Tribological behavior of cutting tool in high-speed machining of aluminum-silicon alloys

An analysis of the mechanism of cutting tool wear in high speed machining of cast aluminum alloys is conducted in this research work. The results of this analysis indicate that the interaction between the hard silicon constituencies of the alloy and the surface of the cutting tool is the most detrimental to tool life. The wear of the cutting tool in such interactions, governed by fatigue wear mechanism, is directly proportional to the silicon content of the alloy, to the silicon grain size, and to the tool's loading conditions.; In order to predict the tool wear in machining aluminum-silicon alloys, a new wear model is developed. The fracture mechanics approach in wear rate estimation is implemented in this model. As an input data for the tool wear modeling, the normal and tangential stresses acting on the flank of the cutting tool is used. These stresses are predicted from the mechanistic model developed in the current research work. This model determines the stresses acting on the flank of the cutting tool by subtracting the cutting forces that act on the perfectly sharp cutting tool from the total forces of the worn cutter. The determined stresses are used in the fracture mechanics analysis of the cracks propagation in the cobalt binder of cemented carbides cutting tool.; The fracture mechanics analysis in this research work is performed using the finite element model of the tool-workpiece sliding contact. The real microstructure of the cutting tool is incorporated in the finite element model of tool-workpiece contact, and elastic-plastic properties of cobalt, and are defined by continuum theory of crystal plasticity are introduced in the model by UMAT subroutine of the ABAQUSRTM finite element software.; The crack propagation rate, determined from finite element modeling, is integrated with an analytical model of cutting tool wear, developed in this research. This model is able to predict the wear rate of the cutting tool, base on the microstructural characteristics of the cutting tool and workpiece material, as well as the tool's loading conditions. The analytical model is calibrated for the particular set of cutting conditions. A systematic model calibration procedure is developed, and the experimental results are presented for the calibration procedure. Model verification tests are conducted in wide range of cutting conditions. These tests demonstrate that the predicted tool wear is within 2.4% of the experimentally measured wear.; A series of actions is proposed that will decrease the tool wear in high speed machining of aluminum-silicon alloys. These actions include the application of a Minimum Quantity of Lubricant (MQL) technology and diamond coating in milling operations. As experimental results have shown, the lubricant applied to the cutting zone efficiently protects the surface of cutting tool. The wear suppressing ability of MQL lubricants, evaluated in the cutting tests, is in the range 1.2--4.5. The performance of the polycrystalline diamond layer, deposited on the surface of cutting tool, is also evaluated in the cutting tests. The results of the evaluation have shown that the diamond coating provided an excellent tool wear protecting ability, but failed catastrophically with the total detachment of deposited films from the carbide substrate. It is concluded in this research that the optimization of the thickness of diamond layer is required.