Micro Arc Oxidation of AZ91 Mg Alloy for Improved Corrosion Resistance

2011 ◽  
Vol 312-315 ◽  
pp. 877-881 ◽  
Author(s):  
H.G. Yavuz ◽  
M. Gunyuz ◽  
Isa Metin Ozkara ◽  
Murat Baydogan ◽  
Huseyin Cimenoglu
Keyword(s):  
Corrosion Resistance ◽  
Surface Topography ◽  
Xrd Analysis ◽  
Processing Parameters ◽  
Mg Alloy ◽  
X Ray Diffraction ◽  
Corrosive Solution ◽  
Weight Losses ◽  
Before And After ◽  
Micro Arc Oxidation

AZ91 Mg alloy was subjected to the micro arc oxidation process by using different processing parameters. Following oxidation, surface topography and qualitative phase analysis were made by tabletop digital microscopy and X-ray diffraction (XRD) analysis. In order to evaluate the relative corrosion resistance of the samples that were oxidized in different parameters, the samples were immersed in a corrosive solution for 6 days and the weight losses before and after the corrosion tests were compared. Relative corrosion resistance of the samples was evaluated on the basis of surface topography.

scholarly journals Investigations on Water Jet Peening of AZ31B Mg Alloy for Bio Medical Implants

2021 ◽  
Author(s):  
Mugilvalavan Mohan ◽  
Muruganandhan Radhakrishnan ◽  
Yuvaraj Natarajan
Keyword(s):  
Surface Roughness ◽  
Corrosion Resistance ◽  
Surface Topography ◽  
Optimization Technique ◽  
Traverse Speed ◽  
Xrd Analysis ◽  
Water Jet ◽  
Mg Alloy ◽  
Working Process ◽  
Electrochemical Test

Abstract Among different unconventional peening technique, water jet is cold working process has capable to produce surface topography on wide variety of materials. This paper deals with the effect of water jet peening on the corrosion resistance and the surface topography of AZ31B Mg alloy. Variations in water jet peening variables including standoff distance, traverse speed and multiple passes have been employed in this study. A study of the enhancement in hardening and roughening effect was made following the peening process. 29.44% Improvements in microhardness and 31.06% reduction in surface roughness were observed on the peened surfaces. Optimal peened surface was obtained through use of the multi-objective optimization technique, namely, TOPSIS, which utilizes response variables such as micro hardness and surface roughness. In this study, Surface Topography, XRD Analysis and Electrochemical test were conducted. In addition, analysis of the Microstructure of corroded region was made in the unpeened and optimized peened surfaces. Surface topography parameters including Sa, Sq, SSk, Sku results confirmed the suitability of the peened surface for ooseointegration and cell growth. FWHM value measured from XRD peaks showed the formation of grain refinement on the peened surface, and the results showed promising improvements in the corrosion resistance compared to the unpeened AZ31B Mg alloy.

Effects of Interaction of (NaPO3)6 and NaH2PO4 on Ca/P of MAO Bio-Ceramic Coating of ZK60 Mg Alloy

2013 ◽  
Vol 745-746 ◽  
pp. 21-27
Author(s):  
Cui Ling Du ◽  
Jing Chen ◽  
Bin Bin Cao ◽  
Lei Xu ◽  
Sheng Lu
Keyword(s):  
Corrosion Resistance ◽  
Ceramic Coating ◽  
Energy Dispersive Spectrometer ◽  
Mg Alloy ◽  
Molar Ratio ◽  
X Ray Diffraction ◽  
Orthogonal Experiments ◽  
Micro Arc Oxidation ◽  
Evolution Phase

Micro-arc oxidation (MAO) process was conducted on ZK60 Mg alloy in a basic biologic electrolyte composed of silicate by addition of (NaPO3)6 and NaH2PO4. The microstructural evolution, phase composition and in vitro corrosion resistance of the coating were investigated by means of scanning electron microscopy (SEM) coupled with an energy dispersive spectrometer (EDS) and X-ray diffraction (XRD). The results revealed that bioactive elements Mg, Ca, P and Si were remained in the bio-ceramic coating which can be prepared in suitable biologic electrolyte. For the interaction of (NaPO3)6 and NaH2PO4 , the Ca/P molar ratio of the coating in the optimized biologic electrolyte reached to 1.24 by L9 (34) orthogonal experiments. Compared with the bare ZK60 Mg alloy, the corrosion resistance of the optimized sample in 37 Ringers solution was improved by 4 orders.

