Effects of tungsten content on the high-temperature oxidation behavior of Ni-xW-6Cr alloys

[Display omitted] •The oxidation kinetics of the Ni-xW-6Cr alloys at 850 °C are not direct function of W content.•The external formation of NiCr2O4 is facilitated by W acting as secondary getter.•The excessive W (above 25 wt.%) forms CrWO4, preventing the formation of protective NiCr2O4.•Inner NiWO4 scale weakens the adhesion of oxide to the matrix, leading to the cracks. The oxidation of Ni-(5–30 wt.%) W-6 wt.% Cr alloys was studied at 850 °C in air, among which Ni-25 W-6Cr alloy shows the best oxidation resistance. Because W acts as secondary getter, an external continuous oxide scale (NiCr2O4) is formed, which is responsible for the excellent oxidation resistance of these alloys. When the W content reach above 25 wt. %, the excessive W can facilitate the growth of CrWO4, preventing the formation of NiCr2O4, and breaking the continuity of the chrome oxide scale. Additionally, NiWO4 formed near the metal-scale interface can weaken the adhesion of oxide scales, causing cracks.