Investigation of MQL-Employed Hard-Milling Process of S60C Steel Using Coated-Cermented Carbide Tools

The application of cutting fluids in machining brings out many benefits, but their use is accompanied by health and enviroment hazards. MQL （Minimum Quantity Lubricant） has become a preciously alternative solution for lubrication against dry machinning and flood cooling lubricant, and this is a step toward green machining. This paper presents a comprehensively experiemental study on investigation of MQL performance in hard milling of S60C steel for multiple responses, including surface quality, cutting forces and tool wear. Compared to dry milling, even-enhanced surfaces finish quality, 20% less cutting force （Ft） and almost 112% prolonged tool lifetime are achieved by using MQL with 5% Emulsion in hard milling. In addition, this study compared the performances of MQL milling by using 5% Emulsion to the peanut oil completely harmless to the enviroment. This encouraging result, therefore, reveals that the MQL-employed hard milling can enable significant improvement in productivity, product quality, and overall machining economy even after covering the additional cost of designing and implementing MQL system. Moreover, this study also shows the limitation of peanut oils employed in MQL and proposes the further research in novel additives to enhance the performance of cooling lubricant for vegetable oils.

Effects of the deep rolling process on the surface roughness and properties of an Al-3vol%SiC nanoparticle nanocomposite fabricated by mechanical milling and hot extrusion

Deep rolling is one of the most widely used surface mechanical treatments among several methods used to generate compressive residual stress. This process is usually used for axisymmetric components and can lead to improvements of the surface quality, dimensional accuracy, and mechanical properties. In this study, we deduced the appropriate deep rolling parameters for Al-3vol%Si C nanocomposite samples using roughness and microhardness measurements. The nanocomposite samples were fabricated using a combination of mechanical milling, cold pressing, and hot extrusion techniques. Density measurements indicated acceptable densification of the samples, with no porosity. The results of tensile tests showed that the samples are sufficiently strong for the deep rolling process and also indicated near 50% improvement of tensile strength after incorporating Si C nanoparticle reinforcements. The effects of some important rolling parameters, including the penetration depth, rotation speed, feed rate, and the number of passes, on the surface quality and microhardness were also investigated. The results demonstrated that decreasing the feed rate and increasing the number of passes can lead to greater surface hardness and lower surface roughness.

Microstructure investigation of dynamic recrystallization in hard machining:From thermodynamic irreversibility perspective

The drastically changed thermal,mechanical,and chemical energies within the machined surface layer during hard machining tend to initiate microstructural alteration.In this paper,attention is paid to the introduction of thermodynamic potential to unravel the mechanism of microstructure evolution.First,the thermodynamic potential-based model expressed by the Helmholtz free energy was proposed for predicting the microstructure changes of serrated chip and the machined surface layer.Second,the proposed model was implemented into a validated finite element simulation model for cutting operation as a user-defined subroutine.In addition,the predicted irreversible thermodynamic state change in the deformation zones associated with grain size,which was reduced to less than 1 mm from the initial size of 1.5 mm on the machined surface,was provided for an in-depth explanation.The good consistency between the simulated results and experimental data validated the efficacy of the developed model.This research helps to provide further insight into the microstructure alteration during metal cutting.