高温氧化对钛合金微弧氧化陶瓷膜组成与结构的影响

针对钛合金不耐高温氧化的问题,在铝酸钠电解液体系中,利用双相脉冲直流微弧氧化技术,在TC4钛合金表面原位生长以Al2TiO5为主晶相的复合氧化物陶瓷膜,研究了1000℃高温氧化对陶瓷膜试样的相组成、结构的影响及膜层增重特点.研究表明,陶瓷膜层试样的高温氧化过程包括Al2TiO5分解、基体氧化和膜层表面形貌变化3个方面.高温氧化后,膜层的主晶相由Al2TiO5变为α-Al2O3和金红石型TiO2,同时,膜层的表面形貌发生显著的变化;由于膜层和基体的热膨胀系数不同和基体钛的氧化,使得高温氧化后膜层在冷却过程中表面出现裂纹和脱壳.陶瓷膜层极大地减少了TC4钛合金在1000℃高温氧化时的增重,因此,陶瓷膜层可用于TC4钛合金的恒温氧化防护.

Effects of high temperature oxidation on composition and structure of microarc ceramic coating on Ti alloy

Due to the poor high temperature resistance of Ti alloy,ceramic coatings with the main crystalline of Al2TiO5 were prepared on TC4 alloy in NaAlO2solution by pulsed bi-polar microarc oxidation technique.And the effects of high temperature oxidation at 1000 ℃ on composition,structure and the weight gains of ceramic coatings were investigated.The results showed that the oxidation process of the ceramic coatings included the decomposition of Al2TiO5,the oxidation of the substrate and the changes of the coating morphology.After high oxidation,the main crystalline of the coating became α-Al2O3 and rutile TiO2 from Al2TiO5,and the surface morphology of the coatings changed greatly.Because of the different heat expansion coefficients between the substrate and the coating and the oxidation of the substrate in itself,the coatings cracked and separated from the substrate during the cooling process.Compared with the substrate,the ceramic coatings greatly decreased the weight gains of the TC4 alloy under the high temperature oxidation of 1000℃.Therefore,the ceramic coatings may be used as a kind of isothermal oxidation resistance coating in practice.