EFFECTS OF α-Al2O3 NANOADDITIVE ON THE PROPERTIES OF CERAMIC COATINGS PREPARED IN BORATE ELECTROLYTE BY MICRO-ARC OXIDATION

2012 ◽  
Vol 19 (04) ◽  
pp. 1250038 ◽  
Author(s):  
H. X. LI ◽  
H. H. ZHU ◽  
X. WU ◽  
Z. G. JI
Keyword(s):  
Phase Composition ◽  
Great Influence ◽  
Ceramic Coatings ◽  
Micro Hardness ◽  
X Ray Diffraction ◽  
Micro Arc Oxidation ◽  
Edx Analyses ◽  
6063 Aluminum Alloy ◽  
Α Al2o3 ◽  
Wear Tests

Ceramic coatings have been synthesized on 6063 aluminum alloy by micro-arc oxidation (MAO) technique in the solution of Na2B4O7 electrolyte with and without α- Al2O3 nanoadditive. Effects of α- Al2O3 nanoadditive on the phase composition, micro-structure, micro-hardness, adhesion and wear resistance of the prepared ceramic coatings have been investigated in this paper. The phase composition and microstructure of the MAO coatings were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDX) analyses, respectively. Micro-hardness, adhesion and tribological and wear tests were also performed. The results showed that the α- Al2O3 nanoadditive doped in the electrolyte had great influence on the structural and mechanical properties of the ceramic coatings.

Influences of Calcination Ambiences on Morphologies, Phase Composition and Contents of the Elements of Ceramic Coatings on Ti Alloy by Micro-Arc Oxidation

2012 ◽  
Vol 512-515 ◽  
pp. 1066-1069
Author(s):  
Jin Xue Zhang
Keyword(s):  
Electron Microscopy ◽  
Phase Composition ◽  
Ceramic Coatings ◽  
Ti Alloy ◽  
X Ray ◽  
Micro Arc Oxidation ◽  
Oxidation Properties ◽  
Α Al2o3 ◽  
Scanning Electron

Compound ceramic coatings with the main crystal phase of Al2TiO5 (as-coated samples) were prepared in situ on the surface of Ti-6Al-4V alloy by means of pulsed bi-polar micro-arc oxidation (MAO) in an NaAlO2 solution. The coated samples were calcined in argon and air at 1000 oC, respectively. The phase composition, surface and section morphology, and element contents of the ceramic coatings were investigated by X-ray diffractometry (XRD), Scanning electron microscopy (SEM) and X-ray fluorescence spectroscopy (XRF). The samples were treated in argon and the as-coated ones were calcined in air at 1000 oC to study the anti-oxidation properties of the samples. The results show that Al2TiO5 had been decomposed in an hour and transformed into α-Al2O3 and rutile TiO2 in air. However, Al2TiO5 had been decomposed in four hours in argon and the final coating surface was completely composed of α-Al2O3. The content of Al2O3 was decreased from outside to inside layers and Ti2O3 was formed in the coating. Furthermore, the morphology of the ceramic coatings after the calcination was different. The coatings calcined in argon were finer; the grains and pores were smaller than those in air.

Influences of Different Calcinations Ambience on Phase Composition and Morphologies of Ceramic Coatings on Ti Alloy by Micro-Arc Oxidation

2010 ◽  
Vol 97-101 ◽  
pp. 1554-1557
Author(s):  
Guo Dong Hao ◽  
Nai Wu Zhang ◽  
Tao Yun ◽  
Jin Wang ◽  
Bo Lian ◽  
...  
Keyword(s):  
Phase Composition ◽  
High Temperature Oxidation ◽  
Ceramic Coatings ◽  
Ti Alloy ◽  
Temperature Oxidation ◽  
Weight Gains ◽  
Micro Arc Oxidation ◽  
Oxidation Properties ◽  
Α Al2o3

