The incorporation of Cr in enhancing the corrosion resistance, mechanical property and thermal stability of NbMoTaCrx coatings

Refractory high-entropy alloy (RHEA) coatings with superior corrosion, mechanical properties and thermal stability are promising for complex environments such as high-temperature and multi-factor coupled corrosion conditions. The effects of Cr (Chromium) on the corrosion and thermal stability of NbMoTaCr x coatings are investigated. Results demonstrates that NbMoTaCr 1.4 coating has the optimal corrosion performance, with the highest corrosion potential of −0.16 V and lowest corrosion current density of 0.01 μA cm −2 . The passive film of NbMoTaCr 1.4 coating is relatively more stable due to its higher reduction potential and lower semiconductor Fermi level. BCC (body-centered cubic) solid solution structures are retained even annealed at 800 °C, revealing good thermal stability of NbMoTaCr x coatings. 400 °C-annealed NbMoTaCr 1.4 coating with fine grain sizes has a higher hardness of 11.4 GPa. Solid solution strengthening effects are dominated by modulus distortion of all NbMoTaCr x coatings, and smallest atomic size distortion exhibits in equiatomic NbMoTaCr coating. In conclusion, the incorporation of Cr significantly enhances the corrosion and mechanical properties, and the NbMoTaCr x coatings possesses excellent thermal stability. • NbMoTaCr x coatings with varying Cr contents are deposited using magnetron co-sputtering. • NbMoTaCr 1.4 possesses the superior corrosion resistance with higher E corr and lower i corr . • The passive film on the NbMoTaCr 1.4 coating is stabler with higher reduction potential and lower semiconductor Fermi level. • NbMoTaCr x coatings exhibit excellent thermal stability with BCC structure maintaining stable up to 800 °C. • Modulus distortion predominates in the solid solution strengthening of NbMoTaCr x coatings.