Effect of Varying Layer Thickness by Interlayer Machining on Microstructure and Mechanical Properties in Wire Arc Additive Manufacturing

This study investigates the influence of varying layer thickness through interlayer machining in Wire Arc Additive Manufacturing (WAAM) and its impact on microstructural evolution, mechanical properties, and residual stress distribution. It compares four types of WAAM samples: As-built with uneven layer thickness without interlayer machining and uniform layer thicknesses of 2 mm, 1.5 mm, and 1 mm achieved through interlayer machining. As-built components exhibited coarse columnar grains and uneven deposition, adversely affecting hardness and strength. Interlayer machining at reduced layer thickness refined grains, restricted growth, and induced plastic deformation, leading to enhanced mechanical properties. Grain refinement achieved reductions of 62.7% (top), 77.6% (middle), and 64.3% (bottom), significantly improving microstructural uniformity. Microhardness increased from 150 to 180 HV (as-built) to 210 to 230 HV (machined to maintain 1 mm layer thickness), marking a 40–43% improvement. Tensile strength was enhanced, with UTS increasing from 494.72 MPa to 582.11 MPa (17.6%) and YS from 371 MPa to 471 MPa (26.9%), although elongation decreased from 59% to 46% (22% reduction). Residual stress was reduced by 55–60%, improving structural integrity. These findings highlight interlayer machining as a key strategy for optimizing WAAM-fabricated components while balancing mechanical performance and manufacturing efficiency.