Thermal Fluctuations on the Corrosion Behaviour of 17-4PH Stainless Steel Alloys Fabricated via Material Extrusion Additive Manufacturing Technique

Herein, the influence of fluctuating thermal conditions on the corrosion behaviour of 17-4PH stainless steel alloys manufactured via fused filament fabrication is reported. The printed samples were sintered and then exposed to different temperature-fluctuating conditions to simulate the application environment of such alloys. The first set of samples (A) was studied as-sintered, the second set of samples (B) was aged at 480°C for 3 hrs followed by quenching in water, the third set (C) was exposed to conditions of B followed by aging at 360°C for 3 hrs and quenching in water and the final set of samples (D) was exposed to conditions of C followed by aging at 200°C for 3 hrs, quenching in water, aging at 400°C for 3 hrs, and finally quenching in water. The surface roughness evolved with the temperature conditions. The optical microscopy revealed that sample B had a fine and homogenous distribution of precipitates. Sample B had the highest microhardness values followed by C, D, and A in that order. XRD analysis revealed the presence of retained FCC austenitic phases within the microstructure whose peaks became stronger with the increased thermal fluctuations. The potentiodynamic polarisation studies revealed a distinct linear Tafel region on the cathodic region and a dual-slope inflection point on the anodic region of the polarisation curves. Sample D exhibited the highest corrosion rate whereas sample B revealed the lowest. As such, exposing fused filament fabricated 17-4 PH SS to fluctuating temperature conditions leads to degradation of mechanical strength and corrosion resistance.