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The machinability of aluminum alloy (Al-6082) has the scope of enhancement by integrating Friction Stir Processing (FSP) with tool geometry, tool shape and different tool materials. In this research, the role of tool pin shape has been studied by experimenting on various tool shapes (square, hexagonal and octagonal) with the aim of machinability improvement. In FSP, the tool rotation speed is 930rpm and tool travel speed is 26mm/min. The specimens have undergone tensile, microhardness and microstructure testing using optical microscope and scanning electron microscopy. The percentage elongation has been increased from 15% to 29% in the case of the octagonal-shaped tool pin; similarly, the (Vickers’) microhardness value is 14.6% higher than the square- and hexagonal-shaped tool pins. Among these tool pin shapes, the octagonal-shaped tool pin succeeded in providing the best-in-class machinability performance on Al-6082 T6 alloy with FSP. It may unveil the newer scopes of FSP on Al-6082 for automotive components assembly and other similar applications.

This study examined the microstructural, mechanical, and corrosion behaviors of a multidirectional-forged (MDF) Mg–Zn–Ca alloy. The results showed significant grain refinement of the alloy after 5 passes of the MDF process from 378$\mu$m to 23$\mu$m. X-ray diffraction analysis (XRD) revealed the presence of finer Mg₇Zn₃ phases and $\alpha$-Mg and Ca₅Zn₃ phases after the MDF process and peak shift and broadening. Higher hardness ($76.46\pm 3$) was noticed in the MDF 3 pass sample due to grain refinement; further hardness slightly decreased due to texture softening. Moreover, the results of the in vitro corrosion experiments conducted in SBF solution showed that the corrosion current densities of the alloys move in a noble direction as the number of MDF passes increases. MDF 3 pass sample (0.00523mm/y) showed the lowest degradation rates compared to the as-cast sample (0.01154mm/y), attributed to refining and redistributing the second phases.

Laser-based surface enhancement techniques improve metals’ mechanical properties. Laser Hardening (LH) and Laser Shock Peening (LSP) techniques are effective particularly well with low-alloy steel made of 34Ni-Cr-Mo6, which is a type of steel alloy that is put to use in a wide variety of fields because it possesses excellent levels of both strength and toughness. For specific applications, the laser can be shaped into line or spherical beams. On the other hand, typical industrial requirements of low alloy steel components like 34Ni-Cr-Mo6 are enhanced hardness and mechanical strength with minimum or no distortion. A 3 kW high power fiber laser with a flat top-hat beam of dimension $30\times 1$mm and a circular beam of Ø6mm are employed in this study. Investigation into the effects of repeated LSP on the microstructures and residual stress of 34Ni-Cr-Mo6 low alloy steel was also done. LSP treatment is carried out at 6.36GWcm${}^{-2}$ Laser Power Density (LPD) with different laser impacts, i.e. single and double, by keeping 0% overlap along the scanning direction and perpendicular directions, respectively. The shock-peened samples were characterized in terms of residual stress measurements and microstructural evolution using different characterization techniques. A substantial improvement in compressive residual stress was observed at the hardened cross-section i.e. $\sim -260$MPa and at shock peened surface $\sim -620$MPa respectively as compared to the as-received sample ($\sim -100$MPa). LH samples showed a better result in terms of microhardness values when compared to shock peened samples i.e. for LH, the microhardness values at the cross-section were $\sim 710\pm 40$HV${}_{0.5}$ nearly 2.5 times increase in hardness. Extreme plastic deformation was found by microstructural examination of cross-sections of LSP-treated areas. Hardness was nearly marginally improved in multiple times LSP-treated samples compared to unpeened ones as a result of LSP.

