scholarly journals Multilayer Diamond Coatings Applied to Micro-End-Milling of Cemented Carbide

Materials ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3333
Author(s):  
Eduardo L. Silva ◽  
Sérgio Pratas ◽  
Miguel A. Neto ◽  
Cristina M. Fernandes ◽  
Daniel Figueiredo ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
End Milling ◽  
Interfacial Stress ◽  
Cemented Carbide ◽  
Air Cooling ◽  
Micro Machining ◽  
Diamond Coatings ◽  
Wear Properties ◽  
High Adhesion ◽  
Micro End Milling

Cobalt-cemented carbide micro-end mills were coated with diamond grown by chemical vapor deposition (CVD), with the purpose of micro-machining cemented carbides. The diamond coatings were designed with a multilayer architecture, alternating between sub-microcrystalline and nanocrystalline diamond layers. The structure of the coatings was studied by transmission electron microscopy. High adhesion to the chemically pre-treated WC-7Co tool substrates was observed by Rockwell C indentation, with the diamond coatings withstanding a critical load of 1250 N. The coated tools were tested for micro-end-milling of WC-15Co under air-cooling conditions, being able to cut more than 6500 m over a period of 120 min, after which a flank wear of 47.8 μm was attained. The machining performance and wear behavior of the micro-cutters was studied by scanning electron microscopy and energy-dispersive X-ray spectroscopy. Crystallographic analysis through cross-sectional selected area electron diffraction patterns, along with characterization in dark-field and HRTEM modes, provided a possible correlation between interfacial stress relaxation and wear properties of the coatings. Overall, this work demonstrates that high adhesion of diamond coatings can be achieved by proper combination of chemical attack and coating architecture. By preventing catastrophic delamination, multilayer CVD diamond coatings are central towards the enhancement of the wear properties and mechanical robustness of carbide tools used for micro-machining of ultra-hard materials.

Modeling of burr thickness in micro-end milling of Ti6Al4V

2018 ◽  
Vol 233 (4) ◽  
pp. 1087-1102 ◽  
Author(s):  
Vipindas Kizhakken ◽  
Jose Mathew
Keyword(s):  
Mathematical Model ◽  
Prediction Error ◽  
End Milling ◽  
Value Added ◽  
Material Model ◽  
Machining Process ◽  
Micro Machining ◽  
Proposed Model ◽  
Wide Range ◽  
Micro End Milling

Mechanical micro-machining of Ti6Al4V is finding great demand because of its wide range of application in various fields such as communication, optics and biomedical devices. Increasing demands on functioning and performance requires components to be free from burrs after the machining process. Presence of burrs on micro-mechanical parts or features significantly affects quality and proper assembly of the parts. Also in micro-machining, the size of burr is comparable to that of micro-features. Since the formation of burr is inevitable in any machining process, generally the deburring operation is performed to remove burrs. Burr thickness is one of the important parameters which describe the time and method necessary for the deburring operation. Burrs on micro-parts are generally characterized using scanning electron microscope, which is a time-consuming, costly and non-value-added activity. However, a proper mathematical model will help predict burr thickness easily. In this article, a mathematical model to predict burr thickness during micro-end milling of Ti6Al4V is presented. The proposed model was developed based on the principle of continuity of work at the transition from chip formation to burr formation. Ti6Al4V titanium alloy is one of the materials which generates segmented (saw-tooth) chips at low cutting speeds. Hence, initially an appropriate material constitutive model was selected based on better prediction of burr thickness. Then, to reduce the prediction error, machining temperature was evaluated for all experimental conditions and included in the model. From the initial study, it was found that Hyperbolic TANgent material model gives a better prediction compared to Johnson–Cook material model. Later, after including machining temperature into the model it was observed that the prediction error was reduced. The proposed model was validated with the experimental results.

scholarly journals Fabrication and characterization of resistive double square loop arrays for ultra-wide bandwidth microwave absorption

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Ji-Young Jeong ◽  
Je-Ryung Lee ◽  
Hyeonjin Park ◽  
Joonkyo Jung ◽  
Doo-Sun Choi ◽  
...  
Keyword(s):  
Sheet Resistance ◽  
Manufacturing Process ◽  
End Milling ◽  
Milling Process ◽  
Wide Bandwidth ◽  
Machined Surface ◽  
Array Pattern ◽  
Micro End Milling ◽  
Array Structures ◽  
Printing Processes

