Effect Of Corrosive Medium And Heat Treatment Temperature On Corrosion Properties Of 3D Printed NiFeCrMo Alloys

Three-dimensional printing technology is a new revolution in the field of materials,and with the continuous advancement of this technology,the focus on corrosion problems is particularly important.Nickel-based alloys have excellent corrosion resistance,which provides an opportunity to delve deeper into corrosion issues.However,the corrosion resistance of 3D printing nickel-based alloys in different media is not clear,and the influence of heat treatment temperature on its corrosion resistance is also of urgent concern.In this thesis,3D printed Ni₄₈Fe₂₄Cr₂₂Mo₆alloy was selected as the research object,and the corrosion behavior of this series of alloys in 3.5wt%NaCl,1 M H₂SO₄and 1 M KOH corrosion media was studied,and then the effect of heat treatment temperature on the microstructure and corrosion properties of the alloy was discussed.Test methods and systems such as scanning electron microscope,X-ray diffraction analyzer,electrochemical workstation,XPS passivation film composition analysis were used to reveal the correlation between the influence mechanism and structure of the corrosion resistance of 3D printed NiFeCrMo alloys.The main findings are as follows:（1）X-ray diffraction pattern showed that NiFeCrMo alloy was face-centered cubic single phase,the microstructure was finely equiaxed crystal distribution,and the surface of the alloy had no defects such as pores and cracks.Cr,Mo and other elements in 3D printed NiFeCrMo alloy are enriched at grain boundaries;The enrichment of Cr and Mo elements in the cast NiFeCrMo alloy is not obvious,and the Cr rich phenomenon of 3D-Z is more obvious.（2）In different corrosive media,according to the self-corrosion current density in the potentiodynamic polarization curve and the charge transfer resistance in the electrochemical AC impedance spectrum,it was found that 3D-Z had the highest corrosion performance in 3.5wt%NaCl,1 M H₂SO₄and 1 M KOH solution,and according to the surface corrosion morphology and the composition of XPS passivation film,it was concluded that the 3D printed NiFeCrMo alloy Z direction passivation film was enriched with more Cr elements in 3.5wt%NaCl and 1 M H₂SO₄solution The presence of the enrichment of Mo elements in 1 M KOH solution can make the formed passivation film more stable and more corrosion-resistant.The comprehensive results show that the order of corrosion resistance is 3D printed NiFeCrMo alloy Z direction>3D printed NiFeCrMo alloy XY direction>Cast NiFeCrMo alloy.（3）After 1 h of different heat treatment temperatures,the grain size of 3D printed NiFeCrMo alloy did not change significantly,and the XRD structure was still face-centered cubic single phase after characterization.According to the self-corrosion current density in the potentiodynamic polarization curve,the charge transfer resistance in the electrochemical AC impedance spectrum and the surface corrosion morphology characterization,the corrosion resistance of 3D printed NiFeCrMo alloy weakened after 1 h heat treatment at 1000°C,because after 1 h heat treatment at 1000°C,the Cr rich phenomenon at the grain boundary of 3D printed NiFeCrMo alloy weakened,indicating that 1000°C is not suitable as the heat treatment temperature of 3D printing NiFeCrMo alloy.Selectable temperature ranges of 800-900°C and 1100°C.