Development of a Cu/MoS2/Ni Self-Lubricating Composite Clad through Laser Additive Approach over a Ti6Al4V Substrate and Its Characterizations.

Solid lubricant coatings play a critical role in enhancing the tribological properties of engineering materials, particularly in aerospace and biomedical applications. Ti6Al4V is widely used in aerospace and defense industries due to its excellent mechanical properties and high strength-to-weight ratio. In this regard, a solid lubricant metal matrix composite (MMC) clad was successfully fabricated over Ti6Al4V. A full factorial (L16) was successfully implemented to investigate the interaction of process parameters for laser power and scanning speed with response outputs, such as the clad layer thickness and microhardness. The microstructural study of the clad confirmed the presence of dark and bright phases of the microstructure with cylindrical, elliptical, and lamellar structures. This showed the presence of molybdenum and sulfide phases (MoS2, TiS, CuS) and the presence of a nickel phase (TiNi, NiS, CuNi), confirmed through X-ray diffraction (XRD) analysis and energy-dispersive X-ray (EDX) spectroscopy; these phases bestowed hardness as well as solid lubricating properties on the clad. The microhardness of the clad was found to be 2-3 times that of the substrate material. The wear behavior of the clad was studied in the load range of 5-15 N; the coefficient of friction (0.33 for clad and 0.5 for base), wear track depth profile, and wear mechanism revealed that the cladded sample has higher wear resistance as compared to the substrate material. The worn morphology showed that microcutting and microplowing are the major phenomena of wear occurrence. Further, X-ray photoelectron spectroscopy (XPS) analysis was performed to determine the binding energy of the compound formed at the clad zone, which can predict the most significant phase for the alteration of the mechanical behavior of the solid lubrication clad.

Effect of Current Waveforms during Directed Energy Deposition of 4043 Aluminum Alloy on Microstructure, Hardness, and Wear of Alloy.

Wire arc additive manufacturing (WAAM) was employed to fabricate 4043 aluminum alloy walls. To investigate the effects of sinusoidal, triangular, and rectangular waveforms of alternating current (AC) and their transients on the wall geometry, microstructure evolution, hardness, and wear properties were evaluated. The root mean square (RMS) current value was maximum for the rectangular and minimum for the triangular waveform. The section produced by the triangular waveform had the highest height-to-width ratio, indicating that this waveform can be a favorable choice for creating components using WAAM. The optical micrographs of the transverse cross-section of the printed sections revealed the grain structure produced with this waveform to be heterogeneous, having a columnar dendritic structure at the bottom and equiaxed at the top portion. The waveforms also had an impact on the hardness and wear characteristics of all the walls, which were attributed to their cooling rate.

Green synthesis of flower shape ZnO-GO nanocomposite through optimized discharge parameter and its efficiency in energy storage device.

Numerous solution-based methods are used to prepare zinc oxide (ZnO) and graphene oxide (GO) nanocomposite (ZnO-GO NCs) such as sol-gel, hydrothermal, and precipitation. These methods require lots of reagents and involve many stages. In this study, a novel one-step solution-based discharge method is used to prepare ZnO-GO NCs through an electrochemical discharge process (ECDP) without the use of any catalyst or toxic chemical reagent. This study focused on analyzing the effects of input parameters on the production rate of ZnO-GO NCs. The experiment was performed by using Taguchi L9 orthogonal array. Materials removal rate (MRR) is considered as output response. The results reveal that voltage is the most significant factor, followed by temperature and duty cycle for obtaining higher MRR. The optimum parameters obtained from the Minitab software for higher MRR are 40 V, 30%, and 45 °C. Further, the morphology of the nanoparticles (NCs) produced at optimum parameters is analyzed which shows flower shape NCs with multilayer graphene oxide, confirmed by the FESEM and TEM images. The XRD peak at 11.27° and Raman spectroscopy peak of G and D bands reveal GO formation. The prepared ZnO-GO NCs tested as supercapacitor activity in the KOH solution. At the optimum parameter, the specific capacitance is observed to be 523.4 F/g at 2A/g current density. The NCs electrode shows good cyclic stability, with 86% retention of specific capacitance after 5000 cycles. This study shows a promising future of converting the e-waste product into valuable nanomaterials such as GO and ZnO from used dry cell batteries.

Fiber Laser Welded Cobalt Super Alloy L605: Optimization of Weldability Characteristics.

The present study describes the laser welding of Co-based superalloy L605 (52Co-20Cr-10Ni-15W) equivalent to Haynes-25 or Stellite-25. The influence of laser welding process input parameters such as laser beam power and welding speed on mechanical and metallurgical properties of weld joints were investigated. Epitaxial grain growth and dendritic structures were visible in the weld zone. The phase analysis results indicate the formation of hard phases like CrFeNi, CoC, FeNi, and CFe in the weld zone. These hard phases are responsible for the increase in microhardness up to 321 HV0.1 in the weld zone, which is very close to the microhardness of the parent material. From the tensile strength tests, the ductile failure of welded specimens was confirmed due to the presence of dimples, inter-granular cleavage, and micro voids in the fracture zone. The maximum tensile residual stress along the weld line is 450 MPa, whereas the maximum compressive residual stress across the weld line is 500 MPa. On successful application of Response Surface methodology (RSM), laser power of 1448.5 W and welding speed of 600 mm/min i.e., line energy or heat input equal to 144 J/mm, were found to be optimum values for getting sound weld joint properties. The EBSD analysis reveals the elongated grain growth in the weld pool and very narrow grain growth in the heat-affected zone.

