Achieving illustrious friction and corrosion resistance on a laser powder bed fusion nitinol rare earth alloy

Abstract

Recently, laser powder bed fusion of nitinol alloys (LPBF-NiTi) has attracted much attention due to its ability to precisely form complex parts. However, the wear and corrosion resistance is crucial for practical applications of LPBF-NiTi alloys. Rare earth oxides are common additives used to improve the surface properties of alloys. In this work, nano-sized cerium oxide (CeO2) is selected as the additive, and the influence rule and mechanism of different addition amounts of CeO2 on the surface properties of LPBF-NiTi alloy are deeply studied. The results showed that the addition of an appropriate amount of CeO2 (0.03 wt% CeO2 addition) could effectively refine the grains and improve the grain order, which achieved the improvement of the mechanical properties (tensile strength and toughness) of the LPBF-NiTi alloy. Furthermore, the reduction in friction coefficient and wear scar depth/width proved that the addition of CeO2 effectively improves the wear resistance of LPBF-NiTi alloys, which were mainly attributed to the synergistic action of the precipitation of the secondary hard phase (NiCe), the grain refinement strengthening, and stable phase transformation brought about by high latent heat of transformation. In addition, the improvement of anti-corrosion was reflected in the reduction of corrosion current density Icorr and pitting pits, mainly due to the formation of NiCe precipitates and grain refinement, which effectively hindered the propagation and extension of pitting corrosion. Most significantly, the 0.03% CeO2 sample achieved the simultaneous improvement of mechanical properties and surfaced functional properties, which greatly expanded the application prospects of NiTi–CeO2 alloys.