Adsorption and reaction layers when turning AISI 304 using various cooling strategies

摘要

This paper deals with the surface chemistry of face-turned workpieces of AISI 304 using various cooling conditions. The workpieces were machined by means of LN2cooling, CO2snow cooling, conventional emulsion, sub-zero MWF as well as dry machining. With regard to the machining process, the tool temperature, the process forces, and the surface topography are investigated. The surface chemistry is studied using X-ray photoelectron spectroscopy (XPS). These investigations focus firstly on a detection of the elements occurring on the surface, their concentration and the dominant binding state of the main components. Especially the oxidation state of the surface due to the thermal load in the tool-work interface during machining is analyzed on the basis of O 1s and Fe 2p3 core level photoelectron spectra. Secondly, sputter depth profiling using XPS is performed in order to qualitatively analyze the surface depth distribution of the detected elements. Adsorption and reaction layers can occur during turning of AISI 304 up to a depth of approximately 7 nm depending on the cooling conditions used. The use of emulsion, CO2snow and dry machining results in a slightly higher carbon concentration. Regarding the oxidation in the reaction layer it can be concluded, that the higher the temperatures in the tool at distance of 1 mm to the contact zone during machining, the more oxidation occurs in these layers.