Surface Review and Letters

Aluminum (Al) and its alloys are attractive for a variety of applications due to its advantages like light weight, ease of processing, and high thermal/electrical conductivities. However, it suffers short comings in terms of strength, wear resistance, and corrosion resistance. Thermal spray processes are widely used techniques for the surface property improvement like thermal, wear, and corrosion resistances of aluminum and other light metals. This paper summarizes the recent developments in thermal spraying and related technologies. Plasma spraying, flame spraying, and arc spraying are the chief thermal spraying techniques, whereas the HVOF and D-gun processes are the derivatives of flame spraying process. The cold spraying technique is an emerging coating technique where the particles are heated to a temperature lower than their melting point travel at high velocity and coat on impact with the target material by plastic deformation. Different parameters like heat source characteristics, coating material properties, substrate properties, and spray torch operating circumstances affect the coating microstructure and properties.

Moulds are used in industries to make plastic parts that require clear and defect-free surfaces. So, mould cavity surfaces must be finely finished. The novel magnetorheological grinding (MRG) process is employed in this study to fine finish the H13 circular tapered mould cavity surfaces, which are generally used for producing light covers. To achieve finely finished circular tapered mould cavity surfaces, the best process employing parametric combination of current, rotating workpiece, rotational and reciprocation speeds of MRG tool is obtained using the Taguchi technique. The roughness value on the circular tapered lateral and closed-end surfaces of the mould cavity decreased to 70nm from 450nm and to 60nm from 320nm, respectively, after using the present method with the best parametric combination. The surface characteristics improved significantly. Thus, the present process can help to achieve finely finished H13 circular tapered mould cavity surfaces for making clear and defect-free polycarbonate light covers.

Unsteady thin hybrid nanoliquid film flow over a stretchable cylindrical surface is studied with the uniform thickness of hybrid nanoliquid. The combined effects of different nanoparticles like single-walled carbon nanotubes (SWCNTs), multi-walled carbon nanotubes (MWCNTs) and copper (Cu) are considered for investigation in the presence of thermocapillarity, magnetic field and thermal radiation. The finite difference technique is applied to solve the governing set of nonlinear equations. Result showed that the hybrid nanoliquid film thinning rate declined with the higher volume fraction of different nanoparticles. The hybrid nanoliquid film thickness enhanced with higher values of radiation parameter and magnetic field. A curve $Z=Z_c$ is described within the hybrid nanoliquid film which separated total flow region in two zones. In one side of this curve, heat is transferred from the cylindrical surface to the hybrid nanoliquid film and in the other side, opposite scenario is observed.

The main objective of this work is to study the effects of surface texture direction on contact and wear characteristics of point grinding parts under dry sliding contact. This study provided a method to obtain the surface with good contact characteristics and wear resistance under certain working conditions. The point grinding surface texture model, the contour support length model considering surface texture, and the fractal contact model of the cylindrical surface were built. The measuring experiment was carried out using TR300 roughness shape measuring instrument and the tribological experiment was carried out using HSR-2M high-speed reciprocating friction and wear tester. The results showed that the surface texture direction had an effect on the contour support length ratio, the contact and wear characteristics of parts. When the surface texture direction angle was 30^∘, the average friction coefficient was the smallest, the supporting performance and wear resistance of parts were the best; for surfaces with 30^∘ and 60^∘ texture, the fluctuation of the friction coefficients was smaller, the wear uniformity was better; when the load was small, the abrasion loss of point grinding parts will decrease with increase in the direction angle of surface texture. The results can help to choose appropriate processing method and machining parameters to obtain appropriate surface.

The biodegradable magnesium (Mg) alloys have been acknowledged amongst the top potential biomedical materials for developing different orthopedic devices. Indeed, the processed Mg alloys’ surface integrity shows a substantial contribution to the resulting biomedical applications’ performance. In this paper, the effect of various influential process parameters of an ultra-precision diamond turning (UPDT), such as rotational frequency of spindle, tool overhanging (TOH), feed rate (FR), and depth-of-cut (DOC) on the chip formation, shearing mechanism, and surface finish of the biodegradable Mg AZ31 alloy have been studied. The resulting chips’ analysis of the different processing parameters has been studied to investigate the involved shearing mechanism. Besides, a relationship between the resulting surface topography and the consequences of UPDT-parameters on skewness (${{𝒮}}_{\mathrm{\text{sk}}}$) and kurtosis (${{𝒮}}_{\mathrm{\text{ku}}}$) was studied. The statistical analysis highlighted that the FR and TOH significantly influenced the surface roughness of the Mg AZ31 alloys at a 95% confidence level. Therefore, being statistically dominating, the morphology of the formed chip has also been influenced by FR and TOH’s parametric levels. The UPDT-processed Mg-alloy possessed a nano-finished surface that acted as hydrophobic and could prevent the surface from corrosion. In the light of experimental findings, the UPDT-processed Mg-alloy can be used for orthopedic screws and plates applications.

