Surface Review and Letters最新文献

This study characterizes the microstructure changes of Inconel 718 (IN718) by laser cladding (LC). Well-bonded pore-free, crack-free, single-layer, and multi-layer (overlapped) LC was done on IN718 with the same powder. The basic microstructure illustrates the presence of $\gamma$, $\delta$, and ${\gamma }^{\prime \prime }$ -phases. The precipitation of an irregularly shaped laves phase was observed with dendritic grains in the top and bottom regions of the single-track LC. Further, the epitaxial grain growth of columnar dendrites was observed in the interdendritic region along the laves phase. High leveraging of quick-dissolving behaviors of the laves phase in multi-track LC enhances the high-temperature mechanical performance. Modified grain morphology of the multi-track LC in terms of size, shape, and orientation is reported. Columnar dendrites (short and long) are the most common grains, with varied sizes and orientations reported in line with the Marangoni effect. The microhardness at the top layer of single and multi-track exhibited a higher value of 490.6$$HV and 500.7$$HV, respectively, which is comparatively lower than the bottom layer of single and multi-track samples. The influencing process parameter over clad width is scan speed, and over clad height is powder feed. The nonlinear mathematical model is proposed with a reliability of 99.22% and 99.52% for clad width and height, respectively.

In most of the chemical methods, the as-prepared NPs have a metal hydroxide form. The calcination temperature is very important to prepare the metal oxide from metal hydroxide. Thus, in this work, the chemical precipitation and sol–gel routes were employed to produce the Nickel hydroxide nanoparticles and analyze their functional, structural, thermal, and morphological behavior of prepared NPs. The formation of Ni(OH)₂ is confirmed by FTIR analysis including both techniques. Rietveld refinement techniques were used to diffraction patterns by the program FullProf. The well-matched XRD patterns reveal that prepared NPs have $\beta$-Ni(OH)₂ phase and hexagonal structure (HCP) with a space group of P3m1 for both the methods. The kinetic factors were calculated using different models. The Phadnis–Deshpande model is employed to identify the mechanism of solid state kinetic reaction. Solid state kinetic model observes nucleation and nuclei growth (Avrami–Erofeev nuclei growth) and 2D diffusion mechanism for chemical precipitation and sol–gel, respectively. From the FESEM analysis, flower-shaped architectures and nanosheet morphology are presented in the prepared sample by chemical precipitation and sol–gel, respectively. From the kinetic parameters, we conclude that the decomposition of Ni(OH)₂ to NiO is thermally stable, has slow reaction and spontaneous process at 300^∘C. The results show that the chemical precipitation method is more suitable for energy storage application compare to the Sol–gel method.

This investigation focuses on the study of the effect of process parameters like peak current ($I_p)$, base current ($I_b)$, pulse frequency ($F)$, shielding gas flow rate ($Q)$ on mechanical properties like yield strength (YS), ultimate tensile strength (UTS) and flexural strength (FS) of the welded joints during pulsed TIG welding of SAILMA 450 and EN14 B steels. Taguchi’s L${}_{25}$ orthogonal array has been used for conducting the tests. Multi-objective optimization has been performed using Grey relational analysis (GRA) in order to maximize the mechanical strength and to find out the optimal set of parameters. The optimum parametric combination is obtained at a peak current of 220$$Amps, base current of 120$$Amps, pulse frequency of 5$$Hz and shielding gas flow rate of 17$$l/min. Analysis of variance (ANOVA) is used to predict the significant process parameters. It has been observed from the ANOVA analysis that peak current and pulse frequency have more influence on the output responses than the shielding gas flow rate and base current. The results of the confirmatory test show an improvement of 0.5801 in the GRG, which is satisfactory. A microstructure study has been performed using scanning electron microscopy (SEM) for the optimal set of process parameters.

