Effect of Si on oxidation kinetics and oxide-scale evolution of W-containing ZG45Ni35Cr26 heat-resistant steel

High-temperature oxidation and scale spallation severely limit the service life of Ni–Cr heat-resistant steels under thermal cycling. This study evaluates how W and Si additions affect the cyclic oxidation behavior and high-temperature strength of ZG45Ni35Cr26 steel in air at 1150 °C for up to 100 h. The base alloy was compared with two W-containing alloys with different Si contents, S1 (2 wt.% W, 1 wt.% Si) and S2 (2 wt.% W, 2 wt.% Si). W addition improves the high-temperature strength of ZG45Ni35Cr26; however, it deteriorates oxidation resistance due to volatilization of WO3, which is associated with cracking and severe spallation of the outer spinel-type oxide scale. In contrast, the introduction of approximately 2 wt.% Si into the W-containing steel leads to a notable improvement in oxidation behavior, characterized by a transition in oxidation kinetics from a linear regime (S1) to parabolic behavior, and reducing mass gain after 100 h of cyclic exposure. Meanwhile, although the high-temperature strength of S2 is marginally lower than that of the low-Si S1 alloy, the dominant strengthening contribution from W ensures that it remains significantly higher than that of the unmodified base alloy. The improved oxidation resistance is attributed to Si-assisted formation of a more protective Cr-rich oxide scale containing a Si-enriched constituent, which enhances scale integrity and reduces ionic transport. These results support a W-Si co-alloying strategy for balancing mechanical strength and oxidation resistance, and indicate that controlling Si to 2 wt.% benefits W-containing ZG45Ni35Cr26 steels for high-temperature glass industry applications.