The braking system is the most significant active safety system that converts the vehicle’s mechanical energy into heat energy based on the braking pair’s friction. In this paper, temperature-friction coefficient variation, disc thickness variation, and coning are investigated with the Fade I test procedure is performed according to the SAE J2522 comprehensive brake efficiency test standard. In these investigations, the combined or discrete effects of the peripheral speed factor, the temperature increase with the braking time, thermal expansion and increased friction coefficient values have been decisive on the increase in the disc thickness variation from the inner part to the outer part. The thermo-mechanical behavior of the disc for the same test procedure is demonstrated in ANSYS^® software using the finite element method. Steady-state thermal analysis method is chosen, and then total deformation and von Mises stress conditions are evaluated by using transient structural analysis with thermal analysis results and experimental data. At the end of braking, the deformation has reached its 0.28872 mm (maximum) at the outer radius where the pad and disc are in contact, and the maximum von Mises stress value (964.33 MPa) has been obtained. Furthermore, the deformations reached the maximum in the region where the disc temperature reached its maximum during braking revealing that the obtained results are interrelated.

Internal turning process is generally used to finish on the internal part of the cylindrical workpiece. This may create degraded surface and high tool wear without and with the usage of coolants. This novel work investigates the internal turning of aluminum alloy using three cutting environments, i.e. dry, flood, and minimum quantity lubrication. The effect of variable machining parameters and cooling media drives the surface quality and tool effectiveness. The in-house fabricated experimental setup was used for the experimental work. A specially designed mist nozzle produces an aerosol used for sustainable machining. Shiny chips and improved surface finish are achieved during near-dry machining, even at higher feeds. The presented method’s usefulness is attributed to high levels of association among conceptual, empirical, and literature survey results. The mist produced by supplying aerosol internally through a boring bar proved an effective technique for better surface integrity than conventional and flood lubrication. Machining productivity increases significantly with an improved surface characteristic and less tool wear.

The carbon nanotubes grafted methylene blue molecularly imprinted polymers (CNT-MB-MIPs) were prepared by grafting aminated carbon nanotubes (CNTs) and copolymerized in the presence of template molecules methylene blue (MB), functional monomers, crosslinkers, and initiators. The results from structural analyses indicate that CNTs were successfully grafted onto the molecularly imprinted polymers (MIPs). The adsorption experiments showed that the adsorption capacity can be affected by grafting CNTs. The adsorption capacity of CNT-MB-MIPs on MB can reach 2793mgg${}^{-1}$ while the initial concentration of MB was 12gL${}^{-1}$, which was higher than that of MB molecularly imprinted polymers (MB-MIPs). Meanwhile, compared with MB-MIPs, CNT-MB-MIPs had a lower adsorption capacity for iron ions, indicating that CNT-MB-MIPs could inhibit the adsorption of iron ions. Adsorption kinetics study showed that the adsorption mechanism of the polymer for MB was in good agreement with the quasi-second-order kinetics model ($R^2=0.9978$) and the adsorption mechanism for iron ions was also in good agreement with the Bangham kinetics model ($R^2=0.9475$). The adsorption isotherm showed that the adsorption process of the two adsorbents was mainly monolayer chemisorption. The remarkable adsorption capacity of CNT-MB-MIPs may be due to the enlargement of adsorption sites on MIPs surface by CNT-NH₂ grafting. At the same time, it can inhibit the adsorption of iron ions, because part of the carboxyl groups in CNT-MB-MIPs are bonded by CNTs, led to few carboxyl groups sites left for adsorbing iron ions, thereby the complex between carboxyl groups and iron ions were inhibited.

