B.J. Abdul Aleem

Degradation of aluminum metal matrix composites in salt water and its control

Abstract Alloy Al 6013-20 Si in tempers O, F and T4 showed good resistance to corrosion in salt spray tests. The corrosion rate of the alloy decreased with increased exposure time due to the formation of boehmite (AlO·OH). Studies conducted in 3.5 wt.% NaCl solution containing suspended particles of polystyrene showed a linear increase in the erosion–corrosion rate with velocity. The localized attack was concentrated mainly on the Al 6013/SiC interface. A high dislocation density was observed at the Al 6013/SiC interface, which interfered with the formation of a homogeneous protective film of boehmite on the alloy surface. Addition of cerium chloride drastically suppressed the rate of corrosion. Sodium molybdate offered a lesser degree of protection compared to cerium chloride.

Dross formation during laser cutting process

Melt formation during laser cutting of metallic substrates is considered and the melt thickness is formulated using a lump parameter analysis. The droplet diameter is also predicted and compared with the experimental results. A CO2 laser with variable pulse frequency is used in the experiment. Oxygen, as assisting gas, impinging coaxially with the laser beam, is used at different pressures. SEM and XRD are carried out to obtain micrographs and oxide compounds formed in the dross. It is found that the liquid layer thickness increases with increasing laser output power and reduces with increasing assisting gas velocity. The droplet formed is spherical and the droplet size predicted agrees well with the experimental results.

Effect of environmental factors on the atmospheric corrosion of mild steel in aggressive sea coastal environment

The eastern coast of Saudi Arabia has one of the most corrosive environments in the world. Dhahran is therefore an ideal location for the study of atmospheric corrosion. One out of every seven cars in the region is corroded. The atmosphere is contaminated by SO2 and a high concentration of suspended particulate matter (SPM) containing sand, salt and carbon particles, exceeding the World Health Organization (WHO) and Middle East Environmental Protection Agency (MEPA) limits most of the time. Corrosion proceeds in the Dhahran atmosphere at a R.H. as low as 40 per cent. At locations close to the sea (1.5 Km), β‐FeOOH is the major corrosion product and α‐ and γ‐FeOOH with some aluminates, silicates and hydrocarbons the minor products. At a location remote from the sea α‐ and γ‐FeOOH are found to be the major corrosion products as shown by XRD and FTIR spectroscopy. The concentration of hydrogen ions, chloride ions and SO2 appears to control the corrosion process during the initial exposure period up to one year and the adsorption of anions on the corrosion product films in the later period.

Investigation into the properties of friction-welded aluminium bars

Abstract The replacement of copper by aliminium is inevitable for certain application in the electrical industry due to economic reasons. Whilst in the majority of cases, aluminium can be joined only by adhesive bonding, mechanical fastening and solid-phase welding techniques. Friction welding offers an alternative welding process for the joining the aluminium bars. Frinction welding is well known for its ability to weld aluminium to many metals and consequently is being considered seriously. The present study examines the friction welding of aluminium bars. Three welding parameters including welding time, speed of rotation and applied pressure are considered. To carry out a statistical analysis (factorial analysis) determining the affecting parameters on the mechanical properties of the resulting welds, each factor is considered at three levels. Metallurigical investigation is carried out using SEM and optical microscopy.

Effect of Temper on Seawater Corrosion of an Aluminum-Silicon Carbide Composite Alloy

Abstract The corrosion behavior of annealed (O), as-fabricated (F), and naturally age-hardened (T4) aluminum alloy Al 6013 (UNS A96013) with 20 vol% silicon carbide in particulate form (SiC[P]) was investigated in 3.5 wt% sodium chloride (NaCl) and in Arabian Gulf water. Of the three tempers, T4 showed the lowest corrosion rate (0.04 mpy and 2.61 mpy) in deaerated and aerated NaCl, respectively. The corrosion rate in seawater was slightly higher. Predominant forms of corrosion were pitting and intergranular corrosion. Formation of corrosion chimneys was observed. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and energy dispersive spectroscopy (EDS) showed intermetallic formation and the presence of a gelatinous film of aluminum hydroxide (Al[OH]3) of bayrite type. The higher corrosion resistance of the T4 temper resulted from finer and more homogeneously distributed precipitates compared to tempers F and O. In view of the the alloys good corrosion resistance and outstanding ult...

