinement. In addition, the SFP treated coating was able to demonstrate superior resistance under erosion-corrosion conditions as well. Further, the processed sample showed lowest corrosion rate of 0.079 μA/cm2, 5–6 times lower than the as-sprayed coating (0.39 μA/cm2). The enhancement in the corrosion resistance of the coating after processing is attributed to complete homogenization of the coating with removal of all splats, splat boundaries, pores and regions of elemental segregation.

Effect of Some Additives on Tribological Properties of SAE20W40 Lubricant

Abstract: Friction and wear loss of various machining parts and pairs depend majorly on the quality of lubricants. Several types of additives are commercially used to enhance the tribological performance of a lubricant. In the present work, some novel lubricating liquids were prepared by mixing diffident additives, viz bromide, fluoride, iodide and acetate, in a commercial available SAE20W40 lubricant. Pin-on-disc investigations were performed to evaluate the effect of the prepared lubricants on wear rate and friction characteristics of mild steel and stainless steel sliding pair. Disc chamber was flooded with lubricants during testing. Fluoride was found to be the most successful additive to improve the performance of the given lubricant, whereas acetate as an additive made the base lubricant less efficient. It is believed that the strong bond stability of C–F bond during working conditions resulted in better performance of the lubricant after the addition of fluoride.