Oxidation and Nitridation Behavior of Cr–Si Alloys in Air at 1473 K

Abstract

The high-temperature oxidation and nitridation behavior of pure chromium and four Cr–Si alloys (0 < Si < 25 at%) with single phase solid solution Cr(Si), single phase Cr3Si silicide, and two-phase Cr–Cr3Si structures were studied in synthetic air at 1473 K for up to 1000 h. Thermogravimetic analysis of the oxidation kinetics showed that the addition of Si significantly influences the growth and volatilization rate of the oxide scale. The stability of oxides and nitrides in the Cr–O–N and Cr–Si–O–N system were studied. Based on the microstructural evolution of substrate alloys with different silicon content the underlying mechanisms of internal nitridation are discussed. Results showed that addition of only 3 at% Si significantly improved the oxidation and nitridation resistance. Higher Si additions further improved the properties as the single phase Cr3Si silicide remains stable at higher nitrogen partial pressures.