Investigation of erosion temperature in micro-blasting

Micro-blasting is a non-conventional subtractive micro-manufacturing technology based on erosion localisation and intensification. The thermal aspects of erosion are rarely discussed in the literature and commonly neglected in the analysis of erosion mechanism and quality control of machined surface. This study uses analytical, numerical and experimental approaches to explore erosion temperature in relation to micro-blasting of carbon steels. The research shows that, in terms of temperature, airborne erosion by solid particles is a double-natured process; the surface temperature may increase up to a few thousand degrees Celsius after a single impact, yet it dissipates at the subsurface over several microseconds. Melted and adhered drops of the metallic substrate were found in optical images of abrasive particles and SEM images of a machined surface. EDX elemental analysis confirmed that a thin metal layer was deposited on the particle's interface. Despite this, several FEM models and measurements taken by a thermocouple and IR camera—showed that the steady-state temperature is negligible. The heat generated during each impact has sufficient time to dissipate, leaving a residual temperature of a few degrees before the next impact at the same site. This heat accumulation could elevate the temperature to a few hundred degrees, particularly when the workpiece is small, although convective cooling by air flow effectively dominates this effect. In general, small and slow abrasives are recommended to reduce the temperature. Application of alumina particles smaller than 27 µm to blast low-carbon steels produces minimal negative consequences.