Reviewing Performance Measures of the Die-Sinking Electrical Discharge Machining Process: Challenges and Future Scopes.

The most well-known and widely used non-traditional manufacturing method is electrical discharge machining (EDM). It is well-known for its ability to cut rigid materials and high-temperature alloys that are difficult to machine with traditional methods. The significant challenges encountered in EDM are high tool wear rate, low material removal rate, and high surface roughness caused by the continuous electric spark generated between the tool and the workpiece. Researchers have reported using a variety of approaches to overcome this challenge, such as combining the die-sinking EDM process with cryogenic treatment, cryogenic cooling, powder-mixed processing, ultrasonic assistance, and other methods. This paper examines the results of these association techniques on various performance measures, such as material removal rate (MRR), tool wear rate (TWR), surface roughness, surface integrity, and recast layer formed during machining, and identifies potential gap areas and proposes a solution. The manuscript is useful for improving performance and introducing new resolutions to the field of EDM machining.

Studies on Mechanical, Biocompatibility and Antibacterial Activity of Plasma Sprayed Nano/Micron Ceramic Bilayered Coatings on Ti-6Al-4V Alloy for Biomedical Application.

Ceramic oxides such as alumina and zirconia are used to fabricate dental and orthopedic implants. However, their usage is limited as they fail due to low fracture toughness. To overcome this issue, ceramic coatings on metallic implants is attempted to have a combined effect of ceramics and metallic materials. This paper reports on the microstructure, phase analysis, mechanical properties, osseointegration and antibacterial activity of three different wear-resistant coatings developed on Ti-6Al-4V alloy which is used widely as orthopedic and dental implants. The powders of following compositions, i. Nanostructured Al2O3 + 13 wt% TiO2/µ-TiO2 BL coating (S1), ii. µ-Al2O3 + 13 wt% nanostructured TiO2/µ-TiO2 BL coating (S2), iii. Nanostructured Al2O3 + 13 wt% TiO2/µ-YSZ BL coating (S3), were sprayed using atmospheric plasma spray process onto Ti-6Al-4V alloy. The coatings were characterized using X-ray diffraction (XRD), Scanning electron microscope (SEM), Profilometer and gonieometer to determine their phases, microstructure, surface roughness and contact angle. In addition, micro indentation hardness and scratch resistance were also evaluated. Amongst the three coatings, S2 exhibited higher hardness value with higher scratch resistance. The antibacterial activity was studied using colony formation on all three coatings. The antibacterial efficiency of S1 as well as S3 coatings was higher as seen from less number of bacterial colonies on the surface. The results of in-vitro studies on the biocompatibility of nano/micron alumina and zirconia ceramic coatings which were analyzed with hMSC's, reveals that S1 is cytotoxic with less number of cell attachment when compared to S2 and S3.

Evaluation of the nanostructure of cervical third cementum in health and chronic periodontitis: An in vitro study.

BACKGROUND: During the progression of periodontal disease, the cementum undergoes alterations in its structure and composition. Understanding the nanostructure of cementum, in terms of its mechanical properties, will provide an insight into the milieu that periodontal ligament cells encounter in health and chronic periodontitis. This study aims to analyze the nanomechanical properties of the cervical third of the cementum (transverse section) in health and chronic periodontitis. MATERIALS AND METHODS: Twenty teeth (10 healthy and 10 periodontally diseased) were collected and the nanomechanical properties of the transverse section of the cervical third cementum were evaluated with depth-sensing nanoindentation technique under dry conditions. A total of 100 nanoindentations were performed to analyze the modulus of elasticity and hardness of cervical third of the cementum. RESULTS: The nanomechanical properties of the healthy cervical third cementum sections were significantly higher (P < 0.05) (hardness: 0.720 ± 0.305 GPa; modulus: 15.420 ± 3.902 GPa) than the diseased cementum section (hardness: 0.422 ± 0.157 GPa; modulus: 11.056 ± 3.434 GPa). CONCLUSION: The results of our study indicate that the hardness and modulus of elasticity of the cervical third cementum decreases significantly in chronic periodontitis.

Nanomechanical and optical properties of yttrium thin films by magnetron sputtering.

This Letter reports on nanomechanical and optical properties of yttrium thin films deposited on an Si (100) wafer. Elemental depth profiling by a secondary ion mass spectrometer revealed absence of formation of yttrium hydride, both on the surface and beneath. The optical properties were investigated by spectroscopic ellipsometry, and the refractive indices extracted after suitable modeling were found to be 2.51 at 546 nm. Hardness and elastic modulus of these films were found to be 7 and 142 GPa, respectively. These studies indicate that yttrium thin films are suitable for x-ray mirrors, photocathode emitters in e-beam lithography, electron microscopes, and free-electron lasers.

Improvement in tribological properties by modification of grain boundary and microstructure of ultrananocrystalline diamond films.

Grain boundaries and microstructures of ultrananocrystalline diamond (UNCD) films are engineered at nanoscale by controlling the substrate temperature (TS) and/or by introducing H2 in the commonly used Ar/CH4 deposition plasma in a microwave plasma enhanced chemical vapor deposition system. A model for the grain growth is proposed. The films deposited at low TS consist of random/spherical shaped UNCD grains with well-defined grain boundaries. On increasing TS, the adhering efficiency of CH radical onto diamond lattice drops and trans-polyacetylene (t-PA) encapsulating the nanosize diamond clusters break due to hydrogen abstraction activated, rendering the diamond phase less passivated. This leads to the C2 radical further attaching to the diamond lattice, resulting in the modification of grain boundaries and promoting larger sized clustered grains with a complicated defect structure. Introduction of H2 in the plasma at low TS gives rise to elongated clustered grains that is attributed to the presence of atomic hydrogen in the plasma, preferentially etching out the t-PA attached to nanosized diamond clusters. On the basis of this model a technologically important functional property, namely tribology of UNCD films, is studied. A low friction of 0.015 is measured for the film when ultranano grains are formed, which consist of large fractions of grain boundary components of sp(2)/a-C and t-PA phases. The grain boundary component consists of large amounts of hydroxylic and carboxylic functional groups which passivates the covalent carbon dangling bonds, hence low friction coefficient. The improved tribological properties of films can make it a promising candidate for various applications, mainly in micro/nanoelectro mechanical system (M/NEMS), where low friction is required for high efficiency operation of devices.

Growth orientation dependent hardness for epitaxial wurtzite InN films.

We report the hardness of wurtzite InN thin film grown with different crystalline orientations of heteroepitaxial s-plane (1101) and a-plane (1120) on r-plane (1102) Al2O3, and homoepitaxial film on c-plane (0001) Al2O3. Hardness values along with elastic properties are studied using nanoindentation technique. Maximum hardness is reported for c-plane (approximately 8 GPa), which is followed by s-plane (approximately 5.5 GPa) and then a-plane (approximately 4 GPa) oriented InN Films. Peierls force in the slip system of different crystalline orientations for wurtzite sample is calculated for explaining the systematic variations in hardness values of these films grown with different crystalline orientations.