Aluminum and its alloy are versatile metal materials engaged in various applications based on their high strength, corrosion resistance and light weight. However, there are many limitations to its applications when compared with steel. In a bid to improve on the properties, aluminum composites are developed. In this study, Al 6111 composite was developed by the blend of silica and bamboo leaf ash (BLA) as reinforcement employing stir casting process. The input factors for the experiment were silica dosage (A), BLA proportion (B) and stirring temperature (C). The experimental design was carried out via Box Behnken design of the response surface methodology. Composites were fabricated through stir casting process by varying the inputs according to the dictations of the experimental runs. Parameters evaluated are yield strength, ultimate tensile strength, elastic modulus and elongation. Result of the ANOVA analysis showed that the parameters had consequential effect on the response and the developed model for each parameter are fit for predictions. From the surface plot, interaction between 5wt.% and 10wt.% silica and 2wt.% and 4wt.% BLA led to improvement in yield, ultimate tensile strength but decrease in elongation even as proportions 10wt.% and 15wt.% silica and 4wt.% and 6wt.% BLA ensued reduction in the value. Stirring temperature of 700–800^∘C is favorable to the strength parameters while 800–900^∘C led to strength reduction. Optimization via response surface, predicted optimum conditions of 11.6249wt.%, 3.95707wt.% and 789.033^∘C for A, B and C, respectively. Predicted values for yield strength, ultimate tensile strength, elastic modulus and elongation are 278.26MPa, 378.24MPa, 97.7885GPa and 10.132%, respectively. Validation experiment was carried out at the optimum condition and the deviation in parameters between the predicted and validated values is $<5\%$. Hence, the models are statistically fit for property predictions.

The AA7075 composites reinforced with 3, 6, and 9 volume fractions (vol.%) of ZrB₂ particles have been successfully fabricated using in situ fabrication method. In this technique, the inorganic salts K₂ZrF₆ and KBF₄ were added to the molten aluminum and retained the melting at 900^∘C to form the required vol.% of ZrB₂ particles. The aluminum-reinforced metal matrix composites (MMCs) are commonly known as aluminum matrix composites (AMCs). This work carries the effects of various wire electrical discharge machining (WEDM) input process parameters like pulse-on-time ($T_{\mathrm{\text{on}}}$), pulse-off-time ($T_{\mathrm{\text{off}}}$), wire feed rate (WFR), and gap voltage (GV) on the output responses such as material removal rate (MRR), surface roughness (SR), and Kerf-width ($K_W$) of the fabricated AA7075/(3, 6, and 9) vol.% ZrB₂ in situ AMCs. Based on Taguchi’s L9 orthogonal array method, the design of experiments (DoE) was used to carry out the operations on the fabricated AMCs. The optimal level of process parameters was found by the main effects plot for signal-to-noise (S/N) ratio, contour plots, and the analysis of variance (ANOVA). The effect of these process parameters on MRR and SR was analyzed and it is found that the maximum MRR was attained in the optimal parametric combination of GV $=60$V; $T_{\mathrm{\text{on}}}=4$$\mu$s; $T_{\mathrm{\text{off}}}=6$$\mu$s; WFR $=12$mm/s; Reinforcement $=3$ vol.%, and the minimum SR was attained in the optimal parametric combination of GV $=60$V; $T_{\mathrm{\text{on}}}=2$$\mu$s; $T_{\mathrm{\text{off}}}=9$$\mu$s; WFR $=8$mm/s; Reinforcement $=3$ vol.%.

In this study, cementation steel was boronized at 1050^∘C for 6h, 8h, and 10h. Microstructural change on the surface of the samples after boronization was detected by optical microscope (OM), scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), X-Ray diffraction (XRD), and electron back scatter diffraction (EBSD) analyses. Also, surface roughness, microhardness, and layer thickness were measured. FeB, Fe₂B phases, and saw tooth morphology expected in iron-based metals during boring process occurred in the entire process time. The average layer thickness of the boronized samples at 1050^∘C for 10h was measured as 222$\mu$m and the surface roughness value was 3.40$\mu$m. The hardness of boride phases acquired on the samples varied between 1700 HV and 1730 HV. As a result, while the ratio of chromium carbide is the highest in the base metal, the boron level was the highest in the coating. Compounds 49wt.% Cr₇C₃ and 47wt.% B were identified as the most intensely concentrated.

