Key Engineering Materials Vol. 796

Abstract: In this work, the wear behaviour of thin aluminium films deposited on stainless-steel substrate through rf magnetron sputtering is studied. The coefficient of friction and material loss are characterised as functions of the substrate temperature (Ts) of the deposited aluminium thin films. It was observed that due to the evolving microstructural and roughness properties of the films with the substrate temperature, the material behaviour of the films under extremely high wear loads significantly depend on the substrate temperature. The most significant coefficient of friction was observed at 60oC and 80oC, and highest material loss was recorded at 100oC. The material loss and variation of coefficient of friction were related to the morphology (porosity and roughness) of the sputtered aluminium thin films.

Abstract: Quaternary molten salt nitrate have been used very practically as medium for energy storage or heat transfer fluid in terms of energy recovery system. Quaternary molten salt nitrate is a mixture that can transfer heat to generate energy such as electricity. Mixed alkaline molten nitrate salt can act as a heat transfer fluid due to their advantageous in terms of heat recovery system due to high specific heat capacity, low vapour pressure, low cost and wide range of temperature in its application. This studies shows about determining the new composition of quaternary molten nitrate salts from different primary salts that can possibly give a high specific heat capacity with low melting point. The mixture of quaternary molten nitrate salts was then heated inside the box furnace at 150°C for four hours and rose up the temperature to 400°C for eight hours. Through heating process, the quaternary molten nitrate alkaline was completely homogenized. The temperature was then dropped to room temperature before removing the mixture from the furnace. The specific heat capacities of each sample were determined by using Differential Scanning Calorimeter, DSC. From the result of DSC testing, Sample 6 gives the highest point of specific heat capacity and low melting point which is 0.4648 J/g°C and 97.71°C respectively. In the nut shell, Sample 6 was chosen as a good mixture with good thermal properties that has a low melting point which is below 100°C but high specific heat capacity that may be a helpful in the application energy recovery system.

Abstract: The aim of the research is to subject the three different silanes to chemical and electrochemical investigations in other to determine the most efficient organic compound. Three types of hydrophobic silanes [Tris (Trimethylsiloxy) silyethyl] dimethylchlorosilane (Alkyl); Tridecafloro-1,1,2,2-tetrahydrooctyltrichlorosilane (FOTS) and Henicosyl-1,1,2,2-tetrahydrododecyltricholrosilane (FDDTS) are presented and investigated. The three silanes are of different composition but are deposited at the same parameters and conditions. The chemical investigation was studied through (attenuated total reflection Fourier-transform infrared (ATR-FTIR) and x-ray diffraction (XRD), while the electrochemical study was conducted through EIS using natural seawater electrolyte at room temperature. From the investigation techniques, only electrochemical impedance results show that FDDTS performed better than both Alkyl and FOTS. The chemical analysis showed the presence of hydrophobic silane on all the coated samples, and no distinction can be drawn from associated peaks.

Abstract: Milling process is the removal of unwanted materials so as to produce the required shape. The purpose of this study was to investigate the effect of milling process parameters and the cooling technique on corrosion behaviour and microhardness of TI-6AL-4V. Milling of Ti-6Al-4V was carried out using tungsten carbide cutting tool while varying spindle speed (120,150, and 180 rev/min), depth of cut (1, 1.5 and 2 mm) and the feed rate remained unchanged at 4.6 mm/min. Subsequent to milling, characterization of subsurface microhardness and corrosion behaviour was conducted. It was found that varying spindle speed and depth of cut had an impact on microhardness. Furthermore, it was noticed that the type of milling condition (flood and dry milling) affected the subsurface microhardness and the corrosion behavior. The corrosion resistance of the milled surface was generated at 180 rev/min and 150 rev/min for the dry and flood milling respectively. Furthermore, the most corrosion resistance was obtained at 2 mm and 1.5 mm depth of cut during dry and flood milling respectively.

Abstract: This paper presents a study on determining optimum parameters for lubrication in external grinding process. In the study, experiments were designed by using Taguchi technique. The experiments were set up with Oemeta Unimet AS 192 lubricant, Al₂O₃ grinding wheel and the workpiece material of tool steel 9CrSi. From the results of the experiments, the influences of coolant parameters on the surface roughness were analyzed. It was found that the concentration of lubricant was the most impact, the second is flow rate and the coolant pressure has little impact on the surface roughness. Also, the optimum parameters of lubrication for getting minimum surface roughness were proposed.

Abstract: Corrosion inhibition of martensitic stainless steel (MSS) in magnesium chloride was investigated in the absence and presence of calcium gluconate as corrosion inhibitor at ambient temperature. The effects of inhibitor concentration were studied using weight loss and polarization method. The results obtained showed that calcium gluconate acts as an inhibitor for martensitic stainless steel in MgCl and decreases the corrosion rate. The inhibition performance was found to increase with the increase in inhibitor concentration. The maximum inhibition efficiency obtained was 99 % at 2g/v inhibitor concentration, the adsorption of calcium gluconate on the surface of Martensitic stainless steel was found to obey Langmuir adsorption isotherm. However, the addition of solanum tuberosum extract in the inhibitor decreases the corrosion rate of martesitic steel significantly in chloride solution.

