超音速火焰喷涂NiTi合金涂层的形状记忆效应

采用超音速火焰喷涂制备超致密NiTi合金涂层,通过后续热处理获得优化相变结构,并通过压痕法分析涂层的形状记忆效应。光学显微镜及扫描电镜对NiTi合金涂层微观结构表征显示,喷涂制备态涂层由内部岛状-链状界面叠片组成,涂层致密孔隙率约为0.82%。X射线衍射分析显示,NiTi涂层制备态为全奥氏体,经时效处理析出Ni₄Ti₃相。压痕法分析表明,在制备态及时效态涂层中均获得了一定的单程及双程形状记忆效应。X射线物相分析及差示扫描量热仪对比分析揭示,时效析出的第二相粒子显著增加形状记忆效应。

Shape memory effect of NiTi alloy coating deposited by high-velocity oxygen-fuel spraying

A highly dense NiTi alloy coating was prepared by high-velocity oxygen-fuel (HVOF) spraying, and the microstructure was optimized by subsequent aging treatment. The shape memory effects of the as-HVOF sprayed and as-aged specimens were evaluated through an indentation method. The OM and SEM microstructural characterization show that the as-sprayed NiTi coating consists of laminated internal island-chain interfaces, with a porosity of about 0.82%. The X-ray diffraction analysis shows that the as-sprayed NiTi coating owns 100% austenite, from which the Ni₄Ti₃ phase precipitates out in aging treatment. The indentation analysis shows that both the one-way and the two-way shape memory effects can be induced in the as-sprayed and the aged coatings, while the X-ray phase analysis and the differential scanning calorimetry analysis show that the shape memory effect is significantly increased by the precipitated second phase particles in aging treatment.