Influence of plasma beam polishing process parameters on surface roughness of AISI 304 stainless steel

Abstract

Industrial products used in medical equipment and food manufacture are usually made from AISI 304 and place great demands on surface polishing. The application of plasma beam in the field of energy beam polishing is a new technology to obtain a desired level of surface roughness. Therefore, this paper details an investigation conducted to focus on the effect of process parameters on the surface morphology of AISI 304 stainless steel during plasma beam polishing. The main arc current, nozzle height, scanning speed and plasma gas flux that have the greatest influence on the arc plasma characteristics and energy input values are considered to be the key experimental parameters. While the measured roughness values and their intensity autocorrelation functions are applied to evaluate the polished surfaces. The capacity of plasma beam polishing to produce glossy and defect-free surfaces on AISI 304 has been successfully verified. Under the specific combination of main arc current, nozzle height and scanning speed, the energy input could reach approx. 90 J/mm ∼ 110 J/mm, corresponding to the more than 85.9% fall in areal roughness Sa. Although the plasma gas flux had no discernible impact on the energy input, it was observed that the surface uniformity varied from 0.81 ± 0.01 μm Sa to 1.04 ± 0.04 μm Sa with the increase of plasma gas flux. Possible changes of chemical composition and nano-hardness during plasma beam polishing of AISI 304 stainless steel are analyzed.