Surface Modification of AISI 1020 Mild Steel by Electrical Discharge Coating with Tungsten and Copper Mixed Powder Green Compact Electrodes

Electro discharge machining (EDM) is a non- conventional machining process, which is widely used for machining of very hard materials used for engineering purposes. In Electrical Discharge Coating (EDC) process tool electrode which is manufactured by powder metallurgy (P/M) technique, connected to anode and work-piece (on which coating is to be done) is selected as cathode in electro discharge machine (polarity opposite to the electrical discharge machining). In presence of dielectric, tool electrode is worn out during EDM and the material removed from the surface of electrode deposited over the work-piece surface. This project work describes an advanced method of surface modification by Electrical Discharge Coating (EDC). In this work Tungsten carbide and Copper (WC- Cu) composite coating deposited on AISI 1020 mild steel substrate. Tungsten (W) and Copper (Cu) powder in different weight percentages has been used for preparation of tool electrode by P/M process. Effect of compact pressure, proportions of powder of materials (during tool preparation) and peak current (during EDC) on deposition rate of the coating and tool wear rate has been investigated. By using X-Ray Diffraction (XRD) technique different phases formed in the deposited layer during the process has been identified. Scanning Electron Microscopy (SEM) has been done to reveal the microstructure of the coated surface. Vickers‟ Micro hardness testing has been performed on the coating to measure the hardness values of coated surface

Laser machining of zirconia green compacts to produce cavities and blocks: parametric optimization and patterning

Zirconia is a very popular material among implants and prosthesis, due to its antibacterial activity, corrosion resistance and hardness properties. For these purposes, zirconia is to be sintered beforehand to obtain good dimensional and geometrical accuracy and then machined. However, the machining of sintered zirconia has always been a troublesome proposition, attributable to its extreme hardness. The excellent properties of zirconia were applied in this study to the cutlery design. Nowadays, cutlery/flatware designs are constantly changing. However, for manufacturing, the traditional molding process remains widely popular, despite having huge limitations regarding aesthetic and design flexibility. In the present study, we explore a new horizon of cutlery design by patterning using laser surface modification. Blocks were laser machined from zirconia green compacts, which solved the machining problems associated with sintered zirconia, and then inserted into stainless-steel cutlery grooves to produce a novel aesthetical cutlery design. This study addresses the parametric optimization of laser parameters (power, scanning speed and number of passages) to produce cavities in zirconia green compacts. Material removal, depth of cut, geometry and surface roughness were taken as output variables. For the analyses, a full factorial design of experiments was adopted. Moreover, this study provides the optimum parameters for the laser machining of zirconia green compacts to produce blocks with accurate dimensions and geometries. After laser machining the zirconia blocks, sintering was performed to achieve the desired dimensions.publishe

Nature inspired wet adhesive E-Skin patch for biosensing applications

Tree frogs are able to climb or stick to wet and rough surfaces. The hexagonal epithelial cells enclosed by profound passages which shield the surface of each toe pad and the array of nano-pillars on their surface are the main reason for their outstanding reversible adhesion in wet and rough environment. Inspired by the frog toe pad hexagonal hierarchical micro-pillars are developed by using Silicon rubber/ZrO2 nanocomposite. Due to the addition of oxide nanoparticles wettability properties of the rubber enhanced. The interlocking structures and hexagonal pattern helps to improve the capillary action and the sweat/water particles are drained easily, as a result surface adhesion increases. To design the hexagonal micro-pillars innovative laser engraving technique is adopted. The homogeneous distribution of nanoparticles and hierarchical hexagonal micro-patterns are confirmed through SEM analysis. This innovative design approach is helpful to design E-skin adhesive wearable devices for accurate monitoring of physiological signals.This work is supported by National Funds through the Portuguese Science Foundation (FCT) within project “FCT Reference No.: 030353 of IC&DT - AAC No. 02 / SAICT / 2017”, co-financed by the European Regional Development Fund (ERDF), through the Operational Programme for Competitiveness and Internationalization (COMPETE 2020), under Portugal 2020. Finally, this work was supported by FCT national funds, under the national support to R&D units grant, through the reference projects UIDB/04436/2020 and UIDP/04436/2020

Laser surface texturing of stainless-steel cutlery to integrate ceramic blocks: parametric optimization and patterning