In this study, the tribological behavior of Tungsten Inert Gas (TIG) welded Inconel 617 alloy has been studied using the Pin-on-disc tribometer. TIG welding was performed after imparting surface coatings to the Inconel 617 alloy which was coated with a blend of Silicon dioxide (SiO₂) and Titanium dioxide (TiO₂) in different proportions. Three samples were prepared by varying the coating composition and weld current. The Coefficient of Friction (COF), wear depth ($\mu$m) and hardness of the samples were estimated. Microstructure analysis and X-ray diffraction (XRD) analysis were also carried out on the samples. The wear depth of the Inconel 617 substrate, as well as weld bead samples 1, 2, and 3, were 2055.1, 415.39, 463.17, and 560.68 $\mu$m respectively. The COF for the Inconel 617 substrate and weld bead samples 1, 2, and 3 were determined as 0.384, 0.491, 0.471, and 0.455 respectively. By analyzing the results of the wear test, it was observed that ‘sample 1’ welded at the lowest heat input of 4.32 kJ/mm, exhibited superior tribological characteristics including reduced wear (415.39 $\mu$m) and an increased COF (0.491) compared to the other samples. The enhanced tribological performance could be attributed to factors such as the presence of carbides like TiC and notably the higher hardness (284.12HV) exhibited by ‘sample 1’.

In the present study, TiN coatings have been deposited on D2 tool steel substrates by using cathodic arc physical vapor deposition technique. The objective of this research work is to determine the usefulness of TiN coatings in order to improve the micro-Vickers hardness and friction coefficient of TiN coating deposited on D2 tool steel, which is widely used in tooling applications. A Pin-on-Disc test was carried out to study the coefficient of friction versus sliding distance of TiN coating deposited at various substrate biases. The standard deviation parameter during tribo-test result showed that the coating deposited at substrate bias of -75 V was the most stable coating. A significant increase in micro-Vickers hardness was recorded, when substrate bias was reduced from -150 V to zero. Scratch tester was used to compare the critical loads for coatings deposited at different bias voltages and the adhesion achievable was demonstrated with relevance to the various modes, scratch macroscopic analysis, critical load, acoustic emission and penetration depth. A considerable improvement in TiN coatings was observed as a function of various substrate bias voltages.

Cathodic Arc Physical Vapor Deposition (CAPVD), a technique used for the deposition of hard coatings, for tooling applications, has many advantages. The main drawback of this technique is the formation of macrodroplets (MDs) during deposition, resulting in films with rougher morphology. Constant etching, by increasing nitrogen gas flow rate up to 200 sccm, helped in reducing the MD size and number; at higher rates, of say 300 sccm, the behavior was reversed. Minimum value of surface roughness recorded at 200 sccm was measured via both surface roughness tester and atomic force microscopy (AFM). Micro-Vickers hardness of TiN-coated tool showed about 564% times increase in hardness than the uncoated one. Scratch tester was used to study the critical loads for the coating and the excellent adhesion achievable, of say 200 sccm, was demonstrated, with relevance to the various modes.

Titanium Carbonitride (TiCN), a new high hardness and wear-resistant material, has been applied widely in many fields. TiCN coating was first fabricated using reactive plasma spraying (RPS) technology in the reactive chamber that was filled with nitrogen and acetylene (N₂ and C₂H₂) in this study. The microstructure and the phase composition of the coatings were analyzed by SEM and XRD. More chemical information of surface was analyzed by XPS. The Vickers microhardness of TiCN coating is 1659.11 HV_100g, and the cross-section of the coating shows a conspicuous phenomenon of indentation size effect.

Mg alloys are ultralight but their structural applications are often limited by their poor wear and corrosion resistance. The research aimed to address the problem by laser-cladding. Cladding with SiC powder onto surface of AZ91D was carried out using Nd:YAG laser. The laser-clad surface was analyzed using the optical microscope, SEM equipped with EDS, and XRD and found to contain SiC and other Si compounds such as Mg₂Si and Al_3.21Si_0.47 as well as much refined α-Mg grains and β-Mg₁₇Al₁₂ intermetallics. The laser-clad surface possesses considerably higher hardness but its corrosion resistance is not improved, indicating that the laser-cladding technique can only be adopted for applications in noncorrosive environments where wear is the predominant problem.

Al₂O₃ coatings were prepared on T6-tempered Al6061 alloys substrate under a hybrid voltage (AC 200 V–60 Hz and DC 260 V value) by plasma electrolytic oxidation (PEO) in 30 min. The effects of different electrolytes on the abrasive behaviors of the coatings were studied by conducting dry ball-on-disk wear tests. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to investigate the coating microstructure. XRD analysis results show that the coatings mainly consist of α- and γ-Al₂O₃, and some mullite and AlPO₄ phase in Na₂SiO₃ and Na₃PO₄ containing electrolytes, respectively. The wear test results show that the coatings which were PEO-treated in Na₃PO₄ containing electrolyte presented the most excellent abrasive resistance property.

