Browsing by Author "Walczak, M."
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- ItemA method for manufacturing cellular metals with open- and close-type porosities(ELSEVIER SCIENCE BV, 2011) Covaciu, M.; Walczak, M.; Ramos Grez, J.New approach for manufacturing metallic cellular materials with controlled open pore geometry and cells arrangement is presented. The method is based on the combination of rapid prototyping of a template with powder metallurgy. Modification of the procedure allows for additional introduction of closed-type porosity with pores smaller than those defined by the rapid prototyped template. The accuracy of the method for controlling the size, shape and arrangement of open-type pores is presented on the example of zinc with an inorganic template (CuSO(4)). The same materials are used to produce a structure with two types of porosities combined in one structure, regular opened and irregular closed. The control of pore geometry allows for optimization of metallic cellular materials for their mechanical, chemical and biological applications. (C) 2011 Elsevier B.V. All rights reserved.
- ItemA novel one-pot method to synthesize hierarchical mesoporous carbon foams with ZnO coating(2019) Covaciu, Manuela; Ramos Moore, Esteban; Rojas, S.; Lastra, N.; Armijo, F.; Walczak, M.
- ItemApplicability of LPBF for producing Cu-11Al-5Ni-4Fe wt.% with shape memory properties(2023) Guerra, C.; Ramos Grez, Jorge; La Fe-Perdomo, I; Castillo, A.; Walczak, M.
- ItemBiofilm development and biocorrosion of stainless steel AISI 316L exposed to marine conditions(2015) Paille, L.; Irre, J.A.; Fischer, P.; Galarce, C.; Walczak, M.; Armijo, F.; Pizarro, G.; De La Iglesia, R.; Vargas Cucurella, Ignacio Tomas
- ItemCorrosion behavior of stainless steel AISI 470 in pacific seawater(2015) Aguirre, J.; Walczak, M.; Armijo, F.; Daille, L.; Fischer, D.; Galarce, C.; De La Iglesia, R.; Pizarro, G.; Vargas Cucurella, Ignacio Tomas
- ItemErosion by turbulence: Discovering the counter-wise vortex events and their effect on wear(2023) Espinoza-Jara, A.; Walczak, M.; Brevis Vergara, Wernher Ariel; Messa, G.V.
- ItemErosion under turbulent flow: a CFD-based simulation of near-wall turbulent impacts with experimental validation(2022) Espinoza-Jara, A.; Walczak, M.; Molina, N.; Jahn, W.; Brevis Vergara, Wernher Ariel
- ItemNITRIDING OF SUPER-FERRITIC STAINLESS STEEL BY PLASMA IMMERSION ION IMPLANTATION IN RADIO FREQUENCY AND ECR-MICROWAVE PLASMA SYSTEM(IEEE, 2015) Bhuyan, H.; Favre, Mario; Cisternas, M.; Henriquez, A.; Wyndham, E.; Mandl, S.; Manova, D.; Walczak, M.Stainless steel 470 Li-24 Cr and 460Li-21 Cr are two new generation super-ferritic nickel free grades, contains titanium (Ti), niobium (Nb) and very small percentage of carbon (C) and nitrogen (N). The Ti and Nb enhance the corrosion resistance while the low interstitial content of C and N leads to finer precipitates and greater ductility. These grades are economic alternative to 316L and 304 with corrosion resistance comparable or superior. However, as 316L and 304 can be nitrided efficiently to improve the mechanical surface properties like hardness and wear; it has to be asked whether these new generation super-ferritic grade stainless steels can be improved further by plasma nitriding too. Two sets of experiments have been carried out, one with capacitively coupled radio frequency Plasma at PUC Chile and the other is microwave plasma at IOM Leipzig, to investigate further improvements in the mechanical properties of 470 Li-24 Cr and 460Li-21 Cr steel. Nitrided and unnitrided substrates are further investigated using different surface characterization techniques including secondary ion mass spectroscopy, scanning electron microscopy, energy dispersive x-ray analysis, Vickers hardness, wear resistance, corrosion test etc. In most of the characterizations the nitrided 470 Li-24 Cr and 460Li-21 Cr shows similar results. Increase of surface roughness for higher treatment temperature is observed in both the experiments, independent of the steel types. The formation of chromium nitride compound takes place at treatment temperature around 400 o C-450 o C, and it increases with further increase in temperature. But at higher temperature corrosion property deteriorate. The characterization results show up to 25% of nitrogen, 4-5 times increased in hardness and diffusion of nitrogen layer up to 4-6 micron for different experimental conditions. The samples implanted with temperature higher than 400°C presented wear resistance values around two orders of magnitude higher than the others.