Dynamic and fast-changing designs for cutleries or flatware are one important nature of this production business. Globalized hospitality merchandise, the demanding nature of modern customers, throat-to-throat competition of manufacturing industries, and the modernization of the manufacturing processes are some of the major challenges for the cutlery (silverware) manufacturing industry. So far, traditional methods of moulding and shaping are considered to be the best to provide static designs and trademark patterns of the organisation. Preparing a designed mould for a fixed blueprint of cutlery and then producing it in bulk is the sole purpose of existing methods. However, with the invention of laser engraving and design systems, the entire business of cutlery production has revolutionized. Allowing for different designs for different cutleries to set without changing the whole production line was the aim of this study. As shown in Figure 1, AISI-304 stainless steel, which is the general flatware material selected for laser engraving, was evaluated with three most vital input parameters (power, scanning speed and loops or number of passes) followed by the analysis of geometry, roughness, and volume removed/material removal (MR) as output variables. This study will provide insight into the know-how situation involving the processing of cutleries and introduction of different ceramic materials to the surface to define desired patterns. We produced different design patterns by laser and ingrained ceramic blocks on the silverware. This approach is much more flexible and adoptable for pattern changes. Besides that, there is no need to prepare a mould for each design. Belo Inox, Portugal supplied the silverware as per the collaborative project agreement.publishe

A nature-inspired superhydrophilic nano-powder based silicone rubber composite

Silicone-Rubber (SR) is an elastomer prominently used in biomedical and medical devices, implants, and winter shoe industries because of its stability, durability, friction properties, biocompatibility, anti-bacterial, temperature resistance, and hypoallergenic characteristics. However, inherent hydrophobicity limits the use of SR as it cannot form a protective liquid layer for implants and medical devices while placed internally or externally and impairs tissue adhesion as well. Moreover, hydrophobicity reduces ice adhesion strength in the absence of capillary bridges and that makes winter shoe-soles more slippery. The physical and chemical solutions like oxidation, UV, plasma, corona discharge, gamma radiation, and Laser radiation grafting to turn SR into hydrophilic are either temporary or change the bulk properties of the compounds. We propose an innovative multifunctional SR composite incorporating zirconia and/or titania nanoparticles produced by roller mixing followed by hot compression moulding (pressure/heating vulcanisation). Subsequently, nature-inspired patterns like gecko or frog toepads are produced on SR compound by Laser-Surface-Texturing (LST) to expose the nanoparticles that attract water molecules. A parametric optimisation along with nano-powder percentage decides the wettability of the composite. A permanent superhydrophilic SR compound was produced that can be further used to increase ice adhesion to manufacture anti-slipping winter shoe-soles or other biomedical applications.This work was supported by Foundation for Science and Technology (FCT) national funds, under the national support to R&D units grant. The work is supported by the project “BioInSole-Multi-Functional Bioinspired Slip Resistant Shoe-Sole” under the reference UIDP/04436/2020 and Association for Innovation and Development from FCT (Caparica) (PTDC/EME-EME/7860/2O20). Vipin Richhariya also acknowledges FCT for his individual PhD scholarship through “Design and development of multifunctional surfaces to control friction behaviour in the presence of water” under the reference UI/BD/150939/2021

A Bio-inspired anti-slipping winter shoe-sole

Hundreds of thousands of people injure every year due to Slips and Falls (SF) around the globe. The SF on ice during wintertime is an inevitable proposition. Though SF injuries don’t seem concerning, it ranks second among the causes of injuries in the world claiming billions of euros and thousands of lives. The staggering outcomes of SF are loss of jobs (for the people getting injured), loss of skilled workers (for the companies which trained the worker), expenses on the healthcare, burden on the insurance companies and social securities. To reduce SF, anti-slipping shoe-soles are used, however, existing soles provide very limited rescue from the slippage. Moreover, existing solution either modify material or tread design to increase friction on the icy surfaces. In this work, nature-inspired anti-slipping winter shoe-soles are being explored that combine material and tread design variation together using Laser Surface Texturing (LST) to obtain higher friction.This work was supported by FCT national funds, under the national support to R&D units grant, through the reference projects UIDB/04436/2020 and UIDP/04436/2020. We also acknowledge the project “BioInSole-Multi-Functional Bioinspired Slip Resistant Shoe-Sole” Associação para a Inovação e Desenvolvimento da FCT (Caparica) (PTDC/EME-EME/7860/2O20) and Vipin Richhariya acknowledges FCT for his PhD scholarship through “Projeto e Desenvolvimento de Superfícies Multifuncionais para Controlo do Comportamento à Fricção na Presença de Água (UI/BD/150939/2021)

Anti-slipping winter shoe-soles: a nature-inspired solution

Apresentação efetuada em "Junior Euromat 2022", em Coimbra, 2022This work was supported by FCT national funds, under the national support to R&D units grant, through the reference projects UIDB/04436/2020 and UIDP/04436/2020, “BioInSole-Multi-Functional Bioinspired Slip Resistant Shoe-Sole” Associação para a Inovação e Desenvolvimento da FCT (Caparica) (PTDC/EME-EME/7860/2020) , and Vipin Richhariya acknowledges FCT for his PhD scholarship through “Projeto e Desenvolvimento de Superfícies Multifuncionais para Controlo do Comportamento à Fricção na Presença de Água (UI/BD/150939/2021)”

