Browsing by Author "Yahaya, Taiwo"
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Item Analysis of intergranular carbide precipitate in haz of martensitic stainless steel(Taylor’s University, Malaysia, 2017) Ahmed, Ismaila Idowu; Adebisi, Jeleel Adekunle; Yahaya, Taiwo; Abdulkareem, Sulaiman; Sherry, Andrew H.Analysis of intragranular carbide precipitate in the Heat Affected Zone (HAZ) of Martensitic Stainless Steel (MSS) weldment was carried out. Low carbon grade martensitic stainless steel weldment subjected to four point bend test in simulated sweet crude environment was analysed with Transmission Electron Microscope (TEM). The optical microscopy of the failed sample revealed the presence of intergranular cracks on both sides of the weldment in the HAZ. Electron transparent sample for TEM was prepared from the HAZ of the weldment using extraction replica technique. The examination of TEM specimen in imaging mode revealed the presence of precipitates on grain boundaries. The compositional analysis of the precipitates was carried out with Energy Dispersive X-ray (EDX). The result of EDX analysis showed the presence of chromium and molybdenum, this suggests, the precipitates were carbides of the form M23C6. The study therefore upholds sensitisation as the mechanism behind the intergranular cracks observed in the HAZ of the MSS weldment.Item Assessment of Crack Propagation Mode in Martensitic Stainless Steel HAZ with Electron Back Scatter Diffraction: Effects of Environmental Variables(Universitatea Politehnica Timisoara (UPT), Romania, 2016-05) Ahmed, Ismaila Idowu; Adebisi, Jeleel Adekunle; Yahaya, Taiwo; Aremu, Ishaq Na'Allah; Sherry, Andrew H.In this study, an assessment of crack propagation mode in martensitic stainless steels heat affected zone was carried out with electron back scatter diffraction (EBSD) with focus on the effect of environmental variables. Girth welded samples were subjected to four point bend tests in sour and sweet environments. Scanning electron microscope and electron back scatter diffraction technique were both used to study the crack propagation mode and interaction of crack tip with microstructures. Study showed that sample tested in sour environment failed with transgranular cracking and samples tested in sweet environment failed with intergranular stress corrosion cracking mode. The proposed mechanism for the failure was sulphide stress corrosion cracking and intergranular precipitation of carbide by sensitisation process respectively. The correlation between crack path and grains misorientation was studied with aid of EBSD technique.Item Assessment of Deformation Twinning in Cold Rolled Austenitic Stainless Steels with Electron Back Scatter Diffraction(Faculty of Engineering and Technology, University of Ilorin, 2014-06-09) Ahmed, Ismaila Idowu; Wright, David; Adebisi, Jeleel Adekunle; Aremu, Ishaq Na'Allah; Yahaya, Taiwo; Quita da Fonseca, JoaoDeformation twinning has traditionally been studied with Transmission Electron Microscopy (TEM). In this study, an assessment of deformation twinning in Austenitic Stainless Steel (ASS), type 304L, cold rolled to 20% reduction was investigated using Scanning Electron Microscopy (SEM) and Electron Back Scatter Diffraction (EBSD) techniques rather than the conventional TEM. The study revealed the presence of deformation twins in the cold rolled grains of ASS. It emerged from the study that the deformation twins observed may facilitate localised heterogeneous deformation and development of internal stresses within the grain.Item Carbo-Nitriding of AISI 1018 Steel Plate with Animal Horn(Mechanical Engineering, University of Ibadan, 2016) Ahmed, Ismaila Idowu; Mohammed, Aminat T.; Adebisi, Jeleel Adekunle; Yahaya, Taiwo; Ambali, I. O.The research on the carbonitriding of AISI 1018 steel with animal horn was carried out with the aim of converting waste to wealth through re-use approach of waste management. Cattle horn was processed into two different morphologies namely: powder and flakes. Carbonitriding heat treatment was carried at 850oC and 450oC for carburizing and nitriding dominated processes respectively. Vickers hardness measurement was carried out on samples heat treated with horn powder and flakes. Optical metallography was carried out on carbonitrided sample for microstructural examination following the heat treatment. The results of the investigation showed that hardness gradient occurred with higher hardness value at the near surface and decreasing towards the core. Sample heat treated with horn flakes showed higher hardness than