Surface Review and Letters

Ni-based superalloys fall under the category of difficulty in machining type material owing to their poor thermal conductivity and high strength at extreme temperatures. Machining such materials using the traditional approach is a tremendously difficult task. On the other hand, EDM, one of the most sophisticated electro-thermal manufacturing processes, is used to machine such materials. It is a well-known non-traditional machining process for generating parts that require accuracy, have complex shapes, and are small in size. However, the use of EDM in Ni-based superalloys has some disadvantages like poor surface finish and low material removal rate. So, to alleviate these disadvantages, researchers introduced powder mixed dielectric fluid in the EDM process. Further, the performance of this technique has been enhanced by studying the effect of various nano/micro-size particles and their concentrations in the dielectric medium. In this paper, the authors have reviewed the impact of non-electrical and electrical process parameters on the output responses when machining Ni-based superalloys using powder mixed EDM. The challenges faced during the conventional machining of Ni-based superalloys and the mechanism proposed for powder mixed EDM, especially under the influence of suspended powders into the dielectric medium have also been presented in this paper. Finally, future research areas of powder mixed EDM of Ni-based Superalloys, such as (i) its modelling and simulation and (ii) the effect of tool motion and powder properties on its performance, are discussed in brief.

In manufacturing industries, polymers are widely used due to their exceptional physiochemical and mechanical characteristics. It consists of high strength, low weight, corrosive resistivity, and ease of fabrication. Glass fiber is more cost-effective and easily available than other fibers such as carbon, aramid and kevlar. The most challenging issue for the manufacturer in the laminated polymer is the non-homogeneity and anisotropic behavior. This nature also hinders the machining performance of laminated polymer composites, which are entirely different from metals and their alloys. The supplements of nanomaterials enhanced the physiomechanical properties and the machining efficiency of fiber laminates. This work highlights the machining (drilling) aspect of glass fiber-reinforced polymer composites modified by multiwall carbon nanotube (MWCNT). The effect of drilling factors such as spindle speed ($S$), feed rate ($F$), and MWCNT weight percent (wt.%) on machining responses such as Thrust force (Th), Torque ($T$), and Surface roughness (SR) has been investigated. The drilling operations were conducted using the 5 mm diameter TiAN (Sic coated) according to the response surface methodology (RSM) design. The process constraints were controlled by the hybrid module of additive ratio assessment (ARAS) and the Artificial Bee Colony (ABC) algorithm. The nature-inspired principles of the bee are used to optimize the objective function. The multiple responses were aggregated using the ARAS method, and its objective function is fed into the ABC algorithm. It was remarked that the hybrid ARAS-ABC is more capable than the traditional ARAS, with an overall improvement of 7.33% in assessment values. The scanning electron microscopy (SEM) test confirms the feasibility of the proposed hybrid (ARAS-ABC) module to achieve a favorable machining environment while drilling modified nanocomposites.

The degradation control of implants has now become a most critical factor for investigation. The rapid degradation or uncontrolled degradation of metals causes allergic reaction and implants failure. The biocompatibility and biodegradability of biometals are essential properties for the development of bioimplants. The biodegradation is the chemical reaction of implants metal with the surrounding body fluids. The gradual dilution of metal oxide with the body fluid is considered as a degradation. Magnesium, zinc, and iron metals are biodegradable metals. The biodegradability of as-cast metals is not capable of fulfilling the need of patients, therefore, degradation of implants is required to be in control. Many more research articles have been published on improvement of corrosion resistive implant surface by coating, passivation oxide layer, plasma spraying, electropolishing, blasting, chemical etching, laser treatment, heat treatment, severe plastic deformation (SPD), alloying, and development of surface composites. This paper critically reviewed the surface modification and surface composite fabrication techniques to improve the biodegradability, biocompatibility, and strength of implants.