Compound ceramic coatings with the main crystalline of Al2TiO5 (as-coated samples) were prepared in situ on the surface Ti-6Al-4V alloy by means of pulsed bi-polar micro-arc oxidation (MAO) in a NaAlO2 solution. The coated samples were calcined in argon and air at 1000 oC, respectively. The phase composition, surface morphology of the ceramic coatings were investigated by XRD, SEM and XRF. The samples were treated in argon and the as-coated ones were calcined in air at 1000 oC to study the anti-oxidation properties of the samples. The results show that Al2TiO5 was decomposed very soon and transformed into α-Al2O3 and rutile TiO2 in air. However, Al2TiO5 was decomposed very slowly in argon and the final coating surface was completely α-Al2O3. Also, the morphology of the ceramic coatings after the calcination was different. The coatings calcined in argon were fined; grains and pores were smaller than those in air. High temperature oxidation occurred very strongly in the TC4 substrate, the weight gains of the as-coated ceramic coatings and the treated ones in argon were nearly changing in the form of parabola, and the weight gains of the coated samples treated in argon were comparatively lower than those of the as-coated samples.

scholarly journals Microstructure and Wear Properties of Micro Arc Oxidation Ceramic Coatings

Materials ◽  
2020 ◽  
Vol 13 (4) ◽  
pp. 970 ◽  
Author(s):  
Xiaoben Qi ◽  
Hailong Shang ◽  
Bingyang Ma ◽  
Rulin Zhang ◽  
Leyang Guo ◽  
...  
Keyword(s):  
Interaction Effect ◽  
Failure Modes ◽  
Ceramic Coatings ◽  
Element Distribution ◽  
X Ray Diffraction ◽  
Electrical Parameters ◽  
Wear Properties ◽  
Spalling Failure ◽  
Micro Arc Oxidation ◽  
Α Al2o3

The interaction effect of micro arc oxidation (MAO) parameters on the microstructure and wear properties was investigated. The results showed that the electric current and oxidation time significantly influenced the thickness and grinding crack width of the ceramic coatings within the range of the selected parameters, and the interaction effect of the electrical parameters was not obvious. The surface morphology, cross-section morphology, and element distribution of the coatings were observed using scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). The results showed that ceramic coatings with γ-Al2O3 and α-Al2O3 formed, which enhanced the coating performance. After that, the microhardness and wear resistance were tested. Under the optimal process, the microhardness of a coating section was up to 1200 HV0.1, and the friction coefficient was just 0.3. When wear occurred, the volcanic microstructures experienced extrusion and deformation, and then peeled off under shear stress, which led to the formation of a grinding crack. The main failure modes of the micro arc oxidation coatings were abrasive wear and spalling failure.

Influences of Argon Ambience on Phase Composition and High Temperature Oxidation Resistance Property of Ceramic Coatings on Ti Alloy by Micro-Arc Oxidation

2012 ◽  
Vol 512-515 ◽  
pp. 1078-1081
Author(s):  
Guo Dong Hao ◽  
Zhi Gang Yang ◽  
Xu Xu Zheng ◽  
Xu Zhao Zeng ◽  
Xu Yan Wu
Keyword(s):  
Phase Composition ◽  
Ceramic Coatings ◽  
Temperature Oxidation ◽  
X Ray ◽  
High Oxidation ◽  
Weight Gains ◽  
Micro Arc Oxidation ◽  
Oxidation Properties ◽  
Α Al2o3

