The effect of temperature on the cryogenic abrasive jet micro-machining of polytetrafluoroethylene, high carbon steel and polydimethylsiloxane

A previously developed cryogenic abrasive jet micro-machining apparatus was used to machine polytetrafluoroethylene (PTFE), high carbon steel, and polydimethylsiloxane (PDMS) at temperatures between −182 °C and 17 °C. As the machining temperature was lowered, the maximum erosion rate of PTFE increased five-fold and was found to occur at progressively higher angles of attack, shifting from 15° to 90°, although the angular dependence weakened and the maximum became less pronounced. This was similar to the behavior of PDMS observed in an earlier study [1]. The dependence of the erosion rate on angle of attack in high carbon steel, a useful masking material, was found to be insensitive to temperature, but the erosion rate increased approximately two-fold as the temperature decreased from 17 °C to −182 °C. The cross-sectional profiles of masked, machined micro-channels in PDMS and PTFE had relatively steep sidewalls compared to glass channels, even at the lowest temperature of −182 °C, which indicates erosion was still not fully brittle. Predictions of the evolution of the channel cross-sectional profiles generally agreed well with experiments, although the channel width in PDMS at −182 °C was under-predicted, most likely due to thermal effects. None of the materials exhibited an erosion incubation period, and there was minimal particle embedding in the samples machined below room temperature.