The use of carbon fiber-reinforced polymer (CFRP) composites having low weight and high strength provides the substantial energy savings in space and aerospace industry. The disadvantage of these composites is that the carbon fiber is not firmly bonded to the epoxy resin and the toughness of the produced materials is low. Graphene (G) and Graphene Oxide (GO) nanoparticles are used to functionalize CFRP composites. The CFRP composites functionalized with G and GO improve the strength of these composites by improving the fiber/matrix interface bond. In this study, the effect of type of nanoparticles, feed rate, cutting speed and number of flutes on machinability (cutting force, delamination factor and surface roughness) were experimentally investigated in the milling of CFRP composites, G-CFRP (CFRP functionalized with G) and GO-CFRP (CFRP functionalized with GO) nanocomposites. Cutting force, delamination factor, and surface roughness were found to be strongly impacted by feed rate, cutting speed, number of flutes, and type of nanoparticles. The increase in the number of flutes contributed to decrease of cutting force, delamination factor and surface roughness, while the increase in the feed rate caused to increase of them. By increasing cutting speed, surface roughness reduced, delamination factor and cutting force increased. In addition, compared to the CFRP composite, the cutting forces and surface roughness were higher, and delamination factor was lower in the CFRP composites functionalized with G and GO.

In this study, Inconel 625 (IN625) alloy and tungsten carbide (WC) with additive ratios of 10%, 30% and 50% by weight were coated on the magnesium alloy surface. The coating process was carried out with the High Speed Oxy-Fuel Spray (HVOF) technique. Microstructure characterizations were performed by profilometry, optical microscope (OM), scanning electron microscope (SEM), energy distribution X-ray spectroscopy (EDS) and X-ray diffraction (XRD) analysis. Microhardness measurements and wear tests were also used to determine mechanical properties. Dry sliding wear tests were carried out at loads of 2, 6 and 10 N and at a sliding distance of 150 m. It has been observed that powder mixtures with different additive ratios form different microstructures. It was observed that the Surface Centric Cubic Structure (FCC) $\gamma$ (gamma) matrix and WC carbide as well as W₂C, W₆C${}_{2.54}$, M₆C and M${}_{23}$C₆ carbides were formed on the obtained coating layers. Depending on the increase in WC additive ratio, the surface roughness values increased. The microhardness values in the coating layers varied between 392 and 508 HV${}_{0.1}$WC additive to Inconel 625 improved its hardness and wear resistance. While 0.64, 0.97 and 1.19 mg weight loss was measured for 2, 6 and 10 N in the pure AZ91 sample, these values were 0.12, 0.2 and 0.31 mg in the IN625WC-50 sample measured. The coating with the highest hardness and wear resistance was obtained with a high WC ratio.

This paper describes the pulsed Nd:YAG laser machining characteristics on 6351 aluminum reinforced with silicon carbide (SiC) and boron carbide (B₄C) particles. The composites are prepared using stir casting route by varying the weight percentage of B₄C (0, 5, and 10 wt.%). During experimentation, the traverse speed (5, 15, and 30 mm/s) and the laser pulse frequency (5, 9, and 15 kHz) are considered to evaluate the groove width. The results reveal that the lower pulse frequency produced poor groove surface quality. Higher thermal energy dissipation at lower traverse speed may also result in the formation of recast layer and heat-affected zone. This is evident from the microscopic image and the EDS analysis. Thus, the optimum condition (composite with 10 wt.% B₄C machined at 30 mm/s and 15 kHz) to achieve minimum grove width with improved surface morphology is identified by desirability analysis. Additionally, the regression model is developed to predict future values ($R$² at 91.86% and $R$² (adj) at 87.55%). Finally, the probability plot confirms the effectiveness of the proposed model at 95% confidence level.

In the plasma etching technique, acquiring a high-quality transfer from the mask pattern onto the substrate under the suppression of the charging effects is of great significance. Most previous publications only focus on studying the charging phenomena on smooth round mask holes. This work shifted the target to an isolated mask hole with a rough edge using a classical particle simulation program, to examine the effects of edge roughness on surface charging for a mask hole. This study adopted the CF₄ plasmas, due to the widely used fluorocarbon plasmas for the contact-holes. Simulated results indicate that the mask holes with various shapes present differences in electric field ($E$-field) strength distribution, etching rate and profile evolution, relying on some condition parameters (roughness and reflection probability on the mask surface). The larger the dominant wavelength (DW), the more uniform the $E$-field distribution around the edge of the mask hole will be. The simulation of the profile evolution further confirmed that the deformation is in keeping with the distribution of the $E$-field. It was further found that the root mean square (RMS) of roughness increases with time in cases of the relatively small values of wavelength (10 and 35 nm) and decreases for other cases. Possible mechanisms behind have been discussed in detail. The findings of this work would shed light on an approach to maintain the pattern integrity.

