Microstructural Evolution and Morphological Aspects of Titanium Carbides in Weld-Deposited Coatings using Chip-Based Fluxes

Abstract

Abstract This work examines how joint design–controlled dilution governs microstructural evolution and titanium carbide morphology in GTAW cladded hardfacing layers produced using recycled Ti6Al4V chips and graphite. Hardfacing coatings were deposited into V-groove geometries of varying depths alongside flat surface configurations to investigate the effect of joint geometry on deposit composition and macrostructure. To account for concave bead profiles, a refined mathematical model tailored to V-groove cross-sections was implemented, providing an effective practical alternative to relate joint preparation to dilution. Microstructural and phase characterizations confirmed a nearly complete conversion of titanium into TiC within a ferritic/martensitic matrix, alongside cementite formation in the synthesized composite hardfacing layer. Elemental analysis revealed that vanadium dissolves into the carbide lattice forming a (Ti, V)C solid solution, whereas aluminium partitions entirely into the metallic matrix as a solid solution element. Without secondary phase formation at these concentration levels, the ternary Fe–Ti–C phase diagram remains a valid thermodynamic framework for accurately predicting TiC morphological evolution during solidification. Increasing flux mass reduced dilution and altered weld pool chemistry, driving a clear morphological transition from fine, dispersed TiC particles at high dilution to coarse dendritic structures under low dilution. Elevated titanium concentrations detected within the matrix under low-dilution conditions confirm high solute availability during solidification, which actively promoted lateral growth above the system liquidus line.