Showing papers by "Olawale S. Fatoba published in 2021"

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.

Experimental Investigation of TIG-welded AISI 1008 Carbon Steel

Abstract: Carbon steel is widely used in engineering applications due to its exceptional mechanical properties, and low cost. The fabrication technique employed to weld carbon steel plays a vital role in the final performance of the welded component when put into service. TIG welding is a generally accepted arc welding technique due to its ease and versatility coupled with its capacity to produce high-quality welds. It is the most desirable technique employed for welding plain carbon steel. This work aims to evaluate the influence of TIG welding process parameters on the mechanical and microstructural properties such as tensile strength, hardness, and microstructure of AISI 1008 carbon steel. The process parameters considered in this work were the TIG welding current, and gas flow rate. The tensile testing and the Vickers hardness testing have been carried out for the welded samples. The microstructural investigation was also carried out for the fusion zones (FZ) and the heat-affected zones (HAZ). The test results were analyzed, and emerging properties were compared for the various set of parameters. Welded specimen produced with 140 A, 15 L/mm had the highest hardness value. However, the highest average ultimate tensile strength of 432.89 MPA was produced from process parameters 180 A, 19 L/mm. Finer grain structures were seen in the fusion zones as compared to the heat-affected zones for all selected parameters.

Experimental study on microstructural evolution, mechanical property, and corrosion behaviour of laser additive manufactured (LAM) titanium alloy grade 5

Abstract: Additive manufacturing technique has become one of the more prominent manufacturing techniques over the years. The applications of this manufacturing technique are boundless as new process parameters of the operation affect the new structure of the components and give extended applications. The study experimentally investigates the effects of Ytterbium Laser System process parameters on the resultant microstructure of Ti-6Al-4V grade 5 alloy and reinforcement powders. The deposition process was conducted employing a 3 kW (CW) Ytterbium Laser System (YLS-2000-TR) machine, co-axial to the reinforcement powder. The laser scanning speed and power were varied between the intervals of 0.8–1.0 m/min and 900–1000 W. All other parameters kept constant were the rate of gas flow, the spot diameter, and the rate of powder flow. The composites (Ti-6Al-4V/Ti-Al-Si-Cu) produced by the DLMD technique were analysed using investigative techniques, namely, optical microscopy (OPM), scanning electron microscopy (SEM) aided with energy dispersive microscopy (EDS), X-ray diffraction analysis (XRD), microhardness testing, and corrosion rate analysis. From the analysis of the physical properties, the findings show that the geometric properties such as heat affected zone (HAZ) and dilution ratio of the composite samples were greatly impacted by the increase of the laser power of the DLMD technique, showing an increase in these attributes brought about by the interaction between the laser and the material. The addition of the copper (Cu) element enabled the movement of the copper (Cu) into the titanium (Ti) lattice structure resulting in the formation of beta titanium (β-Ti) microstructure. Increment 54.94% is associated with sample 5A which has the most enhanced microhardness of 770 HV1.0. Sample 6A had shown the most corrosion resistance improvement with 0.00062 mm/year equivalent to 31%.

Thermal Analysis and Impart of Temperature Distribution on the Performance of Additive Manufactured Titanium Alloy Based Composite Coatings

Abstract: Finite element numerical analysis can be used to solve problems of boundary values. The accuracy of model is depended on the meshing refinement. In aerospace industry, finite element analysis has been used by several researchers to know the influence of temperature distribution on the performance of additive manufactured component parts. Accuracy is better with finer mesh. Complex nature of the additive manufacturing process due to rapid heating and cooling made many researchers to adopt numerical investigation which is made easier than the experimental method. Proper modelling of the process must be thoroughly done for the numerical modelling results to be analyzed. The experiment of ternary titanium alloy of Ti-Al-Si-Cu was carried out with cladding machine of 3000 Watts (CW) Ytterbium Laser System (YLS-2000-TR). This machine is situated at the National Laser Centre in the Council of Scientific and Industrial Research (NLC-CSIR). The characterization was done using the standardization ASTM E3-11 procedure. The results shiw the impart of temperature distribution on the dendritic arm spacing in the microstructures. The rate of cooling imparts on the space between the dendritic arms. The more the space, the more the influence on the coating’s properties

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.