The pinion and crown are key components in an automobile’s transmission system. The surface characteristics of high-carbon steel have a major effect on differential gear action. As a result, gear damages and increased downtime for repairs are experienced over time. To address this issue, manufacturers have started using alternative materials such as aluminium alloys and composites to improve the durability and efficiency of the transmission system. Engineers can now adjust the design of crown and pinion gears for best performance thanks to developments in computer-aided design and simulation tools. This has led to the development of more compact and lightweight transmission systems that offer better fuel efficiency and acceleration. However, these innovations come at a cost, as they require specialized manufacturing processes and materials that can be expensive. Nevertheless, the benefits of improved transmission systems are clear, as they can significantly enhance the driving experience while reducing maintenance costs over time. As technology continues to evolve, we can expect further improvements in material design that will further enhance crown pinion performance and reliability. To overcome these failures and increase the material’s life, high-carbon steel is preferred. In this study, high-carbon steel composites with various material proportions (100% to 0%, 99% to 1%, and 97.5% to 2.5% of high-carbon steel, and silicon carbide, respectively) are experimentally investigated and evaluated for better structural strength and surface behavior of the crown pinion. The crown pinion is thoroughly analyzed using salt spray corrosion testing and X-ray diffraction analysis. According to the results, the proportion of 97.5% high carbon steel with 2.5% silicon carbide has better surface properties than the other proportions, and it is also recommended to make the crown pinion for future uses.

The product’s surface quality and service performance depend on the surface integrity features formed by the machining process. Surface integrity consists of many features including surface topography and others. In this work, 3D (areal) surface topography features, particularly height variations, were investigated on the polycrystalline diamond (PCD) turning of alumina. Variations of the areal unevenness and height distribution parameters, namely arithmetic mean deviation (Sa), maximum peak height (Sz), skewness (Ssk) and kurtosis (Sku), with respect to turning parameters such as spindle speed (1000, 2000 & 3000 rpm), feed rate (0.05, 0.075 & 0.1 mm/rev) and depth of cut (1, 3 & 5 $\mu$m) were studied. The Taguchi technique was carried out in this study based on the L₉ standard orthogonal array for optimizing the turning parameters for the generation of better topography features. The error analysis was done with the experimental results and the error variations were noticed to be less than 10%. Based on the experimental results, the best surface figure combination of Sa 0.67 $\mu$m, Sz 3.18 $\mu$m, Ssk 0.0039 and Sku 3.06 was found at the employment of spindle speed of 1500 rpm, feed rate of 0.1 mm/rev, and depth of cut of 1 $\mu$m. The distribution of peaks and valleys formed over the PCD-turned alumina surfaces may influence the different functional properties such as fatigue, friction, wear, etc. Besides, the results were examined through means of responses and analysis of variance (ANOVA). The test results also reported that the depth of cut outperforms other hard turning parameters over the surface topography features of the turned alumina ceramics. At a lower depth of cut, the cutting tool is involved in the shearing action which causes the stable material removal of alumina ceramics through an appreciable chip formation.

In this study, analyses were carried out to investigate the structural, mechanical and electrochemical behaviors of untreated and bioglass (BG)-coated Ti45Nb materials. The samples were coated with a mixture of 63s BG powder and phosphate ester (PE) at concentrations of 0.2, 0.4, 0.8, and 1 g using the electrophoretic deposition (EPD) method. Then, the structural, mechanical, and electrochemical properties of the untreated and coated samples were determined and characterized by using X-ray diffraction (XRD) and scanning electron microscope (SEM) devices. It was concluded that the 0.2 g coating provided resistance to corrosion for the Ti45Nb material more effectively than the others did.