Effect of Cr addition on the phase equilibria and oxidation behavior of NbSi 2 was investigated. Although the crystal structures of NbSi 2 and CrSi 2 are both C40, they form separated ranges of homogeneities in the NbCrSi ternary system. The vertical section passing through the NbSi 2 and CrSi 2 binary edges were experimentally determined. A binary NbSi 2 alloy exhibited poor oxidation resistance, showing pest-like behavior upon cyclic oxidation at temperatures from 800 to 1200°C. On the other hand, Cr addition significantly improved the oxidation resistance of NbSi 2 . The oxide layers that developed on the NbCrSi ternary alloys consisted of NbCrO 4 , Cr 2 O 3 , and SiO 2 , and the formation of Cr 2 O 3 and NbCrO 4 suppresses the Nb 2 O 5 formation, and thereby suppresses the pest-like behavior of the binary NbSi 2 alloy. However large Cr additions that exceed the solubility limit of NbSi 2 should not be suitable, because NbSi 2 /CrSi 2 alloys were susceptible to spalling and disintegration of the oxide scales upon cyclic oxidation. [

The phase equilibrium and oxidation behavior of the disilicides that form in the Nb-Cr-Si ternary system have been investigated. Although NbSi2 and CrSi2 both exhibit a C40 crystal structure, they form separate ranges of compositional homogeneity in the ternary system. Their phase boundaries at 1300 °C have been experimentally determined in this study. The binary NbSi2 exhibited poor oxidation resistance, showing pest-like behavior during oxidation at temperature above 800 °C. In contrast, the alloys containing Cr showed much better oxidation resistance up to 1200 °C.