This paper explains about the mechanical insertion of graphite particles into aluminum (Al-1100) surface for forming composites on the surface through an electrical resistance heat-supported pressing procedure. The surface of the aluminum is first graphite coated by solution casting. To achieve impregnation, the graphite–aluminum interface is locally heated with the assistance of electrical resistance heating followed by mechanical pushing. The degree to which aluminum surface softens can be regulated by process factors like current and heating time. Microstructural characterization of aluminum–graphite composite was carried out with SEM, TEM, Raman spectroscopy and XRD. It was revealed from the microstructural characterization that graphite particles were impregnated into the aluminum surface without agglomeration. Raman spectroscopy of graphite-impregnated surface shows a shift in major graphite peaks and an increased ratio of intensity ($I_D/I_G$). The presence of carbide compound (Al₄C₃) was not detected from the XRD and TEM studies. The mechanical property examination of the surface was carried out by nanoindentation and the subsurface was characterized by microhardness tests. It was observed that surface mechanical property and reduced Young’s modulus were improved by more than 200% and 150%, respectively. The projected method can be utilized as a surface modification technique in solid-state by fabricating surface composites fabricated through mechanical insertion of particulate reinforcement at sub-melting temperatures of substrate and under an open producing environment.

In this study, a novel AA7075-TiO₂ metal matrix composite was machined utilizing a biosilica mixed EDM technique and the surface roughness and material removal rate are optimized. The biosilica particles are produced from waste maize cobs and then silane-treated. The optimization of process variables wasperformed using Taguchi grey relational approach with a process variable of peak current, gap voltage and pulse-on time. Results revealed that the gap voltage is the most important process variable, since it has a larger max-min difference of 0.25. In order to create a high MRR of 11.6$$mm³/min and a surface roughness of 2.25 m, the maximum GRG of 0.79 for Trial 1 (A2B1C3) represents the most ideal process variable group. The best results appear to be obtained with a peak current of 10 A, a gap voltage of 20$$V, and a pulse-on time of 140$$$\mu$s. The new GRG, however, is around 2.51% better than the anticipated optimized process variables of A2B1C3 with an old GRG of 0.79, according to the confirmation research. The new MRR of 11.89$$mm³/min and the surface roughness of 2.30$$s with a GRG of 0.81 are based on the optimized new process variables (A1B1C3).

Public transport via trams has become increasingly important in daily life to meet the growing demand for economic and environmental considerations. In order to ensure the safety of the railway system and reduce service costs, it is necessary to understand the tribological behavior of the system. There are various types of damage such as fatigue, wear, and cracking that can harm the wheels and rails. To determine the wear mechanisms and identify the situations in which wear movements occur, it is crucial to monitor factors such as temperature, surface roughness, and contact micro-hardness between the wheel and the rail. The objective of this study is to analyze the tribological behavior and the impact of climatic conditions on the wheel–rail contact system in the desert area of the Ouargla tramway in Algeria. To achieve this, an intelligent sensor programmed by a microcontroller was utilized to measure the temperature of the wheel–rail contact. Additionally, a hardness tester was used to measure the micro-hardness of the rail, and a roughness tester was utilized to monitor the surface condition of the rail. The measured temperature values during the passage of the tramway varied between ambient temperature and a temperature of 450^∘C. The micro-hardness values ranged from 270 Hv to 440 Hv, and the roughness values varied between 0.4$$$\mu$m and 2.7$$$\mu$m.

Micro-electro-discharge drilling ($\mu$EDD) is a type of non-traditional machining process used for drilling micro-holes of desired dimensions with a high aspect ratio. But, there are no such research works that could have explained the desired accurate circular shape of micro-holes. The need for a more advanced hybrid machining process to improve the overall efficiency in terms of mainly desired circular shape and radial overcut is evolved. In this research work, an electromagnetic field force-assisted micro-EDM process has been carried out on Inconel 800 with a copper tool of 450$$$\mu$m. Experimental results showed that measured metal removal rate and tool wear rate decreased for ascending values of magnetic flux density, peak current and gap voltage, whereas circularity increases linearly with an increase in magnetic flux density and also the effects of magnetic field on circularity of micro-holes on Inconel 800 are more predominant than other parameters.