Reactive plasma sprayed coatings were prepared on carbon steel substrates with Ti and B₄C as starting materials. Two kinds of gases (Ar and N₂) were used as feeding gases for powders, respectively. 10 wt.% Cr was added in the powders as binder to increase the bond strength of the coating. The phases, microstructure, micro-hardness and corrosion polarization behavior in 3.5 wt.% NaCl solution of the two coatings were studied. The results show that TiN-TiB₂ coatings were prepared under both conditions. The two coatings have typically laminated structure. However, the coating prepared with Ar as feeding gas has higher porosity and some unmelted Cr particles. It also contains certain content of titanium oxides. The microhardness of coating prepared with Ar as feeding gas is lower due to its higher porosity, unmelted Cr particles and some amounts of TiO₂. The corrosion resistance of TiN-TiB₂ coating prepared with Ar as feeding gas in 3.5 wt.% NaCl solution is worse than that of the coating prepared with N₂ as feeding gas. Yet the corrosion resistance of reactive plasma sprayed TiN-TiB₂ coating is improved greatly compared with that of carbon steel. The thermodynamic analysis of reactive plasma spraying process is also discussed.

Direct current electrodeposition of Co–P alloy coatings were carried out using gluconate bath and they were characterized by employing techniques like XRD, FESEM, DSC and XPS. Broad XRD lines demonstrate the amorphous nature of Co–P coatings. Spherical and rough nodules are observed on the surface of coatings as seen from FESEM images. Three exothermic peaks around 290, 342 and 390°C in DSC profiles of Co–P coatings could be attributed to the crystallization and formation of Co₂P phase in the coatings. As-deposited coatings consist of Co metal and oxidized Co species as revealed by XPS studies. Bulk alloy P(P^δ-) as well as oxidized P(P⁵⁺) are present on the surface of coatings. Concentrations of Co metal and P^δ- increase with successive sputtering of the coating. Observed microhardness value is 1005 HK when Co–P coating obtained from 10 g L^-1NaH₂PO₂ is heated at 400°C that is comparable with hard chromium coatings.

The influence of Mn²⁺/Ni²⁺ mole ratio in electrolytes on the Ni–Mn alloy deposits was studied. The electrodeposition mechanism of Mn with Ni is analyzed by the cyclic voltammogram (CV) and an "induced co-deposition" mechanism is proposed for Ni–Mn alloy electrodeposition. The results show that the Mn content in Ni–Mn alloy deposit and the hardness increased with the increase of Mn²⁺/Ni²⁺ mole ratio in electrolytes. When the Mn²⁺/Ni²⁺ mole ratio in bath was 2/1, the corrosion current density of the deposit coating was the lowest and the corresponding corrosion potential was higher, and under these conditions the coating with a Mn content of 1.20 wt.% showed good corrosion resistance. The scanning electron microscopy (SEM) of the alloy coatings exhibited that the morphology of Ni–Mn alloy coatings were different from Pure Ni coating, and when Mn²⁺/Ni²⁺ was 2/1, the surface was compact and homogeneous.

Ni–W alloy coatings are electrodeposited with direct and pulse current using gluconate bath at pH5. Effects of direct current (DC) and pulse current (PC) on structural characteristics of the coatings have been investigated by energy dispersive X-ray spectroscopy (EDXS), X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), differential scanning calorimetry (DSC) and X-ray photoelectron spectroscopy (XPS). EDXS shows that W contents are 13.3 and 12.6 at.% in DC and PC (10:40) Ni–W coatings, respectively. FESEM analysis exhibits the homogeneous coarse nodular morphology in DC plated deposits. DSC studies reveal that Ni–W coatings are thermally stable up to 400°C. XPS studies demonstrate that DC plated coating has significant amount of Ni and W in elemental form along with their respective oxidized species. In contrast, mainly oxidized metals are present in the as-deposited coatings prepared with PC plating. The microhardness of pulse current (100:400) deposited Ni–W coating is about 750 HK that is much higher than DC plated coating (635 HK). Heat treatment of the deposits carried out at different temperatures show a significant increase in microhardness which can be comparable with hard chromium coatings.

