Laser Texturing to Increase the Wear Resistance of an Electrophoretic Graphene Coating on Copper Substrates.

In the present paper, different surface preparations are investigated with the aim of increasing the wear behaviour of an electrophoretic graphene coating on a copper plate. The study was divided into two steps: In the first step (pre-tests), to detect the most promising pretreatment technology, five different surface preparations were investigated (electropolishing, sandblasting, degreasing and pickling, laser cleaning and laser dots).In the second step, on the basis of the results of the first step, a 32 full factorial plan was developed and tested; three treatment types (pickled and degreased, laser-cleaned, and laser dots) and three different voltages (30, 45 and 60 V) were adopted. Analysis of variance (ANOVA) was used to evaluate their influence on wear resistance; in particular, the maximum depth and width of the wear tracks and the coating break distance were investigated. The results of this study show that, in optimal conditions, laser treatment (particularly laser dots) canlead to as high as a four-fold increase in wear resistance.

Study on Pulse-Reverse Electroplating Process for the Manufacturing of a Graphene-Based Coating.

This work investigates the feasibility of increasing the electric conductivity of an AA1370 aluminium wire by using pulse-reverse electrodeposition to realize Cu-Graphene composite coating. The graphene adopted was in the form of nanoplates (GnP). To study the effects of plating parameters, a 23 factorial plan was developed and tested. During the tests, the following process parameters were varied: the current density, the frequency and the duty cycle. The ANalysis Of VAriance (ANOVA)) was adopted to evaluate their influence on the coated wires' morphology and electrical conductivity resistance. The results show that all the tested conditions allow good compactness to the coating, and the amount of graphene is well incorporated within the microstructure of the copper deposit. In addition, in the best conditions, the electrical resistivity decreases up to 3.4% than the uncoated aluminum.

Surface Finishing of Additive Manufactured Ti-6Al-4V Alloy: A Comparison between Abrasive Fluidized Bed and Laser Finishing.

Metal additive manufacturing is a major concern for advanced manufacturing industries thanks to its ability to manufacture complex-shaped parts in materials that are difficult to machine using conventional methods. Nowadays, it is increasingly being used in the industrial manufacturing of titanium-alloy components for aerospace and medical industries; however, the main weakness of structural parts is the fatigue life, which is affected by surface quality, meaning the micro-cracking of small surface defects induced by the manufacturing process. Laser finishing and Abrasive Fluidized Bed are proposed by the authors since they represent cost-effective and environment-friendly alternatives for automated surface finishing. A comparison between these two finishing technologies was established and discussed. Experimental tests investigated both mechanical properties and fatigue performances. The tests also focused on understanding the basic mechanisms involved in fatigue failures of machined Ti-6Al-4V components fabricated via Electron Beam Melting and the effects of operational parameters. X-ray tomography was used to evaluate the internal porosity to better explain the fatigue behaviour. The results demonstrated the capability of Laser finishing and Abrasive Fluidized Beds to improve failure performances. Life Cycle Analysis was additionally performed to verify the effectiveness of the proposed technologies in terms of environmental impact and resource consumption.

Soft Computing Techniques for Laser-Induced Surface Wettability Control.

Making decisions and deducing control actions in manufacturing environments requires considering many uncertainties. The ability of fuzzy logic to incorporate imperfect information into a decision model has made it suitable for the optimization of both productivity and final quality. In laser surface texturing for wettability control, in fact, these aspects are governed by a complex interaction of many process parameters, ranging from those connected with the laser source to those concerning the properties of the processed material. The proposed fuzzy-based decision approach overcomes this difficulty by taking into account both the random error, associated with the process variability, and the systematic error, due to the modelling assumptions, and propagating such sources of uncertainties at the input level to the output one. In this work, the laser surface texturing was carried out with a nanosecond-pulsed laser on the surfaces of AISI 304 samples, changing the laser scanning speed, the hatch distance, the number of repetitions, and the scanning pattern. A significant change of the contact angle in the range 24-121° is observed due to the produced textures. The fuzzy maps highlight the inherent uncertainty due to both the laser texturing process and the developed model.

Combined Fuzzy and Genetic Algorithm for the Optimisation of Hybrid Composite-Polymer Joints Obtained by Two-Step Laser Joining Process.

In the present work, genetic algorithms and fuzzy logic were combined to model and optimise the shear strength of hybrid composite-polymer joints obtained by two step laser joining process. The first step of the process consists of a surface treatment (cleaning) of the carbon fibre-reinforced polymer (CFRP) laminate, by way of a 30 W nanosecond laser. This phase allows removing the first matrix layer from the CFRP and was performed under fixed process parameters condition. In the second step, a diode laser was adopted to join the CFRP to polycarbonate (PC) sheet by laser-assisted direct joining (LADJ). The experimentation was performed adopting an experimental plan developed according to the design of experiment (DOE) methodology, changing the laser power and the laser energy. In order to verify the cleaning effect, untreated laminated were also joined and tested adopting the same process conditions. Analysis of variance (ANOVA) was adopted to detect the statistical influence of the process parameters. Results showed that both the laser treatment and the process parameters strongly influence the joint performances. Then, an uncertain model based on the combination of fuzzy logic and genetic algorithms was developed and adopted to find the best process parameters' set able to give the maximum joint strength against the lowest uncertainty level. This type of approach is especially useful to provide information about how much the precision of the model and the process varies by changing the process parameters.

Improving Performance of an Open Cell Aluminium Foam through Electro-Deposition of Nickel.

The aim of this work is to investigate the mechanical performances and corrosion resistance of open-cell aluminium foams with an electroplated nickel coating. The influence of two different electrolytic solutions on mechanical properties and corrosion resistance was studied: The Watts solution (nickel sulphate-based solution) and a nickel sulphamate solution (widely adopted). Scanning electron microscopy and stereoscopic analysis allowed for the estimation of the coating uniformity and adhesion to the substrate. In order to assess the improvement of performances, compression and corrosion tests were performed on coated and uncoated foams. In addition, annealing was investigated in relation to different operational parameters, related both to electro-deposition (electrolyte, deposition current and time) and to annealing (treatment temperature). From the results, the yield stress and the corrosion resistance improved. Moreover, the annealing at increasing temperature was found to reduce the yield stress, but Ni-coated foams showed higher values of stress for all the considered treatment temperatures.