采用粉末法,在不同Y含量的TiNi形状记忆合金基体上制备了650℃渗铝涂层,并对Y影响涂层的形成以及涂层在700℃恒温氧化性能进行了研究。结果表明:渗铝涂层由外层TiAl3和内层NiAl3构成,涂层的生长主要由Al的内扩散控制。当Y含量低于1at%时,稀土元素Y的添加促进TiAl3外层的生长,抑制NiAl3 内层的生长。恒温氧化实验表明:添加0.5at%Y能明显降低渗铝涂层的氧化速度,但添加1 at%Y和5 at%Y却加速涂层的氧化。并对Y影响涂层的形成以及恒温氧化性能进行了分析。
Ti-Ni shape memory alloys with and without Y addition were aluminized at 650 ℃ using a pack-cementation method. The influences of various amounts of Y additions on the microstructure and the isothermal oxidation behaviors of aluminide coatings in air at 700 ℃ were investigated. The results show that aluminide coatings exhibit double layer structure, and the aluminization process is mainly controlled by the inner diffusion orAl. The Y addition promotes the growth of outer TiA13 layer, but it retards the growth of inner NiA13 layer when Y content is lower than lat%. Isothermal oxidation results indicate that the scale growth rate is significantly reduced when the Y addition is 0.5at%. In contrast, the oxidation rate of Ti-Ni alloy is increased when lat% Y and 5at% Y are added, especially 5at% Y addition. The effect of Y element on the coating formation and the coating oxidation behavior was discussed.