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.

Experimental Investigation of Laser Metal Deposited Al–Cu–Ti Coatings on Ti–6Al–4V Alloy

Abstract: The aim of this research is to study the effect of aluminum-based coatings on the new emerging surface properties, producing improved thermal, mechanical, tribological and metallurgical properties, which can withstand adverse environmental conditions using laser metal deposition technique. In this study, laser metal deposition was used to produce a hybrid coating on Ti–6Al–4V at a scanning speed of 0.8 m/min. The laser power of the process was also varied between 900 and 1000 W. The microstructure was characterized by using the scanning electron microscope (SEM) and an optical microscope (OPM). The mechanical properties of the samples were characterized using microhardness test. From the results, the higher the scanning speed, the more the microhardness of the samples.

Microstructural Characteristics and Hardness Property of Laser Cladded Ti and TiB 2 Nanocomposites on Steel Rail

Abstract: The laser cladding experiment was carried out on a two-powder loading hub laser machine at the Center for Scientific Innovation and Research, Pretoria, South Africa. Nanocomposites of Titanium and Titanium diboride was at ratio loaded and cladded on carbon steel surface. Metallurgical characterization of microscopic and macroscopic view was executed. The X-ray diffraction was taken with the PW1710 Philips diffractometer. XRD results of TiB 2 rich samples reveals peak phase of cubic Titanium diboride, hexagonal Titanium, cubic alpha-Iron, tetragonal Iron 2 boride and hexagonal Titanium diboride. XRD of even mix sample revealed clad phases of hexagonal Titanium and orthorhombic Titanium diboride. XRD of Ti rich clad revealed phases of cubic gamma-Iron-austenite, hexagonal Titanium, hexagonal titanium diboride, cubic Khamrabaevite and hexagonal alpha-Titanium phases. Sample 3 showed good XRD phases that influenced the property of the composites. The working parameters of laser power were from 1250 W to 1500 W and scanning speed of 1.0 to 1.2. m/min. The analysis showed a microhardness response range of 781 HV to 1254 HV 0.5 .Interesting phases and structures have been seen in the microstructures of the admixed powders. Pores and colouration pigments are vital factors influencing the properties of the microstructures. Properties of each powder has been used to form new properties of the admixed powders which has significant effects on the final microstructures of the composites. The homogeneous distribution of the reinforcements in the microstructures of the composites can be linked to the optimized parameters which in turn also enhance the mechanical properties of the composites.

Python Data Analysis and Regression Plots of Wear and Hardness Characteristics of Laser Cladded Ti and TiB 2 Nanocomposites on Steel Rail

Abstract: A predictive statistical correlation and relationship between the wear rate and the hardness was carried out. A linear and quadratic polynomial regression machine learning details of the factors relationships was studies and stated. An independent variable of hardness property and dependent variable of wear rate property of cladded Ti and TiB 2 on carbon steel were proposed. Both linear and quadratic models revealed insignificant lack of fit with their degree of freedom being 3 and 2 respectively. There variables terms are significant, and the models not aliased. The Adjusted R-squared in the model was given as 0.06613 in linear regression and 0.8883 in quadratic regression model summary. Analysis of variance design revealed the responses for the models of their sum of squares and mean of squares with resultant residual of squares values of 0.16318 of the linear regression and 0.0228 of the quadratic regression in a significant reduction postulation. The F-Value derived is significant with 0.75189 value in the linear regression and 7.94963 value in the quadratic regression. The result also correlates with the Python data analysis.The predictive equation for the linear and quadratic polynomial regression were given to enable predictive determination of dependent variable of the wear rate from their dependent values of the micro-hardness property values evaluation. A clear optimization relevance of higher order polynomial regression analysis of the quadratic for maximised analytical results were stated and emphasized.

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.