Effect of Processing Parameters on the Structural and Mechanical Properties of Micro Arc Oxidized Aluminium Alloy

2010 ◽  
Vol 297-301 ◽  
pp. 942-947
Author(s):  
Isa Metin Ozkara ◽  
Murat Baydogan
Keyword(s):  
Corrosion Resistance ◽  
Aluminium Alloy ◽  
Xrd Analysis ◽  
Processing Parameters ◽  
Morphological Characterization ◽  
Cross Sectional ◽  
Wear And Corrosion ◽  
Thickness Gage ◽  
Micro Arc Oxidation ◽  
Wear And Corrosion Resistance

The micro arc oxidation process (MAO) was applied to a 2024 ingot aluminium alloy by an AC MAO equipment using an alkali based electrolyte. The processing parameters of the process were positive and negative voltage pulse durations. Structural and morphological characterization of the coating were made by a scanning electron microscope (SEM), an X-ray diffractometer (XRD), a surface profilometer and a thickness gage operating according to the Eddy current principle. Cross sectional hardness of the coatings was measured, and reciprocating wear and immersion corrosion tests were performed. XRD analysis showed that an oxide layer comprising - and -Al2O3 phases was produced on the surface, whose thickness and surface roughness varied by the processing parameters applied. Wear and corrosion resistance of the original alloy significantly improved upon the MAO process. Variation of hardness, wear and corrosion resistance with respect to the processing parameters was discussed based on the experimental data obtained.

Properties of Anodic Coatings Obtained in an Organic, Environmental Electrolyte by Micro Arc Oxidation on Magnesium Alloy

2011 ◽  
Vol 189-193 ◽  
pp. 1001-1004
Author(s):  
Rong Fa Zhang ◽  
Shu Fang Zhang ◽  
Jian Chao Gong ◽  
Wen Long Liu ◽  
He Jing Zhou ◽  
...  
Keyword(s):  
Corrosion Resistance ◽  
Magnesium Alloy ◽  
Phytic Acid ◽  
Immersion Test ◽  
X Ray Diffraction ◽  
X Ray ◽  
Before And After ◽  
Micro Arc Oxidation ◽  
Coating Formation ◽  
Edx Analyses

In a solution containing 10g/L NaOH and 12g/L phytic acid, anodic coatings were obtained by micro arc oxidation (MAO) on AZ91HP magnesium alloy. The morphology, structure and composition of anodic coatings were investigated by scanning electron microscope (SEM), X-ray diffraction (XRD) and energy dispersive X-ray (EDX). The corrosion resistance of magnesium alloy before and after MAO treatment was evaluated by immersion test and potentiodynamic polarization testing in 3.5wt. % NaCl solution. The coatings were evenly formed on the substrate and mainly composed of MgO. EDX analyses showed that phytic acid took part in the coating formation. Compared with the substrate, the corrosion resistance of magnesium alloy after MAO treatment was improved considerably.

scholarly journals Effect of Molybdenum Content on the Corrosion and Microstructure of Low-Ni, Co-Free Maraging Steels

Metals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 852
Author(s):  
Asiful H. Seikh ◽  
Hossam Halfa ◽  
Mahmoud S. Soliman
Keyword(s):  
Corrosion Resistance ◽  
Electrochemical Impedance ◽  
Microstructural Analysis ◽  
Xrd Analysis ◽  
X Ray Diffraction ◽  
Alloying Element ◽  
X Ray ◽  
Maraging Steels ◽  
Eds Analysis ◽  
Electroslag Refining

Molybdenum (Mo) is an important alloying element in maraging steels. In this study, we altered the Mo concentration during the production of four cobalt-free maraging steels using an electroslag refining process. The microstructure of the four forged maraging steels was evaluated to examine phase contents by optical microscopy, scanning electron microscopy (SEM), and X-ray diffraction (XRD) analysis. Additionally, we assessed the corrosion resistance of the newly developed alloys in 3.5% NaCl solution and 1 M H2SO4 solution through potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. Furthermore, we performed SEM and energy-dispersive spectroscopy (EDS) analysis after corrosion to assess changes in microstructure and Raman spectroscopy to identify the presence of phases on the electrode surface. The microstructural analysis shows that the formation of retained austenite increases with increasing Mo concentrations. It is found from corrosion study that increasing Mo concentration up to 4.6% increased the corrosion resistance of the steel. However, further increase in Mo concentration reduces the corrosion resistance.

