添加K_2ZrF_6对钛合金微弧氧化膜层组织结构的影响

Effects of K_2ZrF_6 additive on microstructure of micro-arc coatings fabricated on TA15 alloy

采用交流电源对TA15合金进行微弧氧化处理,研究了在NaAlO2-Na3PO4溶液体系中添加K2ZrF6对膜层组织结构的影响.利用XRD、SEM和EDS等手段分析了膜层的相组成及表面形貌,探讨了添加剂K2ZrF6对成膜速率、膜层结构的影响,借助热震实验研究了陶瓷膜与基体的结合力,并利用热阻隔性能测试评价了不同溶液中所形成膜层的热阻隔效果.加入K2ZrF6后,微弧氧化的成膜速率增加.SEM结果表明:K2ZrF6使膜层表面粗糙度降低,膜层内部缺陷减少.EDS线扫描分析表明:添加K2ZrF6后氧化膜层中出现大量锆元素,且其含量随距膜/基界面距离的增加而增加.XRD结果显示,未添加K2ZrF6溶液制得的膜层主要由Al2TiO5和Rutile-TiO2相组成;而添加K2ZrF6后,膜层中生成了隔热性良好的ZrO2相.热物性相关测试显示:经K2ZrF6调制后的膜层抗热震性能降低,但具有更加优良的热阻隔性能.

Zr-containing ceramic coatings were fabricated on TA15 alloy by micro-arc oxidation（MAO） using K2ZrF6 as a special additive in NaA1O2-Na3PO4 base electrolyte. The effects of K2ZrF6 addition on microstructure, element distribution and phase composition of ceramic coating were analyzed by XRD, SEM and EDS, respectively. The thermal shock resistance and heat resistance of the coating formed on TA15 alloy in different electrolyte were investigated. The results show that K2ZrF6 addition can increase the MAO rate and significantly alter the microstructure of ceramic coatings. Surface of MAO coatings fabricated in Zr-containing electrolyte becomes relatively smooth. Compared with the coating formed in Zr-free electrolyte, a large amount of Zr element is found in the coating formed in Zr-containing. Two main phases, A12TiO5 and Rutile-TiO2 are contained in Zr-free coating. In contrast, t-ZrO2 and m-ZrO2, with excellent heat resistance, are found in Zr-containing coating. Experi- mental results also demonstrate that the thermal shock resistance of the Zr-containing coating is lower but its heat resistance is improved.