The effect of various gadolinium contents on the number density and morphology of sulfide in Al-killed high-sulfur steel was investigated. Meanwhile, the effect of characterization of sulfide ...inclusions, i.e., number density and morphology on the cutting performance of steel also were studied. The evolution process of sulfide inclusions with the increasing T.Gd content from 0 ppm to 198 ppm in steel samples could be described as follows: MnS → (Gd-O-S)-MnS→(Gd-S)-MnS →Gd-S. As the gadolinium content in the steel increased, sulfide inclusions with an aspect ratio of < 3 increased from 26.1 % to 99.7 % and the number density of sulfides decreased from 438 #/mm2 to 80.4 #/mm2. Spherical sulfides could form micro-holes during cutting, facilitating the chip-breaking process, whereas long-strip MnS tended to self-break during cutting. The higher the proportion of C-type chips in the cutting process, the better the cutting performance of the material. Therefore, spherical sulfides exhibited superior modification effects on surface finishes compared to long-strip sulfides. In low-speed cutting, sulfide morphology predominantly affected surface roughness, while in high-speed cutting, the number density of sulfides became the dominant factor. The addition of gadolinium can effectively decrease the surface roughness of the material at various cutting parameters. Moreover, the Gd-O film can be formed on the tool surface was observed after the addition of gadolinium in the steel, which can increase the lubrication during the cutting process and reduce the tool surface wear.
•Novel heavy rare earth gadolinium for modifying MnS inclusion and enhancing cutting performance of material was proposed.•The mechanism of spherical sulfides was more favorable for improving the cutting properties of the steel was elucidated.•The morphology and number density of sulfide had various effects on the surface roughness at different cutting parameters.•The Gd-O film was observed on the tool surface, which reduced the tool surface wear.
This paper presents an overview of the recent advances in high performance cutting of aerospace alloys and composite currently used in aeroengine and aerostructure applications. Progress in cutting ...tool development and its effect on tool wear and surface integrity characteristics of difficult to machine materials such as nickel based alloys, titanium and composites is presented. Further, advances in cutting technologies are discussed, focusing on the role of hybrid machining processes and cooling strategies (MQL, high pressure coolant, cryogenic) on machining performance. Finally, industrial perspectives are provided in the context of machining specific components where future challenges are discussed.
•Provides a new approach for determining the machinability aspects of Inconel 718.•Understanding of the mechanisms created by the milling process of Inconel 718 in dry and MQL environments was ...achieved.•Experimental and predicted data were compared with the machine learning method.•The machine learning method was found to be applicable in machinability experiments.•Considering the machinability properties in milling, it has been determined that the MQL process is effective.
Inconel 718 super alloy, which is widely used in the aerospace industry, has a high fracture resistance, and withstand to high temperatures. The alloy contains mainly Nickel, Chromium and Molybdenum elements in its chemical composition put it among difficult to cut materials. In this context, this study aims to improve the machinability of Inconel 718 superalloy by examining the effect of dry and MQL machining environments while measuring machinability indicators during milling. Tribological aspects considered since the wear, friction and lubrication behavior have a dramatic impact on responses such as tool wear, surface integrity and chip morphology. Microstructural and graphical results were assessed in terms of varying levels of cutting parameters and lubrication conditions. Comparison analysis between MQL and dry media indicated that MQL produces better surface topography and chip morphology, longer tool life in addition to improvement on surface roughness (up to 23.7 %) and cutting temperatures (up to 27.4 %). The root mean square error (RMSE) and coefficient of determination (R2) metrics were utilized to evaluate the findings in the course of machine learning. According to the mean and 95 % confidence interval of RMSE, error rates were found to be good and R2 varied between 67 % and 98 %. Predicted results are in a good agreement with the experimental data which indicated the applicability of machine learning algorithms on sustainable methods of machining.