- ItemPoly(3,4-ethylenedioxythiophene) used as a coating on stainless steel AISI 470. Evaluation of corrosion inhibition performance(2015) Aguirre, J.; Armijo, F.; Walczak, M.; De La Iglesia, R.; Pizarro, G.; Vargas Cucurella, Ignacio Tomas
- ItemQuantifying the effect of copper corrosion scales on passivation(2015) Fischer, D.A.; Galarce, C.A.; Walczak, M.; Vargas Cucurella, Ignacio Tomas; Pizarro, G.E.
- ItemSensitization of AISI 302 stainless steel during low-power laser forming(ELSEVIER SCI LTD, 2010) Walczak, M.; Ramos Grez, J.; Celentano, D.; Lima, E. B. F.Low-power laser forming by raster scanning is a promising technology for shaping thin sheets in a non-contact manner, using a laser beam scanned over the surface. In this work, the change of material microstructure and the related corrosion behavior are investigated in the context of local temperature evolution during the scanning action. Graphite coated AISI 302 stainless steel coupons have been bent to different angles using a 60 W CO2 laser and the resulting cyclic polarization behavior in sulfuric acid was measured. The so revealed sensitization of the material is discussed on the basis of microstructural changes caused by temperature-induced phase transformations. The total times of permanence at temperatures favoring specific transformations were obtained by numerical simulation of the process. It was found that even when no surface melting takes place the recurrent rise of temperature within the material is sufficient to sensitize the non-irradiated side. This effect might be a limiting factor in applications of laser formed AISI 302 in corrosive environments. (c) 2010 Elsevier Ltd. All rights reserved.
- ItemSolar pond technology for large-scale heat processing in a Chilean mine(AMER INST PHYSICS, 2012) Garrido, F.; Soto, R.; Vergara, J.; Walczak, M.; Kanehl, P.; Nel, R.; Garcia, J.Copper mining is the largest industrial activity in Northern Chile, a region that relies mostly on imported energy resources thus making the mining sector vulnerable to the rising cost of fuel oil and electricity. The extraction of copper is mostly accomplished by hydrometallurgy, a three-step low energy process consisting of heap leaching, concentration by solvent extraction, and metal recovery by electro-winning. Since the content of copper in its ore tends to degrade as the mining operation proceeds, higher leaching temperatures would be needed along with increasing energy requirements. In order to address this demand and considering that the region has one of the highest levels of solar radiation and clear skies, the authors assessed the solar pond technology for rising the temperature of the leaching stream. The working principle of such technology is presented, as well as its mathematical formulation, restrictions, and assumptions, aiming to simulate the performance of a solar pond and to size a suitable setup. The results indicate that this technology can provide sufficient heat to raise the temperature to a range of 50 to 70 degrees C throughout the year with an annual gross thermal supply of 626 GWh. In order to minimize the loss of water and salt from the pond, a closed salt cycle is suggested. Savings of up to 59 000 tons of diesel oil per year and the avoidance of 164 000 tons of CO2 per year could be achieved with a solar pond effective area of 1.43 km(2) reaching an average efficiency of 19.4%. Thus, solar pond technology is suitable for attaining the goal of increasing the leaching temperature while diminishing fuel costs and greenhouse emissions. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4757627]
- ItemSurface Hardness of Mild Steel (AISI/SAE 1020) after Direct Laser Surface Alloying with Chromium(2013) Olivos, A.; Ramos Grez, Jorge; Walczak, M.