Effect of Na<sub>2</sub>WO<sub>4</sub> in Electrolyte on Microstructure and Tribological Behavior of Micro-arc Oxidation Coatings on Ti<sub>2</sub>AlNb Alloy
Micro-arc oxidation (MAO) ceramic coatings were prepared on Ti<sub>2</sub>AlNb alloy in silicate/phosphate electrolytes with different concentrations of Na<sub>2</sub>WO<sub>4</sub>. The influence of Na<sub>2</sub>WO<sub>4</sub> on the coat...
| Main Authors: | , , , , , |
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| Format: | Article |
| Language: | zho |
| Published: |
Journal of Materials Engineering
2018-02-01
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| Series: | Cailiao gongcheng |
| Subjects: | |
| Online Access: | http://jme.biam.ac.cn/CN/Y2018/V46/I2/84 |
| Summary: | Micro-arc oxidation (MAO) ceramic coatings were prepared on Ti<sub>2</sub>AlNb alloy in silicate/phosphate electrolytes with different concentrations of Na<sub>2</sub>WO<sub>4</sub>. The influence of Na<sub>2</sub>WO<sub>4</sub> on the coating growth process, coating structure and composition was analyzed by SEM, XRD and XPS. The tribological behavior of MAO coatings was evaluated by the ball-disc wear test. The results show that the growth rate of MAO coating in electrolyte without Na<sub>2</sub>WO<sub>4</sub> is only 0.08<i>μ</i>m/min, meanwhile, the coating is loose and rough, and "networks" connecting with big pores exist on the coating surface.The main phase compositions of this coating are rutile TiO<sub>2</sub>, anatase TiO<sub>2</sub>, Al<sub>2</sub>O<sub>3</sub>, and Nb<sub>2</sub>O<sub>5</sub>. The addition of Na<sub>2</sub>WO<sub>4</sub> in the electrolyte shortens the time before sparking of Ti<sub>2</sub>AlNb alloy, increases the growth rate of the coating, improves the uniformity of coating and meanwhile, a small amount of WO<sub>3</sub> is introduced in the coating. Besides, MAO coatings formed in the participation of Na<sub>2</sub>WO<sub>4</sub> have better wear resistance. Severe abrasive wear occurs when the test is made on Ti<sub>2</sub>AlNb alloy with Si<sub>3</sub>N<sub>4</sub>, the friction coefficient reaches 0.5-0.7. Both the friction coefficient and wear rate decrease obviously when Ti<sub>2</sub>AlNb is treated by MAO. The friction coefficient and wear rate of MAO coating prepared in the electrolyte with 4g/L Na<sub>2</sub>WO<sub>4</sub> are 0.24 and 6.2×10<sup>-4</sup>mm<sup>3</sup>/(N·m), respectively. Only "fish scales" caused by fatigue wear appears on the coating surface. |
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| ISSN: | 1001-4381 1001-4381 |