Tool Wear Mechanisms In Machining Research Articles

Thermodynamic modeling framework for prediction of tool wear and tool protection phenomena in machining

Chemical, oxidational and diffusional interactions between the tool, chip and cutting environment are known tool wear mechanisms in machining. However, the interaction between tool, coating, workpiece, coolant and atmospheric oxygen can, under favorable conditions, lead to formation of reaction products that retard tool wear. A method with the ability to predict theses interactions, would therefore enable a better control over tool life in machining. An attempt to create such a modelling framework is developed in this study. This method can predict the phase composition and the driving force for degradation and the formation of protective interaction products in the cutting zone. This modeling approach is applicable across cutting processes in which chemical, diffusional and oxidational wear are dominant or present. This framework has been applied to investigate the interactions occurring in the cutting zone during turning of a medium alloyed low-carbon steel (Hybrid Steel® 55). A range of degradation events are predicted, as well as the formation of a protective corundum (Al,Fe,Cr)2O3 or spinel (Al,Fe,Cr)3O4 film due to an interaction between the Al-alloyed steel and the environment. Validation of the modeling was performed by studying tool wear and reaction products formed when machining with ceramics, PcBN and coated carbide tooling. Inserts are studied by the use of scanning and transmission electron microscopy, after cutting tests were performed. Additional tests were performed in different environments (dry, argon and coolant). The results confirmed the model predictions of oxidation and diffusion wear as well as the formation of an (Al,Fe,Cr)3O4 tool protection layer. Thus, the proposed thermodynamic framework seem promising to serve as a predictive instrument for the correct pairing of existing tool and workpiece combinations and cutting parameters, or for tailoring respective material compositions for intentional formation of a tool protection layer. As well as guidance on how to apply present and future kinetic models when concurrent interaction mechanisms are present. Which lead to a reduction and minimization of costly experimental machining tests.

Study of the Tool Wear Process in the Dry Turning of Al–Cu Alloy

Light alloy machining is a widely implemented process that is usually used in the presence of cutting fluids to reduce wear and increase tool life. The use of coolants during machining presents negative environmental impacts, which has increased interest in reducing and even eliminating their use. In order to obtain ecofriendly machining processes, it will be necessary to suppress the use of cutting fluids, in a trend called “dry machining”. This fact forces machines to work under aggressive cutting conditions, producing adhesion wear that affects the integrity of the parts’ surfaces. This study describes cutting tool wear mechanisms in machining of UNS A92024 samples under dry cutting conditions. Energy dispersive spectroscopy (EDS) analysis shows the different compositions of the adhered layers. Roughness is also positively affected by the change of the cutting geometry produced in the tool.

Investigating tool wear mechanisms in machining of Ti-6Al-4V in flood coolant, dry and MQL conditions

The objective of this study is to identify and explain tool wear mechanisms that dominate during machining of titanium alloy Ti-6Al-4V in dry, flood coolant, and minimum quantity lubrication (MQL) conditions. A series of experiments were conducted using end milling of Ti-6Al-4V by varying feed rate and depth of cut, while the cutting speed was kept constant at comparatively higher cutting speed. Both uncoated and titanium aluminum nitride (TiAlN)-coated carbide tools were used for machining Ti-6Al-4V at the same settings of parameters. It was observed that abrasion was the most dominant tool wear mechanism for all dry, flood coolant and MQL machining conditions. Edge chipping and tool nose wear were the next dominating tool wear mechanisms in conventional flood coolant machining, which may be associated with the thermal fatigue caused by the periodic cooling of tool tip from the high temperature generated during machining. On the other hand, adhesion was the second most dominant tool wear mechanism in the dry machining. Both the edge chipping and adhesion of chips to the cutting tools were reduced significantly in MQL machining. The delamination of coating film was observed when TiAlN-coated carbide tools were used for machining Ti-6Al-4V. The delamination was more significant in wet and MQL machining compared to dry machining, indicating the effectiveness of coated tools in dry machining condition compared to wet and MQL machining conditions. Among three conditions, MQL provided the least occurrences of tool wear, indicating suitability of MQL in productive machining of titanium alloys.

Effect of HIP parameters on surface integrity of machined HIP workpieces

Hot isostatic pressing (HIP) materials with five relative densities of 99.8%, 99.4 %, 98.8%, 97.0% and 95.04% were prepared by HIP technology with five parameters and machined with coated cemented tool. Progressions of surface integrity of the machined HIP materials versus HIP parameter were studied. Heat conductivities, microstructures and mechanical properties of the HIP workpieces were varied, mainly because of the different pressing temperatures and pressing pressures. Chip-tool wear mechanisms also were changed with the HIP parameters due to the micro-voids of the workpieces. The phenomenon that the changing trends of the HIP workpiece surface integrities with cutting speed were not completely similar resulted from the varied thermodynamic properties and the different tool wear mechanisms in machining of the HIP materials.

