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.

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.

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 Calcination Ambiences on Phase Composition, Morphologies of Ceramic Coatings on Ti–6Al–4V Alloy by Micro-Arc Oxidation

2011 ◽  
Vol 412 ◽  
pp. 469-472
Author(s):  
Guo Dong Hao ◽  
Huan Yuan ◽  
Jing Zhang
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Phase Composition ◽  
Fluorescence Spectroscopy ◽  
Ceramic Coatings ◽  
X Ray ◽  
Micro Arc Oxidation ◽  
Oxidation Properties ◽  
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 NaAlO2solution. The coated samples were calcined in argon and air at 1000°C, 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°C to study the anti-oxidation properties of the samples. The results show that Al2TiO5had been decomposed in an hour and transformed intoα-Al2O3and rutile TiO2in air. However, Al2TiO5had been decomposed in four hours in argon and the final coating surface was completely composed ofα-Al2O3. The content of Al2O3was decreased from outside to inside layers and Ti2O3was 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 Calcination Ambiences on Phase Composition and High Temperature Oxidation Resistance Property of Ceramic Coatings on Ti–6Al–4V Alloy by Micro-Plasma Oxidation

2007 ◽  
Vol 336-338 ◽  
pp. 2481-2483 ◽  
Author(s):  
Guo Dong Hao ◽  
Zhao Hua Jiang ◽  
Zhong Ping Yao ◽  
Heng Ze Xian ◽  
Yan Li Jiang
Keyword(s):  
Phase Composition ◽  
High Temperature ◽  
Oxidation Resistance ◽  
High Temperature Oxidation ◽  
Ceramic Coatings ◽  
Plasma Oxidation ◽  
Temperature Oxidation ◽  
Complete Decomposition ◽  
Weight Gains ◽  
High Temperature Calcination

Compound ceramic coatings with the main crystalline of Al2TiO5 (as-coated samples) were prepared on Ti-6Al-4V alloy by pulsed bi-polar micro-plasma oxidation (MPO) in NaAlO2 solution. The coated samples were calcined in Ar and air at 1000oC, respectively. The phase composition, morphology and element content of the coatings were investigated by XRD, SEM and XRF. The samples treated in Ar and the as-coated ones were calcined in air at 1000oC to study the oxidation resistance of the samples. The results showed that Al2TiO5 decomposed and transformed into corundum and rutile TiO2 during the high temperature calcination. Al2TiO5 decomposed very quickly in air and the proportion of Al2O3 to TiO2 was 44:55 after a complete decomposition. On the contrary, Al2TiO5 decomposed very slowly in argon with the final proportion of Al2O3 to TiO2 of 81:18 on the coating surface. The morphology of the ceramic coatings after the calcination was also different. The coatings calcined in argon were fined: the grains and pores were smaller than those of the coatings calcined in air. The weight gains of both coatings changed in the form of parabola law, and the weight gains of the coated samples treated in argon were comparatively lower than that of the as-coated samples. During the high temperature calcination, the samples treated in argon cannot distort easily, compared with the as-coated ones.

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.

scholarly journals Morphology and Wear Resistance of Composite Coatings Formed on a TA2 Substrate Using Hot-Dip Aluminising and Micro-Arc Oxidation Technologies

Materials ◽  
2019 ◽  
Vol 12 (5) ◽  
pp. 799 ◽  
Author(s):  
Shaopeng Wang ◽  
Lian Zhou ◽  
Changjiu Li ◽  
Zhengxian Li ◽  
Hongzhan Li
Keyword(s):  
Wear Resistance ◽  
Surface Composition ◽  
Pure Titanium ◽  
Titanium Substrate ◽  
Ceramic Coatings ◽  
Oxide Ceramic ◽  
Pure Aluminium ◽  
X Ray ◽  
Micro Arc Oxidation

Aluminium layers were coated onto the surface of pure titanium using hot-dip aluminising technology, and then the aluminium layers were in situ oxidised to form oxide ceramic coatings, using the micro-arc oxidation (MAO) technique. The microstructure and composition distribution of the hot-dip aluminium coatings and ceramic layers were studied by using scanning electron microscopy and energy-dispersive X-ray spectroscopy. The phase structure of the MAO layers was studied using X-ray diffraction. The surface composition of the MAO layer was studied by X-ray photoelectron spectroscopy. The wear resistance of the pure titanium substrate and the ceramic layers coated on its surface were evaluated by using the ball-on-disc wear method. Therefore, aluminising coatings, which consist of a diffusion layer and a pure aluminium layer, could be formed on pure titanium substrates using the hot-dip aluminising method. The MAO method enabled the in-situ oxidation of hot-dip pure aluminium layers, which subsequently led to the formation of ceramic layers. Moreover, the wear resistance values of the ceramic layers were significantly higher than that of the pure titanium substrate.

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.

In situ x-ray study of the γ- to α-Al2O3 phase transformation during atmospheric pressure oxidation of NiAl(110)

2006 ◽  
Vol 21 (12) ◽  
pp. 3047-3057 ◽  
Author(s):  
A. Vlad ◽  
A. Stierle ◽  
N. Kasper ◽  
H. Dosch ◽  
M. Rühle
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Orientation Relationship ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Oxidation In Air ◽  
Α Al2o3 ◽  
Underlying Substrate

The oxidation in air of NiAl(110) was investigated in the temperature range from 870 °C–1200 °C by in situ x-ray diffraction and transmission electron microscopy. Oxidation at 870 °C and 1 bar oxygen leads to the formation of an epitaxial layer of γ-alumina showing an R30° orientation relationship with respect to the underlying substrate. At oxidation temperatures between 950 °C and 1025 °C, we observed a coexistence of epitaxial γ- and polycrystalline δ-Al2O3. The α-Al2O3 starts to form at 1025 °C and the complete transformation of metastable phases to the stable α-alumina phase takes place at 1100 °C. The fcc-hcp martensitic-like transformation of the initial γ-Al2O3 to epitaxial α-Al2O3 was observed. X-ray diffraction and cross-section transmission electron microscopy proved the existence of a continuous epitaxial α-Al2O3 layer between the substrate and the polycrystalline oxide scale, having a thickness of about 150 nm. The relative orientation relationship between the epitaxial alumina and the underlying substrate was found to be NiAl(110) || α-Al2O3 (0001) and [110] NiAl || [1120].

An Advanced Technique for High Temperature X-Ray Elastic Constant and Stress Investigations

1992 ◽  
Vol 36 ◽  
pp. 411-422
Author(s):  
Chun Liu ◽  
Jean-Lou Lebrun ◽  
François Sibieude
Keyword(s):  
High Temperature ◽  
Elastic Constant ◽  
High Temperature Oxidation ◽  
Differential Method ◽  
Stress Evolution ◽  
Advanced Technique ◽  
Temperature Oxidation ◽  
X Ray ◽  
Refractory Alloys

AbstractA high temperature in situ X-Tay diffraction (HTXRD) instrument was devised for residual stress (RS) and X-ray elastic constant (XECs) investigations. The aim was to gain a better understanding of the stresses developed during high temperature oxidation, which is essential for the lifetime improvement of refractory alloys. The investigators use sin2ψ method to survey the stress evolution during oxidation in both the scale and the substrate, and differential method to determine the XECs that relate the measured/measurable deformation to the stress state of the materials studied. The stresses on the Ni/NiO system are measured in situ. The XECs are determined on XC75 steel samples. This paper presents the theories of stresses and XECs determined by HTXRD and briefly discusses the experimental results.

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