those that was heat treated with horn flakes. Microstructural examinations of carbonitrided samples revealed the presence of martensite and retained austenite. From the result of study, it was concluded that the high hardness values observed was attributed to the diffusion of carbon and nitrogen atoms to the interstices of the host atom. Again the solute atoms helps to stabilise austenite microstructures which later transformed to martensite observed in the optical micrographs.Item Combustion Characteristics of Bio-Degradable Biomass Briquettes(Taylor’s University, Malaysia, 2018-09) Abdulkareem, Sulaiman; Akeem, B. A.; Ahmed, Ismaila Idowu; Ajiboye, Tajudeen K.; Adebisi, Jeleel Adekunle; Yahaya, TaiwoThis paper reports on the combustion characteristics of biodegradable biomass briquettes prepared from charcoal, sawdust and sugarcane bagasse. The three materials were mixed in respective ratio of 20:20:60, 20:30:50, 20:40:40, 20:50:30 and 20:60:20. The briquettes were produced using Budenberg dial gauge hydraulic compression machine with the formation of briquettes under 64 MPa pressure with 120 seconds dwell time. Combustion characteristics such as proximate analysis, fuel-burning rate, fuel ignition time and afterglow time of the produced briquettes were determined. Results show that briquette with sample composition of 20:50:30 has better calorific value of 24613.69 kJ/kg and sample with ratio 20:30:50 has lowest calorific value of 22500.3 kJ/kg, while sampling with ratio 20:30:50 has better physical properties with shatter resistance of 99.61% and porosity index value of 47.40%.Item Effect of welding variables on mechanical properties of low carbon steel welded joint(Advances in Production Engineering & Management, University of Maribor, 2014) Talabi, Segun Isaac; Owolabi, Oluwasegun Biodun; Adebisi, Jeleel Adekunle; Yahaya, TaiwoThis paper discussed the effect of welding variables on the mechanical prop-erties of welded 10 mm thick low carbon steel plate, welded using the Shield-ed Metal Arc Welding (SMAW) method. Welding current, arc voltage, welding speed and electrode diameter were the investigated welding parameters. The welded samples were cut and machined to standard configurations for tensile, impact toughness, and hardness tests. The results showed that the selected welding parameters had significant effects on the mechanical properties of the welded samples. Increases in the arc voltage and welding current resulted in increased hardness and decrease in yield strength, tensile strength and impact toughness. Increasing the welding speed from 40-66.67 mm/min caused an increase in the hardness characteristic of the welded samples. Initial decrease in tensile and yield strengths were observed which thereafter increased as the welding speed increased. An electrode diameter of 2.5 mm provided the best combination of mechanical properties when compared to the as received samples. This behaviour was attributed to the fact that in-creased current and voltage meant increased heat input which could create room for defect formation, thus the observed reduced mechanical properties.Item Effects of Soaking Time and Cold Work on Sensitisation of Austenitic Stainless Steels(University of Novi Sad, Serbia, 2015-10-20) Ahmed, Ismaila Idowu; Adebisi, Jeleel Adekunle; Yahaya, Taiwo; Abdulkareem, SulaimanThe effects of soaking and coldworks on sensitisation of austenitic stainless steels were studied. Annealed and samples coldworked to 20% and 40% were subjected to sensitisation heat treatment at 650 C for 24 and 72 hours. Metallographic analysis carried out showed that sensitisation occurred in both annealed and coldworked samples which manifested as ditches. Soaking for 72 hours showed more ditches than 24 hours. Intergranular ditches were more prevalent in annealed and lower coldworked samples. In contrast, heavily coldworked samples were more susceptible to transgranular carbide precipitation evident by ditches on slip bands and recrystallised grains.Item Microstructural Correlation of Hardness Profile in Martensitic Stainless Steel Weldment(Springer, 2016-02-10) Ahmed, Ismaila Idowu; Adebisi, Jeleel Adekunle; Yahaya, Taiwo; Abdulkareem, Sulaiman; Sherry, Andrew H.The correlation between microstructures and hardness profiles in low carbon martensitic stainless steel girth weldment were investigated. Optical microscopy and a scanning electron microscope equipped with electron back scatter diffraction system were used for assessment of microstructural phases, grain sizes, and grain misorientation across the weldment. The hardness