This paper aims at improving the hardness and wear resistance of Austenitic 316L Stainless Steel (SS) by Plasma-assisted Low Temperature Carburizing (PLTC) process. The process has been employed in austenitic 316L SS for achieving carbon supersaturated phase, the so-called “S Phase”. The microstructure of the treated specimens was characterized by Optical microscopy, Scanning Electron Microscopy (SEM) and X-Ray Diffraction (XRD). The results showed evidences of expanded austenite phase and formation of “S phase” at a temperature of 460${}^{\circ }$C with 10% of methane (CH${}_4)$ and 90% of hydrogen (H${}_2)$ at a pressure of 1mbar for a time period of 20h. The hardness of the specimen was evaluated as 1030HV using Vickers microhardness setup. The wear behavior of plasma treated specimen was studied using pin on disc test at ambient condition and the results are discussed. Wear rate in PLTC 316L SS was observed to be low when compared with the wear rate of the untreated 316L SS specimen. The PLTC 316L SS specimen is subjected to ASTM A262 oxalic acid etch test to study the intergranular corrosion behavior. The “step” formation was observed in the SEM micrographs which reveal the retention of corrosion resistance in the specimen.

In this work, an attempt has been made to optimize the process parameters on turning operation of INCOLOY 800H, with the aid of cryogenically treated (24h, 12h and untreated) multi-layer chemical vapor deposition (CVD) coated tools. The influencing factors like cutting speed, feed rate, depth of cut and cryogenic treatment were selected as input parameters. Surface roughness, microhardness and material removal rate (MRR) were considered as output responses. The experimentation was planned and conducted based on Taguchi L₂₇ standard orthogonal array (OA) with three levels and four factors. Multi-criteria decision making (MCDM) methods like grey relational analysis (GRA) and technique for order preference by similarity to ideal solution (TOPSIS) have been used to optimize the turning parameters in this work. Similar results were obtained from these MCDM techniques. Analysis of variance (ANOVA) was employed to identify the significance of the process parameters on the responses. Experimental research proved that machining performance could be improved efficiently at cutting speed is 55m/min, feed rate is 0.06mm/rev, depth of cut is 1mm and 24h cryogenically treated tool. Tool wear was analyzed for the cutting tool machined at the optimum cutting condition with the help of scanning electron microscope (SEM) and energy dispersion spectroscopy (EDS). Dry sliding wear test was also conducted for the optimal condition. The percentage improvement in machining performances is 12.70%.

This paper discusses the synthesis and characterization of Ni-TiN nanocoatings prepared by computer-controlled pulsed electrodeposition method. The influence of plating parameters on the microstructure, microhardness, and properties of the coating was investigated using transmission electron microscopy, atomic force microscopy, X-ray diffraction spectroscopy, scanning electron microscopy, and friction wear testing technique. The results showed that the Ni-TiN nanocoating synthesized at 4A/dm² current density exhibited an optimum microhardness and TiN content of 984.7HV and 8.69wt.%, respectively. Ni-TiN nanocoatings prepared at different pulse frequencies grew as face-centered cubic structures along different directions, and average grain diameters of Ni and TiN in the nanocoating prepared at 200Hz were 87.2 and 34.6nm, respectively. The nanocoating prepared at 20% duty cycle showed an optimum microhardness and average wear of 980HV and 7.56mg/mm².

