Investigations on the Thermal Cycling Stability of SiFeCr Coated NbtZr

 Refractory metal alloys play an important role as highly thermostable materials. Due to their lack of oxidation stability under elevated temperatures it is necessary to protect them with coatings. The thermal cycling stability of Si20Cr20Fe-coatings on Nb10W2.5Zr was investigated by means of imaging secondary ion mass spectrometry showing the inward-diffusion of oxygen and subsequent preferential precipitation of zirconium oxides at the grain boundaries in the bulk. An unintentional interface layer of high boron content that most likely plays a major role in oxidation protection was found. EDX measurements have been performed to investigate on the phases formed in this complex system.