Olawale S. Fatoba

Bio: Olawale S. Fatoba is an academic researcher from University of Johannesburg. The author has contributed to research in topics: Microstructure & Titanium alloy. The author has an hindex of 11, co-authored 67 publications receiving 356 citations. Previous affiliations of Olawale S. Fatoba include Vaughn College of Aeronautics and Technology.

Effect of punch force on the upsetting deformation process using three-dimensional finite element analysis

Abstract: Forging is one of the conventional shaping technologies that is widely used for the manufacture of quality products for various industrial applications. The process involves the mechanical application of a punching force to deform a material to the desired shape and improved properties. In most cases, the manufacture of quality products depends on the experience of the designer and trial and error method thus making the process wasteful and costly. The present study reports on the application of finite element method (FEM) for the analysis of the effect of punch force on the stress/strain distribution during the deformation process as a step towards the reduction of trial and error methods in practice. The results show that increase in the punch force leads to inhomogeneity in the strain/stress distribution due to change in the deformation temperature resulting from the internal heat generated during plastic deformation stage and the frictional force at the punch-workpiece interface. It is also observed that the maximum effective strain occurs at the center of the deformed sample and the maximum effective stress occurs at the low effective strain regions. Moreover, the friction parameter increases as the punch force increases.

The Effects of Rapid Cooling on the Improved Surface Properties of Aluminium Based Coatings by Direct Laser Deposition

Abstract: The deterioration of materials during industrial application poses a serious threat to the materials structural integrity. A material’s susceptibility to wear and surface damage can be reduced by alteration of its surface chemistry, morphology and crystal structure. Therefore, modification of surface properties plays an important role in optimizing a material’s performance for a given application. Modern industrial applications require materials with special surface properties such as high hardness, wear and corrosion resistance, therefore materials engineers are vital to regularly examine how the microstructure of a material can be altered. Aluminium-based alloys have a wide application in the automotive, domestic and aerospace industries due to their excellent mechanical properties such as good weldability, sound castability and outstanding resistance to corrosion. The purpose of this research is to enhance inherent properties of the materials to create new products or improve on existing ones. The most effective engineering solution to prevent or minimize such surface region of a component is done by fibre lasers. It was concluded that Hypereutectic Al-Si alloys having transition metals are exceptional materials due to their specific properties. The addition of Cu, Fe, Cr, Si, Mg and Ni to Al-based alloys can improve the mechanical properties at both ambient and elevated temperatures.

Numerical modelling and microstructural evolution of hybrid Ti-6Al-4V/Ti-Al-Si-Cu composite coating

Abstract: Additive manufacturing is a commercially competitive manufacturing technique with the possibility of altering the entire perception of design and fabrication It offers suitable capabilities for the building and repairing applications in the aerospace industry, which usually requires high level of accuracy and customization of parts which usually use materials known to pose difficulties in fabrication such as titanium alloys The major factors that determine the formation of the dendritic structure are the thermal gradients within the substrate during cooling and the cooling rates The rapid cooling and input of heat locally during the laser deposition process resulted in metallurgical modifications such as the formation of a complete martensitic structure, a mixture of columnar grains and layer of bands During the deposition process, the metal solidified, and the developed model enabled predictability of microstructural development and the sizes of the grain growth The 3D numerical investigation provided clarification and had substantial effects in the prediction of the overall resulting molten pool size and geometry size

Multi-objective optimization of process parameters in TIG-MIG welded AISI 1008 steel for improved structural integrity

Abstract: This study investigates a parametric multi-objective optimization of the Tungsten Inert Gas-Metal Inert Gas (TIG-MIG) hybrid welding of AISI 1008 mild steel joints. A combined grey relational system theory and the Taguchi method was used for process optimization towards achieving a set of process parameter that maximizes both ultimate tensile strength and 0.2% yield strength for structural applications. An L-9 orthogonal array based on the Taguchi method was adopted for the experimental design matrix. Grey relational grading system was used to establish a single grade for the responses. Mathematical models for first- and second-order regressions were developed and optimum process parameter combination that optimizes the response was obtained. From the results, the gas flow rate had the most significant influence on the responses with a percentage contribution of 39.77%. Also, the second-order regression models had a higher coefficient of determination (R2) compared to the first-order regression for the two responses and, thus, represents the best fit for the process. The grey relational grade was improved by 0.0489 through process optimization. The interactive effects of process parameters and their effects on the responses are also illustrated by response surface plots. This study shows the effectiveness of the grey relational grading system in achieving a multi-objective optimization for the TIG-MIG welding process.

