3D printed N-doped CoCrFeNi high entropy alloy with more than doubled corrosion resistance in dilute sulphuric acid

The traditional approaches for improving corrosion resistance of alloys typically lead to the sacrifice of mechanical properties because the microstructures needed for improving corrosion resistance often contradict those for high strength. Here we demonstrate that selected laser melting (SLM), a net-shape additive manufacture technique, can maintain good mechanical properties while double the corrosion-resistance of a N-doped CoCrFeNi HEA. The SLM processed sample possesses a heterogeneous microstructure with 3D dislocation cells inside each grain. The SLM-induced 3D dislocation cell structure can provide effective diffusion paths to significantly promote Cr outward segregation, forming a thick protective Cr oxide layer, which renders excellent corrosion resistance. Furthermore, Cr segregation along cell boundaries provides numerous sites for nucleation of oxides, and stabilizes the cell structure for good mechanical properties. The strategy discovered here may also be applied to other HEAs with multiple strengthening mechanisms.

Automated summary

Traditional methods to improve corrosion resistance of alloys often sacrifice mechanical properties. However, we demonstrate that selective laser melting (SLM) can double the corrosion resistance of a N-doped CoCrFeNi HEA while maintaining good mechanical properties. The SLM process creates a heterogeneous microstructure with 3D dislocation cells, promoting Cr outward segregation and forming a thick protective Cr oxide layer for excellent corrosion resistance. Furthermore, Cr segregation along cell boundaries provides nucleation sites for oxides and stabilizes the cell structure for good mechanical properties. This strategy may be applicable to other HEAs with multiple strengthening mechanisms.