Hydrodynamic profiling and grit blasting of low-carbon steel surfaces

The surface preparation by hydrodynamic profiling and grit blasting of low-carbon steel specimens is investigated. Roughness measurements and SEM imaging show that hydrodynamic profiling forms a surface profile with a high roughness and without surface contamination. In contrast, grit-blasted specimens show grit residues embedded in the substrate surface. The debris collected after hydrodynamic profiling show a rounded shape suggesting that the material is removed due to low-cycle fatigue. The debris produced by grit blasting appear in the shape of platelets and flow-type chips suggesting a mixture of micro-cutting and forging-extrusion. The influence of stand-off distance, exposure time, and flow speed on the profiling process are also studied. The results identified the optimum operational conditions for hydrodynamic profiling. Fatigue by impacting fluid drops is suggested to be the dominant material failure mode. However, results of a comparative calculation of the incubation drop impact frequency suggests that fatigue is accompanied by energy-dissipative processes.