Analysis of Element Diffusion between Alloy Cast Iron and WC/Co Cemented Carbides

An alloy cast iron has special properties by adding some alloying elements to the ordinary cast iron ASTMNo35A. Diffusion wear is one of the main cutting tool wear mechanisms in machining of the alloy cast irons. The diffusion of tungsten (W) and iron (Fe) between the alloy cast iron and the WC/Co cemented carbides was investigated in this paper by means of heating diffusion couple. It has be proved from the experiment that Fe in the alloy cast iron diffused a deeper distance in the WC/Co cemented carbides with the higher Co content; while the diffusion of W element in the WC/Co cemented carbides the alloy cast iron was not serious. The Vickers-hardness analysis of the alloy cast iron and K20 cemented carbide couple was determined. The elements diffusion impaired the hardness of the alloy cast iron and WC/Co cemented carbide cutting tool.

Tool wear mechanisms in machining of three titanium alloys with increasing β-phase fraction

Mechanical and microstructural properties of titanium alloys change with β-phase fraction. This in turn influences the dominant tool wear mechanisms in their machining. This work therefore involves turning experimentation on three titanium alloys with varying β-phase fraction, namely, α, α+ β and β-rich alloys using coated carbide tools, to identify dominant wear mechanisms, which hitherto have not been adequately investigated. The dominant wear mechanisms were investigated using scanning electron microscopy and energy-dispersive X-ray analysis of worn tool surfaces and were also correlated with the cutting forces during machining. Abrasion, abrasion with built-up edge and plastic deformation of cutting edge appeared to be the dominant tool wear mechanisms in α, α+ β and β-rich alloy, respectively. At the same time, diffusion of Sn, V and Mo from α, α+ β and β-rich alloys to tool face, respectively, was observed. The chip–tool contact length predicted using the analytical models from the literature matched closely with the experimental values.

Experimental study of high-speed milling of SiCp/Al composites with PCD tools

In this paper, high-speed milling experiments on silicon carbide particle reinforced aluminum matrix (SiCp/Al) composites with higher volume fraction and larger particles were carried out using polycrystalline diamond (PCD) tools at dry and wet machining conditions. For comparison, a TiC-based cermet tool was also used in milling the same workpiece material at very low speed. Worn PCD and cermet tools were measured and extensively characterized by scanning electron microscopy at different machining conditions. Furthermore, the effect of cutting distance on milling force and surface roughness were also investigated. The results showed that the main tool wear mechanism in machining of this type of material was abrasion on the flank face, and it was verified that the TiC-based cermet tool was not suitable for machining SiCp/Al composites with higher volume fraction and larger particles due to the heavy abrasive nature of reinforcement.

The Investigation of Tool Wear in Metal Machining Using Finite Element Method

The existing studies based on 2-dimension cutting model are partial investigations on tool wear. In order to get close to the true cutting conditions, the Lagrangian thermo-viscoplastic cutting simulations were conducted and the tool wears were predicted under different cutting speeds using 3-dimension finite element models. The simulation results indicate that when the cutting speed increases the cutting forces will reduce accordingly while the wear depth will be deeper. As a result, different factors should be considered at the same time when the speed range is selected. This study has shown that the finite element method is a valuable approach to understand the tool wear mechanism in machining and the influences of different cutting speeds.

Tool wear mechanisms in machining

Most of tool wear studies are classified as empirical (e.g. Taylor's equation); thus, they do not bring out the physical nature of the wear phenomenon. Consequently, tool life in general cannot be predicted by extending the result from one study. By understanding the physics behind the process, the important wear mechanisms can be identified. By constructing a wear model for each wear mechanism with more fundamental quantities such as materials properties, these models can be combined and extended to estimate tool life. This should be the ultimate goal of tool wear research in machining. However, a major gap exists between the current understandings of tool wear and the ultimate goal of tool wear research. This paper will describe how cutting tools are being worn down during machining based on the physics behind tool wear.

Ultraprecision Cutting of Glass BK7

The development of the capability to machine glass materials to optical quality is highly desirable. In this work, the deformation characteristics of brittle materials were analyzed by micro and nano indentations. Diamond cutting of optical glass BK7 was performed in order to investigate the tool wear mechanism in machining of brittle materials and the effect of tool vibration on material removal mechanism. The tool wear mechanism was discussed on the basis of the observation of wear zone. Ductile-mode cutting has easily been achieved with the application of ultrasonic vibration during cutting of glass. It was confirmed experimentally that the tool wear and surface finish were improved significantly by applying ultrasonic vibration to the cutting tool.