Laser gas‐assisted nitriding of steel: residual stress analysis

Purpose – The laser nitriding process is involved with high temperature heating and high cooling rates. This, in turn, results in high levels of thermal stresses in the heated region. Moreover, the residual stress in the heated region remains high after the completion of the heating process, which limits the application of the laser nitriding process. The purpose of this paper is to investigate thermal stresses development and residual stress levels in the nitrided region.Design/methodology/approach – The microstructural changes and residual stress development in the laser gas‐assisted nitrided zone are examined. Finite element modeling is carried out to predict temperature and stress fields in the laser nitrided layer. The indentation tests and X‐ray diffraction (XRD) technique are used to determine the residual stress levels while previously derived analytical formula is used to predict the residual stress levels in the nitrided region.Findings – The residual stress predicted attains values within 230 M...

Study into mechanical properties of TiN coating on Ti‐6Al‐4V alloy through three‐point bending tests

Purpose – To examine the mechanical properties of TiN PVD coated Ti‐6Al‐4V alloy through three‐point bending tests.Design/methodology/approach – Ti‐6Al‐4V alloy is cut in size and polished and cleaned chemically before TiN PVD coating process. INSTRON three‐point bending equipment is used to conduct the bending tests for TiN coated and uncoated workpieces. During the tests, the load and displacement characteristics were recorded. The tests were terminated when the coating failed. Micrographs of surface and crack sites were obtained by SEM.Findings – Coating failure occurs due to shearing effect on the tensile surface. The spalling and buckling of the coating on the compressive surface are observed. The compressive stress generated on the top surface (where the indent is in contact) did not cause adhesive failure of the coating. Moreover, cohesive cracks occur on the tensile surface of the coating. The crack ledge under the action of shear stress appears on the tensile surface of TiN coating and multi crac...

Corrosion behavior of a discontinuously reinforced composite in salt water environment

In this study, the corrosion behavior of Al 6092/17.5 SiC(p) alloy is investigated. The alloy offers a good resistance to corrosion in 3.5 wt% NaCl as shown by weight loss and electrochemical studies conducted in a smoothly stirred condition up to 70 C. The alloy also offered a strong resistance to corrosion in a salt spray chamber. The corrosion behavior of the alloy, however, declined with an increase in velocity, temperature, and addition of polystyrene particles in the electrolyte. The declining corrosion resistance is attributed to the cracking and breakdown of the protective boehmite layer at elevated temperatures, higher velocities, and impact of polystyrene particles. Microanalytical studies reveal the intermetallic precipitates to be the preferred sites for initiation of pits. The alloy offers good service prospects in a marine environment at controlled flow velocities and temperatures.

Investigation into nitrided spur gears

The cold forging method has been widely used in industry to produce machine parts. In general, gears are produced by shaping or hobbing. One of the shaping techniques is precision forging, which has several advantages over hobbing. In the present study, cold forging of spur gears from Ti-6A1-4V material is introduced. To improve the surface properties of the resulting gears, plasma nitriding was carried out. Nuclear reaction analysis was carried out to obtain the nitrogen concentration, while the micro-PIXE technique was used to determine the elemental distribution in the matrix after forging and nitriding processes. Scanning electron microscopy and x-ray powder diffraction were used to investigate the metallurgical changes and formation of nitride components in the surface region. Microhardness and friction tests were carried out to measure the hardness depth profile and friction coefficient at the surface. Finally, scoring failure tests were conducted to determine the rotational speed at which the gears failed. Three distinct regions were obtained in the nitride region, and at the initial stages of the scoring tests, failure in surface roughness was observed in the vicinity of the tip of the gear tooth. This occurred at a particular rotational speed and work input.

Laser controlled melting of Haynes 188 alloy: surface with presence of TiC particles

Laser controlled melting of pre-prepared Haynes 188 alloy surface is carried out. A carbon film containing titanium carbide particles is formed at the workpiece surface prior to the laser treatment process. The metallurgical changes in the treated layer are examined, and the residual stresses formed at the treated surface are measured using the X-ray diffraction technique. It is found that laser treated surface is free from microcracks and surface asperities. The formation of carbonitride and nitride phases at the surface vicinity of the laser treated layer contributes to increasing hardness and dense layer formation at the surface. The residual stress formed at the surface is on the order of 590 ± 15 MPa.