Tribological performance of laser-textured steel surfaces in unidirectional sliding line-contact (block-on-ring)

The following theoretical and experimental work presents a study on the influence of texture parameters on the tribological performance of dimpled steel surfaces. Different texture parameters were selected through hydrodynamic lubrication modeling based on the two-dimensional Reynolds equation and literature search. For the experimental work, microscopic spherical cavities (i.e., dimples) were created by laser on 25 mm steel discs. The textured specimens were tested in a unidirectional sliding line-contact block-on-ring set-up at different rotational speeds. The experiments showed that the area-density-ratio, dimple-depth, and dimple-diameter can significantly affect the tribological performance of steel surfaces. Specimens containing dimples with lower depth, lower area-density-ratio, and smaller diameters, exhibited significant improvements over a smooth steel surface. The most remarkable achievement was a 28.6% friction reduction at 20 RPM and an overall improvement of 13% considering all speeds.The authors would like to acknowledge the financial support from the projects: ATRITO-0 [co-financed via FEDER (PT2020) POCI-01-0145-FEDER-030446 and FCT (PIDDAC)], On-SURF [co-financed via FEDER (PT2020) POCI-01-0247-FEDER-024521], and CEMMPRE UID/EMS/00285/2019 [co-financed via FEDER and FCT (COMPETE)]

Unravelling the physics and mechanisms behind slips and falls on icy surfaces: a comprehensive review and nature-inspired solutions

Slip and Fall (SF) on slippery icy/snowy surfaces during winters is evident worldwide, especially in Nordic regions. Every year millions of people slip and fall due to ice accretion on the roads, streets, and pavements causing traumatic injuries, loss of limbs, and sometime loss of lives, costing billions in hospitals and recovery. An efficient anti-slipping winter shoe-sole could prevent these accidents and save lives. Footwear industries came up with solutions such like crampons, cleats, anti-skidding materials and tread pattern designs, but with limited success because of their ineffectiveness on wet ice, quick rate of wearing. The inspiration from nature like polar bear, seal, arctic fox, penguin, snake, octopus, frog, and gecko where this problem is elegantly solved through evolution process can address these limitations and design advanced anti-slippery surfaces. The review presents a comprehensive understanding of biological designs of the footpads (polar bear, penguin, arctic fox, frog, gecko) and skins (seal, snake, octopus’ suction cups) and recent progress on their translation for practical applications. The review emphasises on the mechanisms of icy slippery surfaces and the contact surfaces (shoe-sole and ice/snow) to mimic anti-slipping mechanism of animals and their movement on ice enabling to design the finest anti-slipping winter shoe-soles.This work is supported by the Foundation for Science and Technology (FCT) Portugal under the national support to R&D units’ grant through the reference project UIDB/04436/2020 and UIDP/04436/ 2020 and through the project “BioInSole-Multi-Functional Bioinspired Slip Resistant Shoe-Sole” with grant reference PTDC/EME-EME/7860/ 2020. VR acknowledges support from FCT for his individual PhD grant under the reference UI/BD/150939/2021. DL and MJN acknowledge support form Australian Research Council, ARC, (IH 150100003 and IH 120100025)

Synergic effect of TMD coating on textured steel using micro-EDM

Modifying the surface of materials through texturing and coating can have a significant impact on their tribological properties. In the present study, a hybrid surface modification process, texturing combined with coating, has been applied to a steel surface and the tribological behavior in lubricated conditions was studied. The surface of the steel was textured using micro-electric discharge machining (micro-EDM) to create two distinct patterns (rectangular and circular). Following this, transition metal dichalcogenides (TMD); tungsten-sulphur‑carbon (WSC) coating was applied to the surface using magnetron sputtering. To evaluate the specimens, they were subjected to tribological testing in various lubrication conditions using a block-on-ring configuration. The results were corroborated using a reciprocating sliding test and compared to those of a smooth uncoated specimen. The findings revealed that the tribological properties of the textured and coated specimens were enhanced, particularly in specimens with circular dimple patterns. The WSC coated circular dimple specimens showed a reduction of the COF by 7–12 %, in the boundary lubrication regime and by 9–25 %, in the mixed and hydrodynamic lubrication regimes as compared to the untreated specimen.The authors record sincere thanks to the University of Minho, Instituto Pedro Nunes and CEMMPRE for extending its facilities. This work is sponsored by FEDER and by National funds through FCT- Fundação para a Ciência e a Tecnologia under the projects: ON-SURF ref. “POCI-01- 0247-FEDER-024521”, ATRITO-0 ref. “POCI-01-0145-FEDER-030446”, CEMMPRE ref. “UIDB/00285/2020” and ARISE ref. “LA/P/0112/ 2020”