Compositionally Graded Additive Manufacturing: A Method for Alloy Development and Tribocorrosion Evaluation

Additive manufacturing (AM) enables the fabrication of materials with tailored compositional and microstructural gradients, offering unique opportunities for studying complex degradation phenomena such as tribocorrosion. In this work, a thin-walled stainless steel build with a continuous compositional gradient from super-austenitic AL6XN to austenitic 316L was produced using a dual-hopper powder feed system. Energy-dispersive spectroscopy (EDS) confirmed the compositional gradient and corresponding decrease in pitting resistance equivalent number (PREN), while electron backscatter diffraction (EBSD) revealed a microstructural gradient characteristic of thin-walled AM builds, evolving from fine elongated grains near the baseplate to coarser columnar grains at the top. Potentiostatic tribocorrosion testing in 0.6 M NaCl under anodic applied potentials demonstrated that wear rate increased with build height, inversely following the PREN gradient. Microhardness measurements confirmed the additional contribution of microstructural evolution on the local wear resistance which also impacts tribocorrosion performance. Current transients showed higher dissolution activity in 316L-rich regions and lower currents in AL6XN-rich regions, consistent with SEM observations of increased corrosion products in the 316L-regions. These results highlight that tribocorrosion performance is driven by the combined effects of wear resistance and corrosion resistance. More importantly, they demonstrate the utility of AM-graded samples as an efficient platform for screening alloys enabling novel alloy development and as a means for probing the coupled effects of wear and corrosion in tribocorrosion studies.