Innovative Al–Ni–Ir alloy for bond coats: Microstructure, phase analysis and oxidation behaviour

摘要: Iridium modified nickel alluminides are considered promising bond coats due to the capability promote α-Al2O3 scale growth and develop formation of Ir layer acting as oxygen diffusion barrier (ODB). An innovative Al–Ni–Ir alloy (Al 60 %at, Ni 35 5 %at) was formulated, taking into account coat appropriate requirements cost standpoint. A detailed systematic microstructural investigation both powder bulk samples reported, comparing phase composition, thermal stability oxidation behaviour proposed system with respect free one. The analysed AlNiIr composed Al3Ni2 AlNi3, in addition β-NiAl, detected reference presence seemed alumina growth, starting at around 1000 °C. Both cast oxidised showed Ni-poor Al-rich islands, which resulted more concentrated, suggesting an iridium higher affinity towards Al Ni. After operative temperature (i.e. 1150 °C), observed, increasing thickness dwelling time. Neither ODB nor rich islands interface between Al2O3 were identified, low amount. However metallic compound Al2.75Ir after treatment