Characterization of Wear Modes in Orthogonal Milling of 15-5PH Stainless Steel

Tool wear remains of high interest for industry, as it influences process costs and part’s surface integrity. Although experimental and analytical investigations have been the main ways to investigate wear, the growing development of computational power enables predicting tool wear based on chip formation simulations. If this has been quite successful in turning, developments in milling are still limited due to the specific nature of this machining operation characterized by an interrupted cutting process leading to mechanical and thermal cyclic loadings onto the cutting tool. Wear modes are often not well characterized and become even more difficult to model as far as hard to machine material such as martensitic stainless steels are concerned. The present work propose to investigate wear in orthogonal milling of a 15-5PH martensitic stainless steel. An experimental campaign is first performed to identify the wear modes when cutting this material with uncoated and coated carbide tools. Milling forces, tool wear and material transfer are especially studied. A multi-scale numerical procedure is then developed by combining an Arbitrary-Lagrangian-Eulerian (ALE) thermomechanical model to a pure thermal sub-model in order to predict the thermomechanical loadings withstood by the tool. The thermal sub-model is applied at the scale of the coating in order to extract the thermal gradients generated by the interrupted cutting. These loadings are finally compared to the reported wear modes to identify a correlation and improve their understanding.

Investigations on book cutting by circular knife with eccentric blade movement

The paper describes investigations on new method of the book cutting by using special circular knife with eccentric blade movement. Analysis of kinematic parameters of book block cutting shows, that by using eccentric circular cutting knife the cutting process may be realized in two different modes: continuous cutting – with the constant contact between cutting edge and cut material, and interrupted cutting process - with the impulse cutting knife action to treated material. The results of the conducted experimental studies confirm the kinematic analysis of the cutting process.

An Investigation of the Work Hardening Behavior in Interrupted Cutting Inconel 718 under Cryogenic Conditions

The severe work hardening phenomenon generated in the machining of Inconel 718 is harmful to continue cutting processes, while being good for the component’s service performance. This paper investigates the performance of cryogenic assisted machining used in the cutting processes, which can reduce the waste of fluids. The influence of dry and cryogenic machining conditions with different cutting speeds on the work hardening layer is investigated based on the interrupted cutting of Inconel 718. Cutting temperature distribution obtained from simulations under different conditions is used to discuss the potential mechanism of work hardening. Then, the depth of work hardening and degree of work hardening (DWH) are investigated to analyze the surface deformation behavior, which strengthens the machined surface during metal cutting processes. From the cutting experiments, the depth of the work hardening layer can reach more than 60 μm under the given cutting conditions. In addition, a deeper zone can be obtained by the cooling of liquid nitrogen, which may potentially enhance the wear performance of the component. The results obtained from this work can be utilized to effectively control the work hardening layer beneath the surface, which can be applied to improve the service performance.