Data of Physics-informed plume diagnostics for process-structure-property relationships in AC-HVAF thermal spray processing

This work proposes a physics-informed diagnostic framework to establish process-structure-property relationships in activated-combustion high-velocity air-fuel (AC-HVAF) thermal spray deposition. The methodology integrates optical plume diagnostics, thermodynamic equilibrium calculations, digital image analysis, and regression analysis to identify process variables and relate plume descriptors to coating response. Plume diagnostics were conducted under steady-state conditions without powder injection to isolate gas-phase combustion and jet characteristics. Plume descriptors were extracted from calibrated imaging data and correlated with process variables. Thermodynamic equilibrium calculations were used to estimate relative combustion trends through the adiabatic flame temperature and equivalence ratio. A stable operational regime was identified within a narrow near-stoichiometric window, characterized by well-defined shock-diamond structures and enhanced plume collimation. Within this regime, two representative alloys were deposited: a Co-Cr-W-C alloy and a Ni-Cr-Si-B self-fluxing alloy. Multivariate regression analysis revealed strong correlations between plume metrics, normalized processing variables, and coating properties, including thickness, microhardness, and porosity. The resulting coatings exhibited porosity below 5% and microhardness values in the range of 511-632 HV0.3. The results show that near-stoichiometric combustion regimes associated with elongated and collimated plumes favor coating formation with lower porosity and higher hardness, consistent with improved particle deformation and enhanced thermal and kinetic transfer inferred from the plume descriptors. The proposed framework provides a diagnostic-assisted route to relate combustion conditions, plume morphology, and coating characteristics in AC-HVAF thermal spray processing, while clarifying the role and limitations of plume descriptors as indirect indicators of particle thermal and kinetic states.