Additive manufacturing of a new Fe-Cr-Ni alloy with gradually changing compositions with elemental powder mixes and thermodynamic calculation

It is becoming an urgent need to synthesize novel alloy possessing both corrosion resistance and sufficient plasticity to meet various functionality requirements in severe corrosion working environment. This study introduced a new Fe-Cr-Ni-based alloy with gradient composition which was fabricated by additive manufacturing with pre-mixed elemental powder. A thin wall sample was fabricated from bottom to top layer by layer following four composition designs (Fe-16Cr-8Ni, Fe-14Cr-16Ni, Fe-12Cr-23Ni, and Fe-9Cr-28Ni) to achieve the transition from ferritic phase to austenite phase. The elemental powders' shape and size distribution were characterized and analyzed first. The mixing enthalpy for the three elements was studied since it can impact on the deposits homogeneity. Microscopic metallography of the sample was acquired to analyze the microstructure. Then, the phase identification was investigated by X-ray diffraction (XRD). Energy dispersive spectroscopy (EDS) analysis examined the composition in the sample. The results indicate that the microstructure of regions with 8 and 16% of Ni was mainly the lathy and skeletal morphologies, while standard austenite morphology, cells, and dendrites were observed in the regions with 23 and 28% Ni. Then, Vickers hardness test was used to observe the gradually changing hardness profile. In addition, a thermodynamic modeling was employed to predict the Fe-Cr-Ni alloy's formed phase at room temperature, then compared with the XRD pattern. The experimental-computational approach described herein for characterizing the new Fe-Cr-Ni alloy can be used to improve the understanding and design of other new alloys.