Creating Surface Morphologies by Cryogenic Machining

Cryogenic machining offers the potential to improve the surface morphology within a single process step by substituting the surface hardening into the form-shaping process. To realize a sufficient surface hardening, low temperatures and high mechanical loads have to be provided by the cryogenic machining process. Within this chapter, facilities and processes are presented aiming to optimize the surface morphology via cryogenic turning and milling. Cryogenic cooling strategies aim to achieve the necessary low thermal loads. The thermal loads are characterized via cutting experiments and temperature field simulations. The machining operations are designed in terms of cutting parameters and tool properties to provide favorable thermo-mechanical loads and consequently an optimized surface morphology. For both a metastable austenitic steel and a difficult-to-cut titanium alloy, an optimization of the surface morphology is realized. In addition, a novel, sub-zero cooling approach is presented and compared with the application of cryogenic coolants and conventional cooling approaches.