Electroless Ni-P-MoS2-Al2O3 Composite Coating with Hard and Self-Lubricating Properties.

The work aimed to produce Ni-P-MoS2-Al2O3 on Al-7075 alloys with multiple attributes through an electroless (EL) plating route. The effects of additives (MoS2 and Al2O3) in the EL bath on the surface morphology, topography, hardness, composition (phase and elemental), roughness, wettability, and coating thickness were evaluated. Results indicate a substantial enhancement in microhardness of the EL-coated surfaces by 70% (maximum hardness = ~316 HV) using powders, and 30% (244 HV) without powders. The maximum coating thickness and water contact angle obtained with powders were 6.16 µm and 100.46°, respectively. The coefficient of friction for the samples prepared using powders was 0.12, and for the base material it was 0.18. The compositional analysis through EDS and XRD suggested the incorporation of a hard and lubricious layer on the EL-coated surface owing to the presence of different phases of Al, Mo, P, Zn, O, and S. Therefore, the resulting coating surfaces impart hardness, self-lubrication, hydrophobicity, and wear resistance simultaneously.

Comparison of Maraging Steel Surface Integrity in Hybrid and Conventional Micro-ECDM Processes.

Maraging steel is one of the exotic materials showing the potential for application in the field of the aerospace industry. However, machining these materials with high surface quality and material removal rate is problematic. The micro-electro chemical discharge (MECDM) process is capable of resolving this problem to some extent, however, due to the spark action, it fails to attain a high surface finish. In the current investigation, micro-hole drilling is performed on maraging steel with powder-mixed alumina (1% wt. of Al2O3) using the micro-electro chemical discharge machining (PMECDM) process. The effect of different input process factors, for example, voltage (V), duty cycle (D), the electrolyte concentration (C), are considered for investigating the machining performance, i.e., rate of material removal (MRR) and roughness of surface (SR) of the machined substrate. Further, a comparative analysis is established between micro-ECDM (MECDM) and mixed powder ECDM (PMECDM). The Box-Behnken design is used to conduct all the experiments and analysis of variance (ANOVA) is used to optimize the results. The outcomes reveal that MRR in PMECDM is enhanced by 34%, and the average surface roughness is reduced by 21% over the MECDM process. The maximum MRR was observed to be 2.44 mg/min and the hole machined by the PMECDM results in a cleaner hole wall surface than the MECDM process due to the grinding action by the powder particles. The residual stress measurement indicates that the PMECDM (-128.3 ± 3.85 MPa) has the lowest equivalent stress as compared to the parent material (-341.04 ± 10.24 MPa) and MECDM (-200.7 ± 6.02 MPa) surfaces. The applied voltage is the most significant parameter, followed by the duty factor and electrolyte concentration for enhancing the MRR and surface finish. The addition of powder improves the surface integrity of the machined surface as compared to the surfaces produced by the MECDM processes.

ELEPHANT ENDOTHELIOTROPIC HERPESVIRUS HEMORRHAGIC DISEASE OUTBREAK IN AN INDIAN ZOO.

Elephant endotheliotropic herpesvirus hemorrhagic disease (EEHV HD) is an acute viral infection of growing Asian elephants (Elephas maximus). Four apparently healthy subadult Asian elephants aged between 6 and 10 yr at Nandankanan Zoological Park (NKZP), India, died of EEHV HD during August-September 2019. All four elephants were rescued from different reserved forests of Odisha state at less than 1 yr of age and hand reared in the NKZP. Elephants exhibited the clinical signs of lethargy, head swelling, fever, loss of appetite, abdominal distension, scant urination and defecation, signs of colic, lameness, trunk discharge, cyanosis/ulceration of tongue, erratic behavior, and recumbence before death. Period of illness varied between 28 and 42 h. Thrombocytopenia was the common significant hematological observation. No significant biochemical alterations were recorded except for higher creatinine concentrations. Analysis of blood samples in RT-PCR assay using two different sets of primers and probes that targeted terminase gene and major DNA-binding protein gene followed by cPCR and sequencing was positive for EEHV-1A in all four animals. Postmortem examination of all four carcasses showed hemorrhages in internal organs, including the hard palate, heart, lungs, stomach, mesenteric lymph nodes, mesentery, colon serosa, spleen, liver, kidney, and meninges. Histopathology showed congestion and/or hemorrhages in heart, lung, brain, kidney, and liver. There was presence of intranuclear inclusion bodies in the sinusoidal epithelial cells. The outbreak of EEHV HD that resulted in the acute death of four juvenile captive Asian elephants within <30 d, the first of its kind documented in India, is increasing the fear of similar outbreaks in the future.