Macrohardness-Based Spatial Homogeneity Analysis of TIG-Welded AISI 304 Stainless Steel

This study evaluates a material homogeneity criterion (MHC)-based workflow for the spatial characterization of macrohardness variability in tungsten inert gas (TIG) welded AISI 304 stainless-steel joints produced using 308LSi filler metal. Five welded specimens produced under different welding conditions were first evaluated by transverse tensile testing. Two specimens representing contrasting mechanical responses were subsequently selected for identical spatial macrohardness mapping: Specimen 1 exhibited the lowest ultimate tensile strength (610 MPa), 24% elongation, and fracture through the weld region, whereas Specimen 3 exhibited the highest ultimate tensile strength (684 MPa), 41% elongation, and fracture in the base material. For each specimen, 1000 Rockwell macrohardness (HRBW) measurements were obtained along twenty transverse measurement lines spanning the base material (BM), heat-affected zone (HAZ), and fusion zone (FZ). Mean hardness ranges were comparatively similar for Specimens 1 and 3 (92.04–95.70 and 92.00–95.50 HRBW, respectively). Meanwhile, the coefficient of variation (CV) and Weibull homogeneity coefficient (WHC) provided greater discrimination between the two joints. Specimen 1 exhibited CV values of 0.534–1.433% and WHC values of 81.20–216.95, whereas Specimen 3 exhibited CV values of 0.542–1.076% and WHC values of 107.87–214.12. The largest between-specimen difference was observed within the HAZ, where Specimen 1 exhibited substantially greater macrohardness dispersion than Specimen 3. These results show that statistical treatment of repeated macrohardness measurements can reveal spatial differences between welded joints that are less evident from mean-hardness profiles alone. The comparison does not establish a general predictive relationship between hardness dispersion and tensile performance but provides experimental evidence supporting the discriminatory value of spatial CV and WHC mapping for the two investigated contrasting cases. Optical metallography provides complementary qualitative microstructural characterization, while quantitative relationships between microstructural parameters and macrohardness dispersion remain outside the scope of the present study.