Interface stability of NiCrAlY coating without and with a Cr or Mo diffusion barrier on Ti-42Al-5 Mn alloy

Abstract NiCrAlY coatings without and with a Cr or Mo diffusion barrier were fabricated on Ti-42Al-5 Mn alloys by vacuum plasma spray. The microstructure evolution and inter-diffusion behavior were studied via isothermal oxidation tests conducted at 950 °C. The results revealed that substantial inter-diffusion happened in the coating without a diffusion barrier, accelerating the degradation of NiCrAlY coating. While the addition of Cr or Mo diffusion barrier deferred the inter-diffusion phenomenon, and Mo performed much better than Cr due to its high stability. The thickness of the inter-diffusion zone with the Mo diffusion barrier was just about one-fifth of that for NiCrAlY coating after 200 h oxidation. The results could provide comprehensive understanding of the microstructural evolution of NiCrAlY coating, which was essential for controlling the inter-diffusion behavior and improving the durability of NiCrAlY coating.