In this work, we prepared LaNiO₃ (LNO) and Au-LaNiO₃ (Au-LNO) films using sol–gel multilayer coating method. The effects of lattice mismatch on the microstructure and electrical properties of the films were investigated by choosing different single-crystal substrate. XRD, SEM, and AFM results showed the high quality of LNO and Au-LNO films, indicating the successful epitaxial growth of the films on the single-crystal substrates. The room temperature resistivity of LNO films increased with the increase of lattice mismatch while different tendency was observed in Au-LNO films, suggesting that different mechanisms prevailed in the LNO and Au-LNO films. Both the transport behavior and the residual resistivity ratio were checked to explore the relationship between the lattice mismatch and the electrical properties of the films. Strain and defect concentration were proposed as the predominating factors for the changes in the resistivity of LNO and Au-LNO films under the influence of lattice mismatch.

The aim of this paper is to study the stress distribution law of corrosion defects in pipelines before and after repair of thin-walled lining and the effect of repair. The calculation model for corrosion defects in pipelines was established by the equilibrium differential equation of elastic–plastic mechanics. Based on ABAQUS finite element software, the pipeline model with a single corrosion defect was established. The material of the pipeline was API 5L X52N with an outer diameter of 324mm and a thickness of 10mm. The material constitutive relation was an ideal elastic–plastic model. We changed the depth-to-thickness ratio of corrosion defects ($d∕h=0$, 0.1, 0.5, 0.8) and used the different lining repair materials (stainless steel and FRP). At the same time, ignoring the thickness of bonding layer and its influence on the filling of corrosion pit, the interface interaction analysis model was established by the bonding behavior between layers. We compared the stress at the corrosion defect before and after repair. It is found that with the increase of the depth-to-thickness ratio of corrosion defects, the radial stress, circumferential stress, and Mises stress at the corrosion defect all tend to increase. The circumferential stress at the defect before the repair is the largest, and its value is similar to the Mises stress. After the repair of stainless steel lining, the circumferential stress at the defect is reduced by 11.01%, and the Mises stress is reduced by 14.18%; after the repair of FRP lining, the circumferential stress at the defect is reduced by 7.01%, and the Mises stress is reduced by 3.54%. The depth-to-thickness ratio of corrosion defects has a significant impact on the stress distribution of pipelines. Therefore, the influence of corrosion depth should be paid attention to in the pipeline safety assessment. Before and after repair, the control stress at the corrosion defect of the pipeline is always the circumferential stress. The failure can be judged according to the circumferential stress; after the repair of thin-walled lining, the stress at the original defect is redistributed, and the circumferential stress and Mises stress are reduced, and the repair effect is obvious.

The wear reduction of moving components is highly desirable because wear limits their reliability and service life, mainly at elevated temperatures. This study produced thick clads of NiCrSiB/WC/MoS₂/BaF₂ by tungsten inert gas (TIG) and microwave hybrid heating (MHH) cladding techniques, which were compared for microstructural and high-temperature tribological properties. The clad samples were subjected to sliding contact using a pin on disc tribometer at 200^∘C, 400^∘C, 600^∘C under 20 and 40N load. The worn surface was analyzed using FESEM, XRD and three-dimensional (3D) profilometer. The experimental results revealed a significant effect of the TIG current and MHH exposure time on the microhardness value, which predominantly depends on the morphological characteristics. The average hardness of TIG clads was found to be 1.2 times higher than the MHH clad. Because of the MoS₂ and BaF₂ encapsulation, the continuous lubricant layer formation compensated for improved wear resistance with good reliability and longer service life. This work provides significant insights into the wear behavior of TIG and MHH clads at elevated temperatures and the prospective applications in turbines, where inadequate wear resistance of titanium alloy is the major concern for its use.

Carrying out an engineering process with the least cost and within the shortest time is the basic purpose in many fields of industry. In Computer Numerical Control (CNC) machining, performing a process by following a certain order reduces cost and time of the process. In the literature, there are research works involving varying methods that aim to minimize the length of the CNC machine tool path. In this study, the trajectory that the CNC machine tool follows while drilling holes on a plate was discussed within the Travelling Salesman Problem (TSP). Genetic Algorithms (GA), Particle Swarm Optimization (PSO), and Grey Wolf Optimizer (GWO) methods were used to solve TSP. The case that the shortest tool path was obtained was determined by changing population size parameter in GA, PSO, and GWO methods. The results were presented in tables.