The microstructural features and microhardness of ZrB₂-reinforced Ti-SiC coatings on Ti-6Al-4V substrate were studied. The deposition of these coatings was achieved via laser cladding technique. A 4.0kW fiber-delivered Nd: YAG laser was used to deposit the coatings on the titanium substrate at a laser power of 700W and a laser scan speed of 0.8m/min. An initial Ti-SiC coating was deposited with no ZrB₂ addition followed by deposition of two other coatings with the incorporation of ZrB₂ powder at 5 and 10wt.%. The coatings were examined using scanning electron microscope (SEM) coupled with energy dispersive spectroscopy. SEM images of Ti-SiC-ZrB₂ coatings revealed good metallurgical bond between the coatings and the substrate and also a significant increment in dendritic formation and inter-dendritic eutectics during solidification within the $\alpha$-Ti matrix, exhibiting the presence of newly formed phases as the weight percentage of ZrB₂ increased. Back-scattered electron images also showed the dissolution effect of SiC particles, as the particle–matrix bond strength is influenced by ZrB₂ addition. Furthermore, the microhardness of the Ti-SiC coating was enhanced with increasing ZrB₂ weight percentage. X-ray diffraction analysis revealed dominant compounds formed during laser material processing. This study deepens the knowledge of possible microstructural features associated with Ti-SiC-ZrB₂ cermet coatings.

The wear behavior of untreated and WC-12% Co laser alloyed nodular cast iron samples were analyzed using a high temperature pin-on-disc tribometer. Response surface methodology (RSM) based Box–Behnken technique was employed to minimize the sum of trials and to develop a mathematical model for the input process parameters namely sliding velocity, temperature and load. The interaction effects of the process parameters were investigated using the developed model. Further, the developed model was analyzed using analysis of variance. Scanning electron microscopy and energy dispersive spectrum were used for characterization. Laser alloyed samples showed a minimum wear rate ($0.3379\times 10^{-3}$ to $0.9537\times 10^{-3}$mm³/m) and friction coefficient (0.10 to 0.39) compared to untreated samples. The results of the validation test showed that the experimental results agreed well with predicted results of the developed mathematical model.

The present work reports the deposition of a quaternary Ni-B-W-Mo coating on AISI 1040 medium carbon steel and its characterization. Quaternary deposits are obtained by suitably modifying existing electroless Ni-B bath. Composition of the as-deposited coating is analyzed by energy dispersive X-ray spectroscopy. The structural aspects of the as-deposited and coatings heat treated at 300${}^{\circ }$C, 350${}^{\circ }$C, 400${}^{\circ }$C, 450${}^{\circ }$C and 500${}^{\circ }$C are determined using X-ray diffraction technique. Surface of the as-deposited and heat-treated coatings is examined using a scanning electron microscope. Very high W deposition could be observed when sodium molybdate is present in the borohydride-based bath along with sodium tungstate. The coatings in their as-deposited condition are amorphous while crystallization takes place on heat treatment. A nodulated surface morphology of the deposits is also observed. Vickers’ microhardness and crystallite size measurement reveal inclusion of W and Mo results in enhanced thermal stability of the coatings. Solid solution strengthening of the electroless coatings by W and Mo is also observed. The applicability of kinetic strength theory to the hardening of the coatings on heat treatment is also investigated. Corrosion resistance of Ni-B-W-Mo coatings and effect of heat treatment on the same are also determined by electrochemical techniques.

The Q235 steel was covered by Fe–Al–Nb alloyed coating to improve the mechanical properties of the Q235 steel. This double glow plasma surface metallurgy (DGPSM) surface modification technique was carried out at 1023K and pressure of 38Pa for 4.5h. The surface morphology represented the typical Volmer–Weber mode, an island structure which was accumulated by numerous small particles, and most of the angles formed between three islands were about 120${}^{\circ }$ where there was no appreciable defect. Meanwhile, in the cross-sectional morphology of the Fe–Al–Nb coating, there was a deposition layer, a diffusion layer and two transition regions between the different adjacent interfaces, and the coating approximate 17$\mu$m was found to be metallurgically adhered to the Q235 steel. The basic mechanical properties of the Fe–Al–Nb coating and Q235 steel including the hardness, elastic modulus and friction performance were measured and compared. The results showed that the formation of Fe₃Al, FeAl, and Fe₂Nb intermetallic compounds and Nb carbides in the coating can enhance the mechanical properties of the treated sample. The nanoindentation tests indicated that the hardness and elastic modulus of Fe–Al–Nb coating were 8.08GPa and 260.03GPa which were much higher than Q235 steel. The sliding friction tests showed that Fe–Al–Nb coating significantly improved the friction performance of Q235 steel at the speed of 300, 600 and 900rpm with load 320g for 15min.