Effect of pH of coating solution on the adhesion strength and corrosion resistance of hydroxyapatite and octacalcium phosphate coated WE43 alloy

2021 ◽  
pp. 088532822110125
Author(s):  
Tuyet Thi Anh Ngo ◽  
Sachiko Hiromoto ◽  
Linh Chi Do ◽  
Hanh Hong Pham ◽  
Le Hanh
Keyword(s):  
Corrosion Resistance ◽  
Adhesion Strength ◽  
Corrosion Current ◽  
Xrd Analysis ◽  
Octacalcium Phosphate ◽  
Solution Deposition ◽  
Chemical Solution Deposition Method ◽  
Before And After ◽  
Coating Layers ◽  
We43 Alloy

Hydroxyapatite (HAp) and octacalcium phosphate (OCP) layers were formed on Mg- 4mass% Y- 3mass% rare earth (WE43) alloy by a chemical solution deposition method at various pH values of pH 5.5, 6.2, 7.5, and 8.6. Adhesion strength of HAp and OCP layers was evaluated before and after immersing in a medium for 14 days by a pull-off test. The corrosion resistance of these coatings was measured by polarization tests performed in a simulated body fluid (SBF). XRD analysis demonstrated that HAp coating layers were formed at pH 7.5 and 8.6, while OCP coating layers were formed at pH 5.5 and 6.2. Adhesion test results showed that the as-coated pH7.5-HAp layer had the highest adhesion strength of 8.6 MPa, which was attributed to the very dense structure of the coating layer. The as-coated pH8.6-HAp layer showed the adhesion strength of 6.5 MPa. The adhesion strength of the as-coated pH5.5- and pH6.2-OCP layers was 3.9 and 7.1 MPa, respectively, that was governed by the thick and fragile property of the layers. After immersing in the medium for 14 days, the adhesion strength of pH7.5- and pH8.6-specimens decreased to 5.8 and 5.6 MPa, respectively. The pitting corrosion and formation of Mg(OH)2 under the HAp layers were responsible for the decrease of adhesion strength. The polarization tests in SBF at 37 °C showed that the corrosion current density decreased with the HAp and OCP coatings, indicating the improvement of the corrosion resistance of WE43 alloy. The HAp coatings improved the corrosion resistance more efficiently than the OCP coatings.

scholarly journals Ostrich eggshell as calcium source for the synthesis of hydroxyapatite and hydroxyapatite partially substituted with zinc

Cerâmica ◽  
2016 ◽  
Vol 62 (364) ◽  
pp. 386-391 ◽  
Author(s):  
J. R. M. Ferreira ◽  
L. H. L. Louro ◽  
A. M. Costa ◽  
J. B. de Campos ◽  
M. H. Prado da Silva
Keyword(s):  
Xrd Analysis ◽  
Quantitative Chemical Analysis ◽  
X Ray Diffraction ◽  
Spectroscopy Technique ◽  
X Ray ◽  
Heat Treated ◽  
Before And After ◽  
Calcium Source ◽  
The Fourier Transform ◽  
Ostrich Eggshell

Abstract In the present study, hydroxyapatite and Zn-substituted hydroxyapatite powders were synthesized using ostrich eggshell as a calcium source. The samples were analyzed by scanning electron microscopy with field emission gun, and X-ray diffraction (XRD) to identify the present phases, and X-ray fluorescence spectroscopy for quantitative chemical analysis of the synthesized and heat treated powders. The Fourier transform infrared spectroscopy technique was used before and after heat treatments at 700, 900 and 1100 °C in order to identify the functional groups present, as an additional technique to the XRD analysis. The results presented in this study represent a promising method for synthesis of hydroxyapatite and hydroxyapatite partially substituted with zinc, since the results showed no undesirable phases or impurities in the produced powders. It was observed that Zn-substituted hydroxyapatite showed higher thermal stability, when compared to pure hydroxyapatite.