Recent research and development status of laser cladding: A review

Abstract: In industries such as aerospace, petrochemistry and automobile, many parts of different machines are under environment which shows high temperature and high pressure, and have their proneness to wear and corrosion. Therefore, the wear resistibility and stability under high temperature need to be further improved. Nowadays, Laser cladding (LC) is widely used in machine parts repairing and functional coating due to its advantages such as lower dilution rate, small heat-affected zone and good metallurgical bonding between coating and substrate. In this paper, LC is introduced in detail from aspects of process simulation, monitoring and parameter optimization. At the same time, the paper gives a comprehensive review over LC material system as high entropy alloys (HEAs), amorphous alloy and single crystal alloy have been gradually showing their advantages over traditional metal materials in LC. In addition, the applications of LC in functional coatings and in maintenance of machine parts are also outlined. Also, the existing problems and the development trend of LC is discussed then.

Corrosion of metallic materials fabricated by selective laser melting

Abstract: Additive manufacturing is an emerging technology that challenges traditional manufacturing methods. However, the corrosion behaviour of additively manufactured parts must be considered if additive techniques are to find widespread application. In this paper, we review relationships between the unique microstructures and the corresponding corrosion behaviour of several metallic alloys fabricated by selective laser melting, one of the most popular powder-bed additive technologies for metals and alloys. Common issues related to corrosion in selective laser melted parts, such as pores, molten pool boundaries, surface roughness and anisotropy, are discussed. Widely printed alloys, including Ti-based, Al-based and Fe-based alloys, are selected to illustrate these relationships, and the corrosion properties of alloys produced by selective laser melting are summarised and compared to their conventionally processed counterparts.

Pulsed Nd:YAG laser cladding of stellite 6 on stainless steel

Abstract: A systematic research into the cladding of stellite 6 on stainless steel by pulsed Nd:YAG laser has been carried out. The effects of pulse energy, pulse frequency, powder mass flow rate and spot overlap on the clad layer height, dilution and heat-affected zone (HAZ) have been examined. It was found that both the clad height and penetration into the substrate increase with the pulse energy, spot overlap and pulse frequency, but the effects of these parameters on dilution are complex. The dilution reaches the lowest value (4%) at the incident energy of 18 and 25 J/ pulse, spot overlap of 89% and pulse frequency of 40 Hz. The powder mass flow rate of 22 g/min (for energy of 25 J/pulse and spot overlap of 83%) produces thick clad layer with low dilution but results in the formation of defects. The hardness of the clad layer decreases linearly with increasing dilution. No cracks have been found in single-track clad layers at a spot overlap of 89%, however, cracks occurred at lower spot overlap. These cracks were eliminated by the multi-track cladding when the track increment is less than 1/3 of the width of track, which is believed to be due to the remelting or heat treatment of the previous clad track by the subsequent track. The track bands in multi-track clad show coarser structure, higher element segregation and lower hardness.

Evaluation of microstructure, microhardness, and electrochemical properties of laser-deposited Ti-Co coatings on Ti-6Al-4V Alloy

Abstract: The marine, aerospace, and power machinery industries show progression in the application of titanium alloy components due to their good properties. However, the alloy exhibits poor thermal stability, low hardness, and poor tribological properties; as a result, the use of Ti6Al4V in various industries is restricted. Consequently, a search for surface improvement of Ti6Al4V alloy arose with the intention of enhancing its endurance. The use of laser metal deposition method by integrating chemical barrier coatings is considered as advantageous; therefore, an investigation aimed at surface improvement of Ti6Al4V by incorporation of Ti-Co coatings developed. To fabricate the coatings, a 3-kW continuous wave ytterbium laser system (YLS) was used, and to control the movement of the cladding process, a KUKA robot was attached to the system. The microstructure, corrosion, and mechanical properties of the titanium alloy-cladded surfaces were studied at different laser process parameters. To analyze the microstructure of the cross section, optical and scanning electron microscopy were employed. A laser power of 750 W and scanning rate of 1.2 m/min were found to be the optimum process conditions for a 60Ti-40Co alloy. When comparing the mechanical properties of the alloy and bare substrate, the alloy exhibited a significant increase in terms of the hardness. It was found to have 719 HV as compared to 301 HV which is that of the substrate, this indicates to an increase of 58.14% in the hardness. Lower laser scanning rates result in a larger fraction of hard-intermetallic phases which in turn lead to coatings with enhanced hardness levels. Furthermore, the yield strength and tensile strength of the coatings increased to maxima of 2.30 and1.66 GPa, respectively in comparison to the substrate, due to the addition of Co. Additionally, the corrosion rates of all the coated specimens were reduced as a result of the oxide films formed on the laser-coated Ti6Al4V alloy samples.