1,721,095 research outputs found
Corrosion resistance in different environments of Ni Matrix Micro- and nano-composite electrodeposits
No full textThe galvanic codeposition of ceramic particles for the production of metal matrix composite coatings is a research domain of wide interest as these deposits could be used for a large field of applications, especially in cases where high wear and corrosion resistance are required. The aim of this work is the production and characterization of nickel matrix micro- and nano-composite deposits. Three types of deposits have been produced: pure Ni deposits, Ni containing SiC microparticles and Ni containing SiC nanoparticles. A Ni sulfamate electroplating bath containing the particles in suspension has been used and the deposition was carried out using both direct and pulse current at different frequencies. ASTM 387 gr.22 steel plates were used as substrate. The microstructure of the obtained deposits has been observed by Scanning Electron Microscope at both top surface and cross section after metallographic etching. The SiC content along the whole thickness of the deposits has been evaluated by Glow Discharge Optical Emission Spectroscopy. The corrosion resistance of the coatings has been evaluated by potentiodynamic polarization curves in two different corrosive environments: a solution containing 3.5% NaCI, and a solution containing H2S and NaCI at 50°C. The degradation mechanisms have been evaluated by SEM observation of the corroded samples on both top surface and cross section. The codeposition on SiC micro-particles decreased the protective properties of the coatings while the codeposition of nano-particles did not penalize the high corrosion resistance of the nickel coatings in the above mentioned corrosive environments. The microstructural modifications induced by the codeposition of the particles influence the degradation mechanisms
Corrosion behaviour of AA8xxx aluminium fins in heat exchangers
No full textDifferent alloys with composition in the range of AA8xxx series employed in the HVAC&R sector (heating, ventilating, air conditioning and refrigerating) were investigated in this work in order to evaluate the effect of alloy composition on the microstructure and corrosion resistance. The microstructure of the alloys was investigated by optical and scanning electron microscopy. The electrochemical behaviour was evaluated by means of electrochemical methods (open circuit potential and potentiodynamic measurements) and by immersion tests in aggressive electrolytes. The electrochemical behaviour observed for different alloy compositions in the 8xxx series evidenced that the corrosion resistance of alloys employed in the production of heat exchanger finstocks is strongly affected by small variations in the content of alloying elements, as well as by surface modifications due to the rolling process. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd
Steel Contamination of Biomedical Titanium Alloys during Hot Isostatic Pressing Treatments
No full textHot isostatic pressing (HIP) is an industrial treatment for the consolidation of metallic components. In the biomedical field, HIP processes are applied to titanium alloys fabricated by other sintering techniques to reduce residual porosity and improve the mechanical characteristics. Stainless steel sheet encased HIP processes are used when surface open porosities are present, in particular for powder metallurgy products or when nitrogen absorption is a major concern. In these circumstances, localized steel contamination may occur on the titanium surface. Contamination could be easily avoided using titanium encasing sheets, but these are rarely applied in industrial practice. In this work, Grade 2 and Grade 5 titanium have been treated with a standard HIP process. During treatment both alloys have been kept in contact with stainless steel casement, causing diffusion of elements inside the titanium. Samples have been investigated using two-dimensional profilometry and scanning electron microscopy. Qualitative and semi-quantitative compositional analyses have been performed using energy-dispersive x-ray spectroscopy and glow discharge optical emission spectrometry (GDOES). Microstructural analyses have been obtained after GDOES plasma etching in order to avoid any further surface preparation and easily obtain comparable results from the two different alloys. Localized potentiodynamic polarization curves were obtained on the different regions of the samples using microcell equipment. Both alloys were contaminated by stainless steel elements in the stained regions. A reduction in the corrosion resistance of the alloys has been observed due to the contamination. The experimental setting demonstrated the corrosion susceptibility of stainless steel contaminated biomedical titanium alloys after HIP, even if the passive behavior of titanium was not completely compromise
The Challenges and Advances in Recycling/Re-Using Powder for Metal 3D Printing: A Comprehensive Review
Full text linkThis review explores the critical role of powder quality in metal 3D printing and the importance of effective powder recycling strategies. It covers various metal 3D printing technologies, in particular Selective Laser Melting, Electron Beam Melting, Direct Energy Deposition, and Binder Jetting, and analyzes the impact of powder characteristics on the final part properties. This review highlights key challenges associated with powder recycling, including maintaining consistent particle size and shape, managing contamination, and mitigating degradation effects from repeated use, such as wear, fragmentation, and oxidation. Furthermore, it explores various recycling techniques, such as sieving, blending, plasma spheroidization, and powder conditioning, emphasizing their role in restoring powder quality and enabling reuse
Corrosion protection of AZ31 magnesium alloy by means of ZrO2 coatings deposited with sol-gel technique
No full textInfluence of oxidizing ability of the medium on the growth of lanthanide layers on galvanized steel
No full textProtection mechanisms offered to galvanized steel by lanthanide salts in a 0.1 M NaCl solution were
investigated by using electrochemical techniques such as polarization curves, electrochemical impedance
spectroscopy (EIS), scanning vibrating electrode technique (SVET) and surface analysis such as scanning
electron microscope (SEM) and glow discharge optical emission spectrometry (GDOES).
The role of the oxidizing ability of the medium was studied by changing the aeration conditions: aerated,
saturated, deaerated and acid deaerated solutions.
In aerated solution, the cerium deposition quickly offers an inhibition of the oxygen reduction. Current
density cartographies (SVET) are consistent with surface analysis and other electrochemical techniques.
2010 Elsevier Ltd. All rights reserve
Protezione dalla corrosione di leghe leggere con rivestimenti a base ZrO2 depositati con tecnica sol-gel
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The Use of the Electrochemical Micro-cell to Study Corrosion Inhibition by Cerium Species on AA1050 Aluminium Alloy
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