Mechanistic study on micromilling of the super duplex stainless steel UNS S32750

Super duplex UNS S32750 is an important steel used in the deep oil industry that could be applied in the fabrication of microsensors and microactuators. However, there are no previous studies that could estimate cutting forces, no information in the literature about specific cutting force values for super duplex nor for similar stainless steels in micromilling. The present article analyzes three stainless steels and their behavior during micromilling: super duplex, which is a dual phase material, an austenitic and a ferritic stainless steel, chosen with similar mechanical properties to each phase of the first one. A set of experiments explored different feeds per tooth, as it is an important factor to identify mechanical behavior in micro scale, and cutting speed in order to develop a mechanistic force approach. The results showed that force coefficients for the dual phase material are located between the values of the austenitic and ferritic steels, indicating that heterogeneous super duplex steel microstructure can be modeled as a combination of ferritic and austenitic stainless steel coefficients. Lower feed per tooth experiments presented higher fluctuation of the maximum peak forces, maintaining average forces inside the predicted range.