AbstractMicrowave absorbers using conductive ink are generally fabricated by printing an array pattern on a substrate to generate electromagnetic fields. However, screen printing processes are difficult to vary the sheet resistance values for different regions of the pattern on the same layer, because the printing process deposits materials at the same height over the entire surface of substrate. In this study, a promising manufacturing process was suggested for engraved resistive double square loop arrays with ultra-wide bandwidth microwave. The developed manufacturing process consists of a micro-end-milling, inking, and planing processes. A 144-number of double square loop array was precisely machined on a polymethyl methacrylate workpiece with the micro-end-milling process. After engraving array structures, the machined surface was completely covered with the developed conductive carbon ink with a sheet resistance of 15 Ω/sq. It was cured at room temperature. Excluding the ink that filled the machined double square loop array, overflowed ink was removed with the planing process to achieve full filled and isolated resistive array patterns. The fabricated microwave absorber showed a small radar cross-section with reflectance less than − 10 dB in the frequency band range of 8.0–14.6 GHz.

scholarly journals Optimisation of Mechanical Properties of Gradient Zr–C Coatings

Materials ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 296
Author(s):  
Łukasz Szparaga ◽  
Przemysław Bartosik ◽  
Adam Gilewicz ◽  
Katarzyna Mydłowska ◽  
Jerzy Ratajski
Keyword(s):  
Adhesive Layer ◽  
Scratch Test ◽  
Deposition Process ◽  
Functionally Graded ◽  
Wear Properties ◽  
Mechanical And Tribological Properties ◽  
High Adhesion ◽  
Graded Material ◽  
Residual Stresses And Strains ◽  
Optimisation Procedure

One of the key components of the designing procedure of a structure of hard anti-wear coatings deposited via Physical Vapour Deposition (PVD) is the analysis of the stress and strain distributions in the substrate/coating systems, initiated during the deposition process and by external mechanical loads. Knowledge of residual stress development is crucial due to their significant influence on the mechanical and tribological properties of such layer systems. The main goal of the work is to find the optimal functionally graded material (FGM) coating’s structure, composed of three functional layers: (1) adhesive layer, providing high adhesion of the coating to the substrate, (2) gradient load support and crack deflection layer, improving hardness and enhancing fracture toughness, (3) wear-resistant top layer, reducing wear. In the optimisation procedure of the coating’s structure, seven decision criteria basing on the state of residual stresses and strains in the substrate/coating system were proposed. Using finite element simulations and postulated criteria, the thickness and composition gradients of the transition layer in FGM coating were determined. In order to verify the proposed optimisation procedure, Zr-C coatings with different spatial distribution of carbon concentration were produced by the Reactive Magnetron Sputtering PVD (RMS PVD) method and their anti-wear properties were assessed by scratch test and ball-on-disc tribological test.

Prediction of Burr Formation in Fabricating MEMS Components by Micro End Milling

2009 ◽  
Vol 74 ◽  
pp. 247-250 ◽  
Author(s):  
Mohammad Yeakub Ali ◽  
Mohd Aliff Omar ◽  
Khairul Irman Othman ◽  
Wayne N.P. Hung
Keyword(s):  
End Milling ◽  
Cutting Speed ◽  
304 Stainless Steel ◽  
Burr Formation ◽  
Aisi 304 ◽  
Burr Height ◽  
Milling Parameters ◽  
Milling Tool ◽  
Micro End Milling ◽  
Chip Load

This paper discusses burr formation in micromilling of AISI 304 stainless steel. Chip load, cutting speed and the application of coolant were chosen as the milling parameters. Experiments were conducted using 500 µm diameter tungsten carbide end milling tool. Milling parameters and measured burr height values were analyzed and statistical models were developed for the estimation of burr height. The models showed that the chip load and cutting speed both have direct and interactive contribution to burr formation. When micromachining without coolant, the burr height increases about 40% compared to that of machining with coolant. The optimized values of chip load and cutting speed were found to be 1 µm/tooth and 78 mms-1 respectively. The predicted burr heights were 5-7% larger than that of measured values.

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