value fluctuated between the peak and lowest values in the heat-affected zone of the weldment. The hardness profile observed is consistent with microstructural evolution across the weldment. The low hardness value observed in the weld metal was attributed to the large proportion of ferrite introduced by the superduplex filler metal used for the fabrication and grain coarsening caused by prolonged cooling of the weld metal. The electron backscatter diffraction data showed that higher grain sizes occurred in the weld metal and this is consistent with the highest degree of misorientation and recrystallisation observed in the weld metal than parent and HAZ region of weldment.Item Numerical Modelling of Petroleum Underground Storage Tank Dip Gauge(SAGE, 2014-05) Ahmed, Ismaila Idowu; Abdulkarim, Kazim Olawale; Yahaya, Taiwo; Aremu, Ishaq Na'Allah; Alabi, Abdul Ganiyu FunshoThis work describes numerical modelling of underground hydrocarbon storage tank dip gauge. The work was carried out at the request of a petroleum company faced with predicament, whereby three underground tanks, for the storage of hydrocarbon products, namely, Petroleum Motor Spirits, Automotive Gas Oil, and Dual Purpose Kerosene, were fully installed and buried in the earth without provision for the fluid measuring gauge. The objective was to design and fabricate a dip gauge with the design capacity of measuring up to 30,000 L of hydrocarbon from the underground storage tank. To achieve the objective of designing an accurate and reliable gauge, mathematical analysis of the available data of tanks was carried out using Newton–Raphson iteration method. A model dip gauge was designed and calibrated with the results of mathematical analysis. The dip gauge was designed with measurement capability between the range of 200–15,886 L and 400–31,765 L of hydrocarbon in the smaller and bigger tanks, respectively. Aluminium alloy 6063-T6 was used for fabrication of the gauge on account of its excellent strength and good corrosion resistance in relevant hydrocarbon environment.Item Physical and Mechanical Characteristics of Charcoal, Sawdust and Sugarcane Bagasse as Solid Fuel Materials(Malaysian Technical University Network, 2017-12-19) Abdulkareem, Sulaiman; Badejo, H. A.; Ahmed, Ismaila Idowu; Adebisi, Jeleel Adekunle; Yahaya, Taiwo; Ajiboye, Tajudeen K; Abdulrahim, A. T.This paper reports on the physical and mechanical characteristics of briquettes produced from charcoal, sawdust and sugarcane bagasse using molasses with sodium silicate as binders. Charcoal, sawdust and sugarcane bagasse were mixed in a respective ratio of 20:20:60, 20:30:50, 20:40:40, 20:50:30 and 20:60:20. The briquettes were produced using Budenberg dial gauge compression machine, with a pressure of 64 MPa at 120 seconds dwell time. Physical properties (relaxation ratio, compaction ratio and shattering index) and mechanical property (compressive strength) of the produced briquettes were investigated. Results show that briquette with sample composition of 20:30:50 has better physical properties with a relaxation ratio of 1.562, a compaction ratio of 7.573 and shatter index of 99.6%, while sample with ratio 20:40:40 has the highest compressive strength of 55.43 kN/m2.Item Potential of Cow Horn for Carbonitriding Treatment of Steel(Springer, 2018-01-29) Ahmed, Ismaila Idowu; Mohammed, Aminat T.; Abdulkareem, Sulaiman; Yahaya, Taiwo; Ambali, I. O.; Bamidele, L. B.; Adebisi, Jeleel AdekunleThe potential of carbonitriding treatment of steel with cow horn was investigated in line with abattoir waste to wealth approach of waste management. The objectives of the study included processing of cow horn into different morphologies namely: powder and flakes for carbonitriding heat treatment, and, chemical analyses of cow horn with Energy Dispersive Spectroscopy (EDS) and X-ray Diffraction (XRD) techniques to determine the chemical composition and phases of cow horn respectively. The heat treatment was carried out at 850 and 450 °C for carburizing and nitriding dominated processes respectively. Vickers hardness measurement was carried out to determine the hardness profile on carbonitrided samples. Optical metallography was carried out for microstructural examination and to investigate phase contrast between the case and core of carbonitrided sample. The result of hardness test observed is consistent with the case hardening profile with higher hardness value at near surface decreasing towards core. Sample heat treated with horn flakes showed higher hardness than those with horn powder. Microstructural phase