Carbon fibre reinforced polymer (CFRP) composites have excellent specific mechanical properties, these materials are therefore widely used in high-tech industries like the automobile and aerospace ...sectors. The mechanical machining of CFRP composites is often necessary to meet dimensional or assembly-related requirements; however, the machining of these materials is difficult. In an attempt to explore this issue, the main objective of the present paper is to review those advanced cutting tools and technologies that are used for drilling carbon fibre reinforced polymer composites. In this context, this paper gives a detailed review and discussion of the following: (i) the machinability of CFRP including chip removal mechanisms, cutting force, tool wear, surface roughness, delamination and the characteristics of uncut fibres; (ii) cutting tool requirements for CFRP machining; and (iii) recent industrial solutions: advanced edge geometries of cutting tools, coatings and technologies. In conclusion, it can be stated that advanced geometry cutting tools are often necessary in order to effectively and appropriately machine required quality features when working with CFRP composites.
Calcium fluoride (CaF2) optical components are produced by ultra-precision machining, but the often-neglected ambient water may potentially affect its processing. This work provides a systematic ...study on the role of water in the machinability of single-crystal CaF2. Micro-scratching experiments revealed poor machinability and reduced deformability under water adsorption. Atomic scratching simulations reproduced the mechanical deformation and identified the enhancement in dislocation nucleation with water, which led to the reduction in deformability due to dense cross-linking of dislocations. Atomic scale cutting simulations also identified easier formation of subsurface cracks under water adsorption. With the aid of mechanical schematic models based on the simplification of the scratching process, this work revealed that while water enhances the plastic flow of the material during machining, the accumulation of dislocations creates stress conditions sufficient to induce material fracture, which is a unique influence of water adsorption on the reduction in machinability of CaF2.
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Effective heat removal from cutting zone is expected to ensure favorable machinability. In this context, turning of Ti-6Al-4V (grade 5) has been conducted under the implementation of ...two thin jets of pressurized coolant; one jet was aimed at the chip-tool interface whereas another jet was directed towards the tool-work interface. Afterward, the effects of duplex coolant jets on chip-tool interface temperature were studied. Furthermore, as part of machinability investigation the mean surface roughness, cutting force, tool wear and chip formation have been analyzed at varying cutting speed and feed rate combinations. The most dominant wear mechanisms, revealed by scanning electron microscopic images were, in dry cutting the adhesion and rubbing, and in HPC-assisted turning the crater wear and flank wear. The enhanced heat dissipation by double jets is accredited as the primary reason for the reduction of cutting forces, surface roughness and tool wear.
The green improvement of manufacturing high-temperature martensitic alloy steel using minimum quantity lubrication (MQL) involves an MQL device and a scientific method to assess the efficacy of the ...device application. This paper proposed a weight-variable machinability evaluation model based on multivariate heterogeneous data to compare the MQL process with the conventional machining lubrication processes. The proposed model comprises experimental-based intuitive evaluation and numerical machinability index (MI). The assessment model considers a multi-indicator and time-quality-cost-resource-environment (TQCRE) system. The MI is based on static-dynamic proximity, which is calculated according to indicator weights for subjective–objective combinations. The model was applied to a novel MQL system developed for manufacturing high-temperature martensitic alloys by performing milling experiments under four lubrication conditions. Experimental intuitive data indicated the superior feasibility of the MQL device, that is, the developed MQL method enhanced machining efficiency, ensured good machining quality, reduced tool wear by 17%, and cut forces by 7–14%. Moreover, the MQL process achieved the maximum machinability index regardless of the priority allocated to any indicator of machining quality, time, cost, resource loss, and environmental pollution. There was no degradation in machining via MQL under different environments, which validates the feasibility of the field application of the MQL method. The result is consistent with the experimental intuitive assessment, confirming the reasonableness and practical ability of the mathematical assessment model. This study may be considered as further validation of the multi-indicator machinability assessment for the green lubrication process. Future research on more cases might extend the explanations of the stability and hidden factors of the developed model.