Abstract. Compound ceramic coatings with the main crystal phase of Al2TiO5 (as-coated samples) were prepared in situ on the surface of Ti-6Al-4V alloy by means of pulsed bi-polar micro-arc oxidation (MAO) in an NaAlO2 solution. The coated samples were calcined in argon and air at 1000 oC, respectively. The phase composition, surface and section morphology, and element contents of the ceramic coatings were investigated by X-ray diffractometry(XRD), Scanning electron microscopy (SEM) and X-ray fluorescence spectroscopy (XRF). The samples were treated in argon and the as-coated ones were calcined in air at 1000 oC to study the anti-oxidation properties of the samples. The results show that Al2TiO5 had been decomposed in an hour and transformed into α-Al2O3 and rutile TiO2 in air. However, Al2TiO5 had been decomposed in four hours in argon and the final coating surface was completely composed of α-Al2O3. The content of Al2O3 was decreased from outside to inside layers and Ti2O3 was formed in the coating. Furthermore, the morphology of the ceramic coatings after the calcination was different. The coatings calcined in argon were finer; the grains and pores were smaller than those in air. The high oxidation reaction of the TC4 substrate was the fiercest and the weight gains of the coated samples treated in argon was the lowest. The weight gains of the ceramic coatings were nearly changing in the form of parabola law.

Research on Properties and Formation Mechanism of Ceramic Coatings Prepared by Micro-Arc Oxidation on 2024 Aluminum Alloy Surface

2006 ◽  
Vol 315-316 ◽  
pp. 259-263 ◽  
Author(s):  
Wan Sheng Zhao ◽  
T.Z. Xin ◽  
Zhen Long Wang ◽  
J.C. Liu
Keyword(s):  
Phase Composition ◽  
Ceramic Coatings ◽  
High Energy ◽  
High Energy Density ◽  
Alloy Surface ◽  
Al Alloy ◽  
X Ray Diffraction ◽  
2024 Aluminum Alloy ◽  
Micro Arc Oxidation ◽  
Coating Formation

In this paper, ceramic coatings prepared on 2024 Al alloy surface in electrolyte by micro-arc oxidation are studied. The parameter of discharge and rate of ceramic coating formation are investigated. We analyzed microstructure and phase composition of the coatings by scanning electronic microscopy (SEM) and X-ray diffraction (XRD), and studied the tribological performance of the coatings. The reactions on the electrode surface are deduced and the mechanism of coating formation has been analyzed. The results show that the relation between the thickness and reaction time is not linear. The ceramic coatings contain phase γ-Al2O3 andα-Al2O3; there is a big difference in contents of phase composition between inner coating and outer coating due to the different cooling rates of them. In MAO process, the coating undergoes a course of melting, solidifying and cooling. The coating can be divided into three layers, namely, transition layer, compact layer, and loose layer. The coating and substrate adheres firmly by a metallurgical process. Not only the elements of electrolyte (K, Si) and substrate (Cu) are found in the coatings but also the element of cathode (Fe). The Si-Al-O complex compound is formed in the discharge channels under high energy density condition.

Structure and Mechanical Properties of Ceramic Coatings Fabricated by Micro-Arc Oxidation

2008 ◽  
Vol 47-50 ◽  
pp. 554-557 ◽  
Author(s):  
Hong Xia Li ◽  
Ren Guo Song ◽  
J. Zhao
Keyword(s):  
High Hardness ◽  
Hardness Test ◽  
Ceramic Coatings ◽  
Elemental Distribution ◽  
Surface Adhesion ◽  
Micro Hardness ◽  
Al2o3 Ceramic ◽  
Micro Arc Oxidation ◽  
Excellent Adhesion ◽  
Α Al2o3

Al2O3 ceramic coatings were directly prepared on 6063 aluminum alloy in borate electrolytes by micro-arc oxidation (MAO) technique. The phase composition, microstructure, elemental distribution, and micro-hardness of Al2O3 ceramic coatings were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), and micro-hardness test. XRD results show that the coating consists of α-Al2O3 and γ-Al2O3. SEM results show that the pores with different sizes distributed all over the coating surface. Adhesion and tribological and wear tests were also performed. It was found that ceramic coatings with high hardness, excellent adhesion and wear resistance could be formed.

scholarly journals Phase composition of coatings on the D16 alloy during micro-arc oxdation in alkaline and silicate electrolytes

