B4C-AISI 434 L steel functionally graded thin wall structures with variable B4C gradient strategies manufactured by TIG PBF-AAM method

Functionally graded (FG) thin wall structures of B₄C-AISI 434 L SS composite have been fabricated using three different B₄C gradient strategies (namely smooth, moderate, and steep) by Tungsten Inert Gas aided Powder Bed Fusion Arc Additive Manufacturing (TIG PBF-AAM) method. For all different strategies, towards the building direction, substantial variations in the grain structure, phase composition, microhardness, and wear- and scratch- resistance were witnessed. The SEM images and the XRD analysis of the FG structures indicate the dilution of B₄C and formation of iron boride (Fe₂B, FeB) phases, which is largely influenced by the B₄C proportion in a specific region. An increased B₄C content towards the building direction unveiled a higher fraction of unreacted B₄C phase, which augmented the hardness and wear resistance of the gradient structure expressively. Due to gradual transition in the microstructure, a steady increment in the hardness value was perceived for smooth gradient, and accordingly minimum wear loss (27 μm, 0.00243 g, or 1.45 × 10⁻⁴ mm³/N-m) was recorded. While, the moderate and steep gradient structures exhibited sharp transitions of microhardness at the interfaces, and amplified the wear loss consequently. This work demonstrated the potential of TIG PBF-AAM method to fabricate FG parts with tailored microstructure and mechanical properties required for tribological applications, where a hard surface and impact-tolerant base are foremost significant.