scholarly journals Formation and Corrosion Resistance of Micro-Arc Oxidation Coating on Equal-Channel Angular Pressed AZ91D Mg Alloy

Metals ◽  
2016 ◽  
Vol 6 (12) ◽  
pp. 308 ◽  
Author(s):  
Aibin Ma ◽  
Fumin Lu ◽  
Qi Zhou ◽  
Jinghua Jiang ◽  
Dan Song ◽  
...  
Keyword(s):  
Corrosion Resistance ◽  
Mg Alloy ◽  
Micro Arc Oxidation

scholarly journals Corrosion properties of Zn-Ni-P alloys in neutral model medium

2014 ◽  
Vol 12 (11) ◽  
pp. 1183-1193 ◽  
Author(s):  
Vassil Bachvarov ◽  
Miglena Peshova ◽  
Stefana Vitkova ◽  
Nikolai Boshkov
Keyword(s):  
Corrosion Resistance ◽  
Xrd Analysis ◽  
Ternary Alloys ◽  
X Ray Diffraction ◽  
Model Medium ◽  
Experimental Conditions ◽  
Corrosion Properties ◽  
X Ray ◽  
Protective Ability ◽  
Corrosion Medium

AbstractThe presented work reports on the peculiarities of the anodic behavior, corrosion resistance and protective ability of electrodeposited Zn-Ni-P alloys with a different composition in a model corrosion medium of 5% NaCl. Three characteristic coating types have been investigated using experimental methods such as potentiodynamic polarization (PD) technique and polarization resistance (Rp) measurements. In addition, X-ray diffraction (XRD) analysis as well as scanning electron microscopy (SEM) coupled with an Energy-dispersive X-ray (EDAX) device were applied to determine the differences in the chemical composition and surface morphology which appeared as a result of the corrosion treatment. The data obtained are compared to those of electrodeposited pure Zn coatings with identical experimental conditions demonstrating the enhanced protective characteristics of the ternary alloys during the test period in the model medium. The influence of the chemical and phase composition of the alloys on its corrosion resistance and protective ability is also commented and discussed.

Improving Corrosion Resistance of AA2014 Welds with Micro Arc Oxidation

2013 ◽  
Vol 765 ◽  
pp. 634-638 ◽  
Author(s):  
Roshan Jacob ◽  
S.A. Srinivasan ◽  
K. Sivaprasad ◽  
V. Muthupandi
Keyword(s):  
Corrosion Resistance ◽  
Current Mode ◽  
Silicate Solution ◽  
The Other ◽  
X Ray Diffraction ◽  
Gas Tungsten Arc ◽  
Weld Metals ◽  
Full Penetration ◽  
Gtaw Process ◽  
Micro Arc Oxidation

Autogenous single pass full penetration welds of 2.8 mm thick AA 2014 plates were produced by un-pulsed and pulsed gas tungsten arc welding (GTAW) process. In pulsed current mode, two levels of pulsing viz., 3 and 6 Hz were employed. In order to improve the corrosion resistance of weld metals, micro arc oxidation (MAO) treatment was given in aqueous silicate solution containing either borax or tungstate. The MAO treatment was carried out for 10, 20 and 30 minutes. Irrespective of the electrolyte composition, surface roughness increased with increasing treatment duration. However, the effect was observed to be significant with borax addition. X-ray diffraction studies showed that γ-Al2O3 content in the coating continued to increase up to 20 minutes and for the coating produced with 30 minutes duration the α-Al2O3 content was found to be more than γ-Al2O3. The coating treated for 30 minutes exhibited relatively poorer corrosion resistance than the other coated specimens. The better corrosion resistance offered by the coating obtained after 20 minutes, compared with the other coatings, could be attributed to the nature of the oxide and its content. Even though tungstate addition improved hardness of the coating, borax addition was found to enhance the corrosion resistance.

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