Tensile behavior of a slurry Fe-Cr-Si coated Nb-alloy evaluated by Gleeble testing

Fe-Cr-Si coated Nb-alloy C103 is a strategic material for advanced structural high temperature applications in hyperplanes. The coating provides oxidation resistance and is indispensable for high-temperature use of the C103 alloy. However, the coating is constituted of brittle intermetallic silicide phases, which can affect the tensile properties of the substrate adversely. The present paper examines the effect of coating on the tensile properties of C103 alloy. The tensile properties have been evaluated at various temperatures up to 1500 °C using the Gleeble test facility. For low test temperatures up to 900 °C, the coating exhibited extensive brittle cracking and spallation, which caused reduction in the YS and UTS of the substrate alloy by 10-20%. On the other hand, the coating showed ductile deformation and it did not affect the strength of the alloy at temperatures of 1100 °C and above. At all test temperatures, the substrate alloy was ductile enough to resist the penetration of the coating cracks into the substrate, and the ductility of the alloy was not affected significantly by the application of the coating. The fracture behavior in the coating at various temperatures and implications on the tensile behavior of the substrate alloy are discussed.