TC4合金表面激光熔覆TiAl涂层的高温循环氧化行为

High-temperature cyclic oxidation behavior of laser cladding TiAl coating on TC4 alloy surface

采用激光熔覆工艺在TC4基体表面制备了TiAl涂层,分别对TC4基体与TiAl涂层在600、800、900和1000℃下开展了循环氧化50 h实验,分析TC4基体与TiAl涂层在不同温度下的氧化动力学行为、氧化膜的物相、表面形貌及元素分布,并对其高温氧化机理进行了阐述。结果表明:涂层氧化动力学曲线近似符合抛物线规律,且单位氧化质量增加和氧化速率均比TC4基体小。TiAl涂层在600、800、900和1000℃下的氧化质量增加分别为TC4基体的12.5%、20%、55.6%和35.7%。TiAl涂层的氧化产物主要为Al_(2)O_(3)和TiO_(2),在600~900℃之间氧化物均匀致密无破损,在1000℃下出现氧化膜的破损、剥落。TiAl涂层的氧化极限较TC4基体至少提高300℃,表现出优异的高温抗氧化性能。

TiAl coating was prepared on the surface of TC4 substrate by laser cladding process.The oxidation behavior of TC4 substrate and TiAl coating were carried out at 600,800,900 and 1000℃for 50 h,respectively.The oxidation kinetics behavior,phase composition,surface morphology and element distribution of the oxide film of TC4 substrate and TiAl coating at different temperatures were analyzed,and the high temperature oxidation mechanism was expounded.The results show that the oxidation kinetics curve of the coating approximately conforms to the parabolic law,and the unit oxidation mass gains and oxidation rate are smaller than those of TC4 substrate.The oxidation mass gains of TiAl coating at 600,800,900 and 1000℃are 12.5%,20%,55.6%and 35.7%of those of TC4 substrate,respectively.The oxidation products of TiAl coating are mainly Al_(2)O_(3)and TiO_(2).At 600−900℃,the oxide is uniform and intact without cracks.The oxide scale is damaged and exfoliated at 1000℃.The oxidation limit of TiAl coating is at least 300℃higher than that of TC4 substrate,showing excellent high-temperature oxidation resistance.