contrast showed delineation of the hardened case and soft inner core. The high hardness of case was attributed to diffusion of carbon and nitrogen atoms from the cow horn to iron interstices. This supposition was corroborated by detection of carbon and nitrogen with EDS and XRD tests. It was therefore concluded that cow horn could be processed as candidate materials for carbonitriding of steel.Item Stress corrosion cracking of austenitic stainless steel in chloride environment(Nigerian Journal of Engineering, Faculty of Engineering, Ahmadu Bello University, 2015-03) Ahmed, Ismaila Idowu; Alabi, Abdulganiyu; Odusote, Jamiu Kolawole; Aremu, Ishaq; Adebisi, Jeleel Adekunle; Yahaya, Taiwo; Talabi, Segun Isaac; Yahya, Raheem; Lyon, S. B.This study was carried out to assess the effect of applied potentials on stress corrosion cracking (SCC) of Austenitic Stainless Steel (ASS). Type 304L in a potentiostatically controlled chloride environment at ambient temperature. The stress corrosion cracking tests were carried out on annealed ASS using a Slow Strain Rate Test (SSRT) technique in sodium chloride solution acidified with hydrochloric acid at ambient temperature. Analyses of failed specimens were carried out using optical microscope. The study showed that plastic elongation, ultimate tensile strength and time to failure decrease as the applied potential increases during the slow strain rate test. The study showed that immunity of ASS to chloride SCC was improved when the electrochemical potential was maintained in the primary passive potential range. Analysis of failed samples showed evidences of SCC.Item Stress Corrosion Cracking of Austenitic Stainless Steel in Chloride Environment(Faculty of Engineering, Ahmadu Bello University Zaria, 2015) Ahmed, Ismaila Idowu; Alabi, Abdul Ganiyu Funsho; Odusote, Jamiu Kolawole; Aremu, Ishaq Na'Allah; Adebisi, Jeleel Adekunle; Yahaya, Taiwo; Talabi, Segun Isaac; Yahya, Raheem Abolore; Lyon, Stuart B.This study was carried out to assess the effect of applied potentials on stress corrosion cracking of Austenitic Stainless Steels (ASS), Type 304L in a potentiostatically controlled chloride environment at ambient temperature. The stress corrosion cracking tests were carried out on annealed ASS using a Slow Strain Rate Test (SSRT) technique in sodium chloride solution acidified with hydrochloric acid at ambient temperature. Post-mortem analyses of failed specimens were carried using optical microscopy. The study showed that plastic elongation, ultimate tensile strength and time to failure decrease as the applied potential increases during the slow strain rate test. The study showed that immunity of ASS to chloride SCC was improved when the electrochemical potential was maintained in the primary passive potential range. Post-mortem analysis of failed samples showed evidences of SCC and ductile failure on the fracture surface.Item Stress Corrosion Cracking of Austenitic Stainless Steels in Potentiostatically Controlled Chloride Environments at Ambient Temperature(Universitatea Politehnica Timisoara (UPT), Romania, 2015-11-04) Ahmed, Ismaila Idowu; Yahaya, Taiwo; Adebisi, Jeleel Adekunle; Aremu, Ishaq Na'Allah; Alabi, Abdul Ganiyu Funsho; Lyon, Stuart B.In the earlier study carried out to assess the effect of applied potentials on stress corrosion cracking of Austenitic Stainless Steels (ASS), Type 304L in a potentiostatically controlled chloride environment at ambient temperature, the assessment of cracks in failed specimen was limited to optical microscope. In this present study, Scanning Electron Microscope (SEM) was used in addition to optical microscope to gain a better understanding of the Stress Corrosion Cracking (SCC) mechanism in the failed specimen. Stress corrosion cracking tests were carried out on annealed ASS using a Slow Strain Rate Test (SSRT) technique in sodium chloride solution acidified with hydrochloric acid at ambient temperature. Post-mortem assessments of failed specimens were carried out using both optical and SEM. The study showed that plastic elongation, ultimate tensile strength and time to failure decrease as the applied potential increases during the slow strain rate test. The study showed that immunity of ASS to chloride SCC was improved when the electrochemical potential was maintained in the primary passive potential range. Post-mortem assessment of failed specimens showed evidences of SCC and ductile failure on the fracture surface. The cross sectional analysis of the failed samples showed cracks that were predominantly transgranular stress corrosion cracks.