Deriving of process signature correlation on measurable material loading for process optimization: A case study of thermal spray of cemented carbide coatings

The multiple process parameters of a product coupled with materials of design have a profound influence on its performance. To enable a practical knowledge-based method of process optimization, process signature is explored with respect to surface integrity as a pivot in the material-product-process linking, as represented by thermal spraying of WC-Ni coatings for coated products utilizing the online measurable material loading, i.e. the in-flight particle temperature and velocity. The process signature correlations, from multiple process parameters of oxygen/fuel flow rates and spray distance to multiple surface integrity parameters of coating microstructures and mechanical properties, are explored in two steps via the measurable material loading. A process-dependent correlation from process parameters to the particle temperature and velocity of in-flight particles in spray flame is firstly established by identifying a characteristic process quantity of fuel/oxygen ratio that mainly controls the flame temperature, and a characteristic processing load of combustion pressure that controls the flame flow velocity. Subsequently, a partially process-independent correlation coupled with spray distance effect is derived from the particle deposition temperature/velocity to the coating microstructures and mechanical properties. Finally, a process-independent correlation is derived as the thermal and kinetic energies of coating formation correlating to the surface integrity parameters by thermodynamic analysis with incorporated spray distance effect. The study provides a feasible methodology of process signature derivation for practical implementation in process optimization and control for advanced manufacturing development. • Process signature correlations explored in a case study of thermal spray process • Correlations from process to surface integrity based on measurable material loading • Process-dependent correlation of process parameters to material loading is derived. • Partially process-independent correlation to surface integrity parameters is derived. • Process-independent correlation to surface integrity is derived on thermodynamics.