Influence of Rapid Solidification and Optimized Process Parameters on the Microstructural Evolution of Additive Manufactured Titanium Alloy Grade 5 Composite

Abstract: The study experimentally investigates the effects that Ytterbium Laser System process parameters, such as laser power, powder feed rate and traverse speed, has on the resultant microstructure of Ti- 6Al-4V grade 5 alloy. The deposition process was conducted employing a 3kW (CW) Ytterbium Laser System (YLS-2000-TR) machine, coaxial to the reinforcement powder. The laser scanning speed and power were varied between the intervals of 1-1.2 m/min and 900-1000 W. All other parameters kept constant where the rate of gas flow, the spot diameter, and the rate of powder flow. The microstructure was characterized by grain size and morphology by using Optical Microscopy (OM) and Scanning Electron Microscopy (SEM). The microstructural and mechanical properties were ascertained and the relationships with the process parameters were achieved. As a result of rapid cooling, the morphological features of α and α’ are distinctive and appear acicular. The structures appear coarsened. The metallurgy of the samples identifies with a morphology of multi-scale; with the coarsened alpha structures being reduced, plate-like, discrete and finer. The alpha grains closer to the fusion zone grew epitaxially, and the ones above these are acicular and lamellar. The results also indicated that slow traverse speeds increase the scale of columnar grains, while other process parameters were kept constant. Columnar microstructures became prevalent due to the dynamic temperature gradients/spikes, and sustainable cooling rates, pertaining to fabricating direct laser deposited Ti-6Al-4V grade 5 alloy. It was ascertained that by increasing the traverse speeds, the cooling rates increased, which resulted in a decrease in the width of the columnar grains.

Analysis of Geometrical Characteristics and Microstructural Evolution of Laser Deposited Titanium Alloy Based Composite Coatings

Abstract: The significance of additive manufacturing has been felt in aerospace industry, but the full implementation of this technique has not been adopted yet due to drawbacks in terms of quality and surface finishing. Quality and surface finishing need to be addressed for the full impact of additive manufacturing to be utilized in many industries, which in turn will impact on the economic aspect of nations. Additive manufacturing reliability must be addressed and research on reliability must be continuous in order to fully utilized all the advantages and benefits of this process in medical and aerospace industries for wide applications. The experiment of quartenary titanium alloy of Ti-Al-Si-Cu was carried out with cladding machine of 3000 Watts (CW) Ytterbium Laser System (YLS-2000-TR). This machine is situated at the National Laser Centre in the Council of Scientific and Industrial Research (NLC-CSIR). The characterization was done using the standardization ASTM E3-11 procedure. Optical images of the samples were taking via the cross-sectional areas of the samples using the standardization procedure ASTM E2228-10 standard with BX51M Olympus microscope. The microstructural evolution was carried out using the TESCAN machine with an X-MAX instrument with ASTM E766-14e1 standardization procedure.The metallurgical bond formed as a result of the melting between the base metal and the reinforcement powders was done by a reduced laser energy input in the range of 27 to 22.5 J/mm2 at samples fabricated at 900 W with increased scanning velocity. While samples fabricated at 1000 W showed decrease in laser energy input between 30 to 25 J/mm2 at increased scanning velocity. Narrow deposit width is achieved at higher scanning velocity due to small amount of reinforcement powders used during the laser material interaction. There is sharp reduction of 20.7% in clad height with 11% of copper to 12.1% in clad height reduction as the weight percent of copper is increased to 12% and further reduction to 10% in clad height as the weight percent of copper is increased to 13% with increased velocity between 1.0 to 1.2 m/min at lower laser power of 900 W. A slight reduction of 14.14 % was shown by specimen Ti-Al-9Si-3Cu. Different result was observed when the specimen was fabricated at 1000 W. The clad height reduction was in the range of 14.14 to 3.85 %.