| LI Xi-jin,XUE Wen-bin.Effect of Aluminate Electrolyte on Growth and Properties of Micro-arc Oxidation Coating on TiAl Alloy[J],48(7):97-103 |
| Effect of Aluminate Electrolyte on Growth and Properties of Micro-arc Oxidation Coating on TiAl Alloy |
| Received:March 29, 2019 Revised:July 20, 2019 |
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| DOI：10.16490/j.cnki.issn.1001-3660.2019.07.010 |
| KeyWord:TiAl alloy micro-arc oxidation plasma electrolysis oxidation aluminate electrolyte structure, hardness |
| Author | Institution |
| LI Xi-jin |
1.School of Physics and Electronics, Henan University, Kaifeng , China |
| XUE Wen-bin |
2.School of Nuclear Science and Technology, Beijing Normal University, Beijing , China |
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| Abstract: |
| The work aims to improve the surface structure and mechanical properties of TiAl alloy. Micro-arc oxidation (MAO) method was used to fabricate ceramic coating on TiAl alloy in NaAlO2 electrolyte. The growth properties of coating were analyzed at different stages during MAO, and the effect of aluminate solution on the growth rate of MAO coating was studied. Micro-hardness test and micro-scratch test were used to evaluate the effect of coating on substrate hardness and the change in binding force of coating/substrate. The structure of the coating with different thickness was studied by scanning electron microscope (SEM), and elements distribution in the coating was analyzed by Energy-dispersive X-ray spectroscopy (EDS). The energy dispersive X-ray detector (XRD) was adopted to investigate the change in the phase structure of coatings. The thickness of the coating increased with the prolongation of MAO time in aluminate solution, and finally reached 57 μm. MAO process was divided into two stages, namely the initial bright-spark stage with a growth rate of 1 μm/min, and the followed dark-spark stage with a growth rate of 0.23 μm/min. The coating included two distinct layers, namely the condensed inner layer and the loose outer layer. The condensed layer had fewer pores and lower concentration of Al and Ti, while the outer layer had larger porosity and higher content of Al and lower content of Ti. From SEM results, the inner layer was bound to the substrate well. The binding force of coating/substrate was about 45 N when measured by the micro-scratch test. The phase components of the coatings were Rutile-TiO2 and Al2TiO5, and the ratio Al2TiO5/Rutile-TiO2 of increased with the increase of coating thickness. The micro-hardness of MAO coating increased with the increase of coating thickness, and a hardness of 1450HV was measured on the coating after 120 min, which was more than three times of that on substrate. 55 μm ceramic coating can be prepared through MAO on TiAl alloy in NaAlO2. The coating has excellent binding force to the substrate, which can improve the surface structure of substrate, improve the hardness of materials and increase the wear resistance. |
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