Abstract: Most of the corrosion inhibitors that are used in industry contain chemicals that are harmful to health and environment. Corrosion inhibitors derived from green sources are, therefore, believed to be a good option for replacing the chemical corrosion inhibitors. In this work, a green oleochemical corrosion inhibitor derived from Jatropha Curcas is introduced. The paper discusses the methodology of deriving the corrosion inhibitor as well as the experimental test conducted for evaluating its corrosion inhibition efficiency. The new oleochemical corrosion inhibitor was derived via two reactions. Jatropha oil was firstly saponified with sodium hydroxide to yield gras acid and glycerol, which was then esterified with boron fluoride in presence of excess methanol to produce the oil methyl esters, which is used as oleo-chemical corrosion inhibitor. To evaluate the oleo-chemical corrosion inhibitor, the corrosion rate of mild steel in NaCl corrosive medium with CO₂ is tested at static condition and two dynamic conditions, namely 500 and 1500 rpm. This is to simulate the transitional and turbulent flow in a pipeline. At each dynamic condition, the proposed corrosion inhibitor was tested at concentration dosages of 0, 50, 100, and 150 ppm. The experiments results revealed a good performance of the new oleochemical corrosion inhibitor. The inhibition efficiency was found to be highly affected by the concentration of corrosion inhibitor. Total corrosion inhibition of the mild steel was noticed by using 150 ppm at dynamic condition of 500 rpm.

Abstract: In the past, Electro Discharge Machining (EDM) process was well known in cutting extremely hard materials and fabricating complex shapes. Recently, EDM process has been hybridized to not only shape, but also coats the surface of workpiece material. In this study, the deposition of hard carbide and calcium-based oxides on the Zr-based bulk metallic glass (BMG) using hydroxyapatite mixed electro discharge coating (HAm-EDC) have been investigated. The aim is to enhance the biocompatibility and cell adhesion of the BMG as a potential implant. The chemical composition, morphology and thickness of the coated surface were characterized through Optical Microscope, Scanning Electron Microscopy (SEM), X-ray Spectroscopy (EDS) and X-ray Diffraction (XRD). Major hydroxyapatite elemental composition (Ca, P, O), carbides (ZrC, TiC) and oxides (ZrO, CaZrO₃) were formed on the treated BMG surface. A coating of about 23 µm thick was achieved. The addition of hydroxyapatite powder in the dielectric fluid enhances the Zr-based BMG surface quality by reducing the surface cracks and the crater size.

Abstract: Groove inaccessibility, top groove powder impedance, irregular sidewall powder delivery and lack of sidewall vertical irradiation have been reported as major limitations for the use of Laser Additive Technology (LAT) for narrow rectangular crack repair applications. As a result, most reported repair attempts were concluded unsuccessful. In the present work, a multi-track laser re-melt technique was developed for the repair of narrow rectangular cracks of sizes 2 and 3 mm, both 5 mm deep on 7 mm thick Ti-6Al-4V plates. The laser re-melt technique was carried out at controlled laser power, focal length, spot size, powder feed rate, gas flow rate and scanning speed. The repaired substrates were evaluated for defects through optical microscopy (OM) and scanning electron microscopy (SEM). The obtained results showed densely fused defect-free repaired substrates with good evolving microstructure.

Abstract: The gas, oil and water co-current flow in pipes either flow in separate layers or in the form of a mixture. Other than gas, the liquid mixtures are common during the transportation of oil. In liquid mixtures, one liquid acts as a continuous phase and the other liquid dispersed in it. The phase inversion in three-phase flow majorly depends on the superficial velocity of individual phases, the volume fraction of liquid phases in total liquid and the internal diameter of the pipe. Pipe bends and fittings are commonly used in pipe networks for the diversion and distribution of flow. The 90° elbow bends are commonly used in such systems, where they change the flow direction from horizontal to vertical and vice versa. For the case of horizontal to upward vertical flow, the bend offers restriction to the flow compared to the straight pipe. Therefore, the process of phase inversion gets effected upstream 90° bend. In the current work, the phase inversion process during three-phase horizontal flow upstream 90° bend has been studied. The internal diameter of the pipe was 0.1524 m and the bend radius to diameter ratio (r/d) was 1. The range of superficial velocities are 0.5-5, 0.08-0.4, and 0.08-0.4 for oil-gas and water respectively. The continuous liquid phase and its effect on pressure drop have been studied at various oil to liquid volume ratios (f_o). The results show the different oil-water relationships and the liquid holdup occurred due to the bend.