2020 ◽  
Vol 1,2020 (1,2020 (124)) ◽  
pp. 51-55
Author(s):  
Subbotina V ◽  
Belozerov V ◽  
Sobol’ O
Keyword(s):  
Phase Composition ◽  
Liquid Glass ◽  
Amorphous State ◽  
Practical Significance ◽  
Alkaline Electrolyte ◽  
X Ray ◽  
Micro Arc Oxidation ◽  
Coating Formation ◽  
Al2o3 Phase ◽  
Α Al2o3

Goal. The influence of electrolysis conditions at different electrolyte compositions on the phase formation of coatings obtained by micro-arc oxidation (MDO) on an aluminum alloy D16 was studied. Method. For electrolysis, two types of electrolytes were used: alkaline electrolyte (solution (KOH) in distilled water), silicate electrolyte (with different percentages of Na2SiO3 component). Research results. It was found that the phase composition of the MAO coatings obtained in an alkaline (KOH) electrolyte mainly consists of γ - Al2O3 phases and, to a much lesser extent, the α-Al2O3 phases. An increase in the KOH concentration leads to a shift in the γ – Al2O3 → α – Al2O3 polymorphic reaction toward the formation of the hardest α-Al2O3 phase (corundum). The formation of the preferred orientation of the growth of crystallites of γ – Al2O3 and α – Al2O3 phases during their formation in an alkaline electrolyte was not detected. Scientific novelty. A significant influence on the mechanism and processes of coating formation is made by the addition of liquid glass (Na2SiO3) in the electrolyte. In this case, the growth rate of the coating increases significantly, but the size of the ordering regions decreases from crystalline to X-ray amorphous. The phase composition of the MAO coatings, when they are formed in a silicate electrolyte, varies from a mixture of the γ - Al2O3 phase and mullite (3Al2O3 • 2SiO2) with a low content of liquid glass (10 g/l Na2SiO3) to the formation of only the X-ray amorphous phase with a high content of liquid glass in the electrolyte (50 g/l Na2SiO3). Practical significance. It was concluded that the use of an alkaline or silicate electrolyte with different percentages allows a wide variation of both the phase composition and structural state (α- Al2O3 and γ- Al2O3 phases, mullite (3Al2O3 • 2SiO2) or X-ray amorphous state) and the kinetics of growth the coating itself.

Effects of Cr on Microstructure and Hardness of HVOF-Sprayed WC-Co Coating

2011 ◽  
Vol 317-319 ◽  
pp. 301-306 ◽  
Author(s):  
Li Jun Wang ◽  
Hui Chen ◽  
Yan Liu ◽  
Guo Qing Gou ◽  
Da Li
Keyword(s):  
Phase Composition ◽  
Spray Coating ◽  
Thermal Spray Coating ◽  
Micro Hardness ◽  
X Ray Diffraction ◽  
Wear And Corrosion ◽  
Application Potential ◽  
Confocal Scanning ◽  
Wear And Corrosion Resistance ◽  
New Phase

In the areas of remanufacturing and working conditions with requirements of wear and corrosion resistance, the WC-Co thermal spray coating has a wide applications. WC-10Co-4Cr is an excellent, has great application potential as a coating composition. In this research, the two kinds of coatings, WC-12Co and WC-10Co-4Cr, were sprayed by high velocity oxygen-flame(HVOF). The phase composition is studied by X-ray diffraction(XRD). The porosity is investigated by lase confocal scanning microscope(LCSM), and the micro-hardness is measured. The results show that, The porosity of two coatings don't differ, this maybe has relation with the parameters in the spraying process.The micro-hardness of WC-10Co-4Cr coating is higher than that of WC-12Co coating. Compared with the phase composition of WC-12Co coating, there are new phase composition Cr7C3, Cr23C6 and Cr2WO6 in the WC-10Co-4Cr coating. And the content of W2C and η phase are reduced in WC-10Co-4Cr coating. Cr had no effect on the lattice transformation of cobalt.

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